As we get old, some of us want to give away what we have experienced and tend to pontificate. We know the trip is getting close to the end and the train is slowing down and we have to get off in Paris - or some place with a name similar to that. Is there ham radio equipment in Paris? Seriously... thank you - I enjoy making these seat-of-the-pants videos and hope they are of some value to all of you.
May God give you many many more years to go ❤️❤️❤️🔥 my respect and i cud sit 🪑 on your class room for ever you remind me of my v.e back in the early 90s if you been a v.e they most to love you ....the way you have to teach is a gift from above sir ...i take my hat 🤠 off 73 ...
A trip to memory lane. In the late 1950s and early 60s I was pretty much involved with Ham radio. I always built my own transmitter and receiver but things changed in my life and I went to different path. In the 1980s I had a handheld transceiver, Icon or Yaesu, don't remember and one day I got home late from work and left it on the seat of my car and some passer by stole it. Since then I never went back to Ham radios. I even forgot my call.
We are on an up-cycle of the 2020 to 2031 sunspot cycle so now might be a good time to enjoy ham radio again. I don't care one bit if I make DX contacts but many people do. I have been at it pretty consistently since 1963, with a little slow-down here and there, but building in my passion and it helps keep me sane. 73
@@ElPasoTubeAmps Thank you for your reply. Very few people pay attention to the solar cycles. As you may know we are on the way to solar maximum (solar cycle 25) peaking sometime in 2024 or 2025. Maybe I could get an used Yaesu and get involved again. Tamitha Skov always talks about solar flux affecting ham radio propagation. Tamitha Skov is the space weather woman, check her out on UA-cam if you don't already follow her.
Hi David, Thanks for the tour of your AM and other gear. You really have some neat equipment. I have always been more interested in CW but from time to time I listen to the AM guys and enjoy their QSO's. I am still restoring R390, 390A, 391 and 392 receivers as a retirement FUN job after years with DEC Digital Equipment Corp. The only issue is my back is shot and the docs want to fuse L4, L5 and S1. I guess I need to stop and get it done while I am still young enough, I hope, to recover. Age 66 now. agn tnx fer nfo es 73 de WA4AOS dit dit
I love your AM gear, I only have cheap 27Mhz CB but it's the same. Good health to you. These old devices are great, I respect them a lot, it shouldn't be retired. good quality housings, good microphones, beautiful indicators, analog scales and bulbs are all amazing. I've always wanted a small tube or transistor radio station in old-fashioned housing. You can see it in some old movies, it was very mysterious, only for a select few. Health again :-)
Id give my left arm to sit and chat with you, your much like my late Father who was an ametuer extra class, also a radar engineer for Lockheed Aircraft Service back in 1954/78. Dad had alot of homebrew equipment but not to the level that you have, He also was a big 20m fan as well. Thank you for your tour!.
👍🏻 I'm leaving a quick comment here because the "Marilu" video has comments disabled. I just wanted to say how much I enjoyed the beautiful music and a quick glimpse at your very loving family. That's pretty rare in today's world. You have an outstanding channel and have educated my 57 yr. old solid-state brain about the fascinating world of vacuum tubes. You are a true wealth of knowledge! So... Thank You!! 🎙️ 73 from KD2MKZ a Current Captive of the PRNJ ("People's Republic of New Jersey) 😁
I realize why you had the comets off in your latest video. I just wouldn’t to thank your from the bottom of my heart for putting the video up. It was so uplifting, an just what we all need, music in our life. Thank you so very much. Peace be with you now, and always!
I tried having a guitar amplifier repair shop and I can see it could be profitable but my shop is so small, I couldn't get in to it for all the amplifiers. I could have been busy an easy 8-10 hours a day but I had no time for my own projects. A proper size shop and some good help could sure make some money and I think El Paso needs it. Cities like Austin or Denver would be a great place for a good repair shop.
@@ElPasoTubeAmps I agree. We did some limited Amp repair, and all guitar repair. Retail side drives business, though, and most folks want throw away stuff now. Couldn't make it work, but I am sure someone could. I may try again one day. 😂
Thanks for the tour of your station and equipment. You're right it's a lost art for sure. I love analog and tubes. I'm big into tube audio and I am a ham operator, AA5HL. At work I've been in radar at the FAA. I worked a 1957 ARSE-1E transmitter 100% tubes. Running magnetron oscillator/amplifier to a 5MW amplitron. The modulator was a hydrogen thyratron. I also work ASR-9 1MW klystrons, TDWR 300kW klystrons and surface radar 4kW TWT systems. I do solid state CARSR and ASR-11 but they are no fun. ASR-8 is a klystron radar as well that I work that is very unique. My ham equipment is Heathkit HW-16, Knight Star Roamer and Kenwood 599 Twins with 6146B finals. Audio equipment is KT88 Class AB PP with 6SN7 drivers from 1959. Also, EL34 Class A driven by 12AU7/12AY7/12AX7/12AT7. I'm still experimenting. Thanks again, I could listen to you all day.
Hi David, We are one in the same with our love for vacuum tube electronics. Your career is very interesting and that was what I wanted as a young man but computers became my career. I spent the first 26 years as a contract field engineer for NASA and WSMR and traveling around as needed to Sandia Labs, etc. all on mainframe computers - the last being a water cooled one at WSMR. I was never really interested in computers and I am still not but they were a good career and amazingly, still is. Of all the audio equipment I have accumulated, I listen to a homebrew Williamson using 7591 and those beautiful 1959 era 6SN7's you speak of and the OPT is a pair of UTC LS-57. I have built, and still have, the same thing with Acrosound transformers but I prefer the UTC as they seem to have a cleaner high end, to my ears. I like the EL34 also and always wondered why McIntosh never built with that tube. The last audio amplifier I built was a push-pull pair of 810 that would deliver 700 watts. That was taken to Denver by my friend who helped build it - just under a year ago. I still can't get enough of high-power RF amplifiers. I have said to others, am I like a painter that will only paint pictures of a vase with a single flower in it ? lol... Not exactly but I love RF amplifiers for some reason. I was given a 30S-1 recently. That is the amplifier to have, in my opinion. The old Collins stuff works and is repairable and has a wonderful receive and transmit quality to it. Please keep in touch. 73 WA4QGA
@@ElPasoTubeAmps sure thing. I'd like to keep in touch. I forgot to mention that I like CW and AM most in ham radio. I used to have a Johnson Viking Valiant and Collins R-390A some years ago. Yes, tubes are amazing. Right now I'm experimenting with these Chinese low power audio amplifiers and gutting them, modifying the circuitry with different coupling caps and components and seeing what comes of it. It's fun. My next adventure goes into a 300B or 2A3. I'll be talking to you. AA5HL Dave
When I was a young teen ham there was a gent who lived a could towns over who had a house full of Guitar amp projects and tube ham equipment. Used to love going over there to just nerd out on it all. Also I still have one of those Johnson Viking Messengers you showed, really cool piece of kit.
Ray, thank you for the tour of your shack, my silent key mentor indoctrinated me into the fold with prewar federal telegraph CW and AM transmitters. I particularly appreciate your home brew gear, I always had my operating position so I could watching the 866 flash when sending CW. 73
Very cool stash, you ever decide to have a garage sale I'll immediately jump on a plane for it! Funny how techies of our generation generally had similar interests. As a teenager I had a chemistry lab and made many rockets, some with the "caramel candy" propellant you mentioned and some from zinc/sulphur which was popular in the 60's. Always had an electronics lab and still prefer vac tubes to solid state. Made my first transmitter before I had a drivers license. Could only afford cheap telescopes as kid but now I have the same Meade you have. One question: did you ever try the water heater element load you made on RF? I have the 4 elements but never got around to making an enclosure for them (it's on the list...). I'm working on a 4) GU-81 amplifier and I'll need a large load for it. I always look forward to your videos; thanks for making them.
I never got around to using the zinc and sulfur rocket fuel although I have plenty of both of those ingredients right now. Maybe I will now that you have mentioned it. I got into black powder shooting some time back and make my own black powder. I get 3fg performance out of it. My BP is slightly lighter than the store-bought. I also got some KCLO3 and aluminum powder to spice it up a bit but realized that was probably going to turn out bad so I never mixed the two and tried it in my muzzle loaders... I did try the water heater elements for a 50 ohm RF load and it was not good. Obviously, too much reactance. I think it had some resonate points where it was close to 50+j0 but it was not a good thing. Recently, I heard about salt water RF dummy loads. Kind of made me want to build one. I think it would be fun to get the physical dimensions reasonably close to 50 ohms and maybe use a rod for the center post and let the outer part be a metal bucket be the other conductor, (gallon paint can - 5 gallon paint can ?? trash can ??) and make measurements. I suppose add salt to the water until it is about 50 ohms DC then start with some reactance measurements and see what the SWR or RL is. There are YT videos on it but I don't remember seeing anyone measure reactance or mention if the basic impedance changes with water temperature or evaporation. A lot of questions to be answered. Four, GU-81's that should put out a couple of watts and be beautiful. I hope you post it on YT so we can all enjoy it. 73 My video using the heater elements for a 50 ohm RF load. ua-cam.com/video/QE26rkAzWNc/v-deo.html
Some technical questions. 1. The transmitter valves are connected straight to the HT via the modulation transformer, with no other load? 2. Transmitter runs in class C, modulator in AB2? 3. What is the audio bandwidth? 4. What kinds of voltages and currents are flowing through all that thick cabling and switching to the antenna? 1. The transmitter valves are connected straight to the HT thru a RFC in the amplifier chassis (the resonate circuits are on the plate side of the RFC) with some bypass capacitors along the way on the HT side of the RFC and then straight to the mod transformer and the other side of the mod transformer secondary is connected strait to the HT. No other load. A class-C amplifier draws a steady load and its Z is simply its plate voltage divided by its plate current. Z = E/I 2. All plate modulated amplifiers run class-C. There must be enough negative fixed bias to control the plate current in the class-C amp to a safe quiescent level (with no RF drive) and then the rest (up to 2 or 3 times cut-off bias value) is made by use of a grid-leak resistor. This grid leak bias improves the linearity of the class-C amplifier. Low mu triodes work best for plate modulated, class-c amplifiers. Efficiency of a class-C amp is close to 80%. The reason it is so efficient is because of the high value of bias. The tube is conducting less than 180 degrees of each cycle so the tube is "off" more than it is "on" and this puts out a pulse rather than a sine wave. The other half (polarity) of the "sine wave" is reconstructed by the collapsing field in the resonate plate tank circuit. Pretty amazing. Class-C is only good for CW and FM and AM. No SSB stuff. 3. The modulator can be any class as long as you can provide audio at least 1/2 the power consumed by the class-C amplifier. Naturally, the modulation transformer has to provide a close match to make the modulator tubes happy on the primary and then make the class-C RF stage happy on the secondary side. Turns ratios of something like 1.6 are common and can usually be made to work with most amplifiers of the power level of the mod transformer. A 1000 watt class-C tube needs at least 500 watts to modulate it 100%. The modulator doubles the peak voltage (for 100% positive modulation) and makes it go to zero for 100% negative modulation. You never ever want to actually go to a peak voltage of zero because the amplifier stops putting out RF power and the transmitter turns off - even for microseconds and all hell is created in sidebands when it turns back on as the plate voltage rises above the peak zero level. That is why you must control the negative modulation level but you can put as much positive modulation on as you want until you melt the tubes... 4. The RF voltages on the 50 ohm coax are surprisingly low. Plain old ohms law again. V = sqrt(P * R) so for 1000 watts the voltage is 223.6 volts of RF into 50 ohms, which almost all antenna systems are 50 ohms. On the other hand, the voltages are in the thousands on the plate side of the resonate plate tank circuit. Amazing how it works and transforms impedance from say, 4000 ohms to 50 ohms. Think of the voltage on the plate side of that tank circuit - for 1000 watts it would be 2000 volts of RF. Arcing can easily occur at that RF voltage level. That is why all the ceramic band switches are located on the low-Z side of the tank circuit. You actually short-out the turns you don't want. That is the way it is done with a switching network or a roller inductor. Some have said, wouldn't that cause a voltage across the shorted turns? Apparently not. Again, that is the way it is done. 3A. I forgot to mention but you don't want to take up more bandwidth than necessary to sound good, 3.5 KHz is acceptable and limit the lows, as there is a lot of wasted power in LF and voice actually becomes harder to understand when bassy. Some guys run high-end mics and if the conditions are really good, it is nice but just a little QRM (noise, etc.) makes it harder to understand.
Commercial AM stations run the DC to the class-C amplifier thru a large choke (reactor) and put the audio across it thru a capacitor to keep all DC off the modulation transformer so as to keep from biasing the core of the transformer and limiting its LF response by lowering the inductance because of the DC bias. Every ham radio modulation transformer I know of is built so DC can be run thru the secondary and not bias the core excessively. Once when I tried making a SE 833A I used a push-pull transformer and frequency response below about 80 Hz was seriously distorted - still perfectly good for voice but a PP transformer is not made for DC thru any of its windings except, of course, the primary where it is in opposite directions to the plates of the tubes and does not bias the core. The first and one of the cheapest form of modulation was to load the plate of the modulator tube across a choke. This is usually a SE modulation stage and low power. You can also modulate the screen of the final amplifier or even previous stages providing RF to the input of the final amplifier but then class-C may have to be changed to something more linear. These are the cheap ways to get an AM signal on the air but not very efficient or effective. You end up with weak audio and may never be able to reach 100% modulation. Takes a lot of "iron" to make a powerful AM station. Search for, "Gates BC-1J 1000 Watt AM Transmitter" if you want to see a classic AM transmitter schematic.
@@fjs1111 I couldn't think of that word "Geiger counter" while making the video. The challenges of an ageing brain. My grandson and I, and others, have made a few trips to Trinity site and made videos of it - lots of people have - but we made measurements and can see that it is about 10X more radioactive there than in, for example, El Paso. That is still not really alarming but it can be measured with simple devices like the vintage CD (Civil Defense) Geiger Counters. I had a "nuclear stress test" a few years back and the Geiger counters can detect me at a distance of 20 feet or so. You are seriously radioactive for a while after the procedure. My wife had a PET-CT recently and the same was true for her but her radioactive level was gone in one day whereas mine was detectable three days later.
@@ElPasoTubeAmps You got quite a collection of tubes. Really enjoyed the videos. The mercury vapor rectifiers are awesome too. They need a very high voltage though right? I've seen videos on youtube of some large mercury arc rectifiers for powering subways and they are something awesome to watch!
@@fjs1111 MV rectifiers don't need to operate at high voltage and can be used just like a 5U4. The voltage drop is constant and about 15 volts unlike a high-vacuum rectifier where the voltage drop increases with increasing plate current. A pair of "little" 866A rectifiers can power a transmitter at 1500 watts or more. I can see them almost as the solid-state rectifier equivalent of 100 years ago. I have watched those videos of rectifiers for subways also. They are beautiful and somewhat terrifying. I would keep my hands in my pocket around them... anything that has thin wire with lots of insulation and sizzles when it is on should be treated as deadly...
@@ElPasoTubeAmps I had missed the part about the Nuclear stress test, wow I never gave much thought to that but for the machines to detect it you must be a fairly powerful emitter! Thanks for the mercury arc info, I was thinking more I guess of the high voltage one's that look like a octapus. Look forward to your videos to come!
Great video Dave. The only part you didn’t cover was the rf exciter ? Where does the rf frequency drive get into the mix? Was it the Collins transmitter on CW? GOD BLESS
Yes, it is the Collins transmitter on CW that provides the carrier frequency. A couple of issues using it - although it works "great" it is from 1947 and does drift slightly. Not enough to be noticed by anyone listening on AM but often times others listen to only one side band as if it were a SSB signal and in that case, the drift causes the carrier to appear and people get annoyed by that - I can understand - also it is 15 watts (actually about 18 watts) which is plenty to drive the Millen amplifier but sometimes too low for other amplifiers. I have an old iCom (circa 1995) that I basically use for a VFO (it has an audio problem) and it puts out around 75-80 watts of carrier and has a stable VFO. I have built a 4-1000A amplifier, grounded grid, that I keep on 40M and drive with a new iCom 7300. Took some getting used to the software defined configuration but I finally got there. The iCom 7300 is a nice radio. I can understand why there are so many out there. Thanks for your comments. I have some ideas for more videos - just got to go to the shop and get busy. 73
David, do the cats have their own call signs? And are they on 20m or 40m? Bet you find the controls all over the place in the morning from where you left them the previous night. Do they change coils on you? Keep well. EJP
I haven't gotten them on the air yet but I do have their names in my passwords. The two that have been in videos for years have passed away - both were 14. A new beautiful cat has taken up with me. They find me, I never find them. This one I call, Pretty Boy, and is a full blown Tom-cat. Very affectionate but has to go out every other night and be with the gang... got him fully vaccinated and microchipped. I think I am ready for the microchip so I can just walk into stores and get what I want and they send me the bill.
@@EJP286CRSKW I sometimes wonder if my new tom cat, Pretty Boy, is two-timing me. Living with me for a couple of days and then living with someone else. He is beautiful cat. When he wants treats, he just walks up to the cabinet doors, stands on his hind legs and opens both doors at once by grasping the doors at the top. Where did he learn that? I wish I was as young and strong as he is - I may have been a long time ago... :-) As a kid I remember old people talking of the, Fountain of Youth. I thought, at that time, what is their problem ? why don't they just grow up and act their age. I understand now... Remember me saying cats choose me ? maybe I smell like chicken. The last dog I had was when I was 16. A wonderful female English Setter. We are doing OK right now.
🙂 As you mentioned the RF amplifier being on top and the modulator in the middle, I had immediately thought of a Linear amplifier. Is the a way to add the secondary of the modulation transformer from the modulator to a Linear amplifier? I want to believe there is a way but I do not have the full understanding, so maybe not ??? Great Video with great explanation, Thank you.
I should had mentioned as well also adding just a transmitter in general with out its original modulator. In other words using the Linear as the final of the transmitter of sorts. I understand you have to have an frequency oscillator along with a crystal or use an VFO/DDS in order to create a Carrier.
Love the shack Ray! I run A BC-610E Still :) But I didn't have it last time we spoke on 20m though. I hope to find ya again sometime . 40M has been good for AM lately. What tube could be a good substitute for the 250th if I ever needed to do a retrofit my BC-610 using the stock iron? 73
Hi Tom, A substitute for a 250TH - Wow... I have never built with those tubes although I think they are beautiful. A 250TH is considered a high mu triode (mu = 37) back in its day. 5V, 10.5 amp filament. I can't think of any tube like that with that four pin base, etc. I still see them on Ebay usually for a reasonable price. I can tell you that the 4-125A is a good substitute for 810 tubes as far as performance and specs go but a lot of hardware changes would be necessary. I bought four 304TL tubes a couple of years ago that were a beautiful quad and by the time I got them, three of them had the filaments broken out. I am convinced they were good when sold, and the seller gave me all my money back, but I bet they were destroyed in shipment. Same thing has happened to some 813's I have purchased. Filament busted when I get them, and again, get a refund but I feel like shipping these vintage tubes is likely to be the end of them so that is a big problem. Maybe finding one at a hamfest is a better idea? I have had at least one BC-610 in my life, maybe two, but I know I parted them out and have no idea where all the parts went. That was decades ago. I do run what I think is a BC-610 modulation transformer in one of my AM rigs and use a pair of 4-125A into the transformer to modulate push-pull 812A in a James Millen amplifier. Gave me exactly the right impedance ratio but the modulation transformer I have is a UTC and is round and potted but it has the Z ratio of the BC-610 transformer. Anyway, hope to hear you on. I hang around on 40M and 20M and run a homebrew 4-1000A driven by a 7300 on 40M and keep my Collins stuff on 20M. 73 WA4QGA
@@ElPasoTubeAmps Thanks for the info! Much appreciated. If the time ever comes I'll probably have to change out the socket to except a different tube altogether and may not be worth the effort. But I'll buy a 250th when I get the opportunity to possibly avoid the hole process . The old girl is running good at the moment. 73 Ray I'll be looking for ya on 40m in the afternoon!
Hello, Question, if your rf amplifier has 1250vdc and your modulator is providing 2000vac when you provide 100 percent modulation, you'll have 3250 positive but when your 100% negative, does that not take you below zero as 1250 minus 2000 is minus 750 plus your keep alive and you would still be negative 1150 with your keep alive at 100 volts. I know you said 75 but thats even worse according to your explanation. If I totally misunderstood your explanation please forgive me. Can you elaborate on this as it does not add up according to my interpretation of your explanation which made sense until I thought about your actual voltages. Thanks and great video and I plan on building an am station with a modulation deck . Keep it going, love your content!
I understand your question although I have never thought about it that way. You have the voltages correct for RF amplifier and modulator as they are separate power supplies. The positive peaks are around 120% and can peak up a little more and the negative peaks would, as you mention go to zero and shut the RF amplifier off and do all those terrible things called "splatter". If you overmodulate in the negative direction grossly, it just keeps the carrier shut off for longer if you don't have any kind of negative modulation control. It doesn't go negative in the way you explained it but maybe it would without this circuit. I have never heard it thought of that way and what you say seems to make sense but for reasons I cannot explain it doesn't work that way. Or maybe that is why the carrier is shut off for longer periods of time - i.e. longer gaps between the sine wave assuming we are modulating with a sine wave. Again, I have seen this so this is why I am trying to explain it this way and, as mentioned, the carrier would just be at zero for a longer period of time without the control circuit and your analysis would be correct - I think.... The seemingly insignificant 75 volts doesn't seem like it would work but it does. No matter how negative the peaks go on the modulation envelope, 75 volts remains to the plate of the class-C final and keeps it from totally shutting the carrier off. I don't know why or how to explain why we don't get the algebraic sum of these two voltages and it end up negative but it doesn't. Maybe I do, actually..... lets try... I don't have the schematic in front of me at the moment but I bet if we examine it closely one of the diodes probably ends up reversed biased and won't let current flow past the zero point. Seems like there is a capacitor there that shunts the modulating signal to ground - I am grasping as straws without the schematic. I have even read that some guys have controlled negative peaks with as little as a 9V battery. I cannot confirm this and surely it would be on a very low power transmitter. I can't do it now because it is 4:15 AM and I need to get to bed. 🙂 but I bet it is something like I was rambling on about above. 73 better go for now...
Thank you! Can you share the schematic with us as I now have AM fever and I'm going all in/ out! Your explanation makes sense but I do have a few more questions. Also, I am building a clone of the 30k1 and ild like to see if you could do a video or a chasis for 2- 3-1000s ? This is one of the decks I plan on building and another deck with 3 x 3-500z or 3 x 4-400s in a triangle I think the 2- 4-400s look great but scoot them back a couple inches and put another one in the middle towards the front and peoples heads would spin off. Nothing like 3 tube amps. In fact, I've been looking for a LK-550 and they are unobtainable. Amp supply co used 3 x 3-500zed in that amp and I've never seen one for sale. Thanks for your help and great content
@@jaredmahan4090 Check out QRZ page for K0JJF as he built a three tube amplifier as you describe. I don't have a schematic of the transmitter other than the James Millen schematic that can be found on the Internet. A pair of 3-1000Z would be quite the project. You know each tube needs 7.5V at 21A. It would be difficult to fit it in the 30K1 cabinet. My favorite tube has always been the huge 833A. I love that amplifier. It has real balls... 73
Ever since I read your comment, I realize I need to make those measurements. I will get back with you soon. I am going to guess about 1 KW. Years ago when I built my 4CX1000A and at its max rated carrier output power of 1680 watts, the input was right at 3 KW. That is 56% efficiency. I figure AM is a little less efficient than that.
Every ounce of the equipment came down those stairs with the exception of the Collins 30K-1 which was brought in thru the basement door where the big fan is. That was not really a great idea as I look back on it. That happened in 1993 when I bought this old house. Myself and a friend brought it down the outside basement stairs and I was only 43 years old and a lot stronger. Like to have killed both of us and I am sure I removed the internal components. That steel cabinet Collins made back in 1947 must have gained weight over the years... When we did get it to the basement I remember looking at my fiend and we were both happy to be alive and I remember saying that I will never try to take it out of the basement. There is also a safe in the basement that I had a couple of whimps help me with and it almost got away coming down the steps and would have squished me had it gotten completely away. I think it was 400 pounds. A friend and I, just a few months back brought the Collins 30S-1 down the stairs but it is only 180 pounds so that was not too difficult.
Fan is there to keep the litter box cooled. And don't let the group on 3840 hear you say that antenna tuners are a good thing. It's a Resonant dipole on coax cut for 3840, nothing else will get out.
I don't have enough room for any type of 80 meter antenna except for the Isotron I put up a few months back. Not too sure about that Isotron... very narrow bandwidth and I have never made a contact with it - I have to admit, I have not tried very hard. In the early 70's I ran a homebrew KW AM station on 80M in Huntsville, AL. I loved the guys I made friends with back then. Ran a single class-C, 4-400A and plate modulated it with a pair of 4-400A. Not sure if I will ever go there again. I have listened to some of the guys on 80M and some sound pretty good but some are over modulated and splatter. Those are the ones I was thinking of when I made some comment about splatter. I used to be hard-nosed against antenna tuners also but that is not warranted. They certainly can make the transmitter happy and that is not a bad thing... As far as helping a signal radiate or receive, I am still not totally sure but I don't think it hurts in any way.
I am very sorry to hear about your father. Sometimes live gets hard. My beautiful wife of 45 years died on June 19 of pancreatic cancer. We didn't even know there was anything serious wrong until the end of February. It only took four months. I took her to the best hospitals, MD Anderson in Houston. She passed here at home and in out bed with my son and me with her. It's tough sometimes for sure. I have wonderful friends around and some of them played music for Marilu just before the end and I posted the video. Comments are disabled and I really can't watch it much but the music is beautiful. Stay busy, not insane busy running around like a mad man, but it's just not our turn yet. We all have to go there and I completely believe we will be back with all our loved ones when we pass from this life on Earth. Life here is certainly temporary. I hope your father passed peacefully and I am sure he is doing just fine now but we sure miss our loved ones. 73
Thank you so much I did watch the last video it was beautiful I’m so sorry I’m happy you are moving forward and showing and teaching us about electronics I find them like treasure and have the same energy as you i just lack the major knowledge I know how to assemble but not engineer I find it takes so much time that I don’t have My dad left me his work bench with every tool known to man and hardware mostly from USN
@@jimcatanzaro7808 Your dad's workbench is his and you can make it yours with his influence. Just because our loved ones are out of this realm of life does not mean they are not with us. It is a slow and painful process to move forward but it is up to us to do it. No human or spirit can do it for us. I see my wife as a daily influence in my as you must see your dad's influence. There are no instant and painless answers but you are blessed and given the energy to move on. It would be much easier for me to just give up and die. Seems like the easy way out but with all love and respect, find the value in your loved ones and friends and allow them to help you. I don't mean become dependent on them but receive the energy they can give you while they can that you can build on. That is what is working for me.
Aren't modulation transformers more or less unobtanium these days? Unless you happen across something at a hamfest but then what are the odds of it being exactly what is needed for a given project?
Modulation transformers could be considered unobtanium except for those that won't give up... they can be hard to find but continuous looking and luck is how they are found. This transmitter uses a modulation transformer from a WWII, BC-610 which ran 100TH modulating a 250TH. It is AM so the 250TH is running class-C and you can figure the load impedance of the 250TH by simple R = E/I - the plate current is essentially constant for a class-C amplifier varying little under modulation. If you can't find everything in the BC-610 manual (and you probably can't) you go to the Eimac data sheets and see it wants 2000V @ 250mA so we have R = about 8K - that is close enough. Then to the Eimac datasheet for the 100TH and you see it wants 15K for 2000V for a class-B modulator. So now you have a pretty good idea of the turns and Z ratio of that transformer. Z ratio is around 1.88. I don't think that is perfect but it is close and gives something to start with. If you have an impedance meter, you can start doing a series of measurements with different loads and figure the Z ratio out exactly - or you can just do the turns/voltage ratio measuring voltage into one set of turns and out of the other set of turns (carefully... with low voltage so as not to electrocute anyone...). Now you know your modulation transformer. Then you find or figure out the load your class-C amplifier that you are going to build needs and start selecting a set of push-pull modulator tubes to match the other side (the primary side) of the modulation transformer. In my case, I found that a pair of 4-125A running (I think AB2) needed exactly the Z presented by the transformer so that the secondary Z to modulate the James Millen amplifier running push-pull 812A was practically a perfect match. I think careful measurements revealed this BC-610 transformer was a turns ratio of something like 1:1.6 if I remember correctly which would be a Z ratio of 1:2.56 which would make a 8K load reflect back to the modulator tubes as about 20K. Eimac datasheets will tell you what the tube will actually do if you give it the voltages they specify. My AM transmitter in this video is slightly more complicated than some as I use separate power supplies for the modulator and class-C RF amplifier. I run 2KV on the modulator tubes and 1250V on the RF amplifier. I don't think you ask for all of this but it is a thought and action process on figuring out how to use a modulation transformer to make it work with a number of different tubes. In many cases this range of turns/impedance ratio is close in to what I have shown in many modulation transformers and the matching does not have to be perfect. Lastly, most all amateur radio transformers are designed to have the class-C plate current pass thru the secondary of the transformer and not saturate the core. If you look at commercial AM transmitters, they use a huge choke and apply the modulation across that choke and separate it with a capacitor so no current flows thru the secondary of the modulation transformer so as to improve the HiFI quality of the signal for commercial broadcast purposes. It is rare to find high level modulation transformers and I have the Mother of them all - an 85 pound multi-tap UTC transformer that I hope to use some day. For now, it is going to be hard to beat the 300 watts of carrier, fully modulated, that I get from the James Millen amplifier running push-pull 812A tubes. Hope this helps.
@@ElPasoTubeAmps It does help and thanks for the walk through. So... it seems I should keep an eye out for whatever interesting transformers that might come my way and then find a compatible project to use it. My thought previously was to pick a project and then try to track down the parts and it just hadn't occurred to me to use an available transformer as the focal point for a project. Anyway, thanks for the reply and perspective.
@@MikeBenedict1 Huge projects have started for me from a single hard to get item. I was given several new 4CX1000A around 1982 that spawned 40 years of amplifier building. My wife and I found a beautiful turquoise oven for $50 that built a $10,000 pergola... lol.... I can stare at one single item and build a world or projects around it. Keep building. This seller often times has a good transformer selection. www.ebay.com/str/audiopathicdistractions?_trkparms=folent%3Aaudiopathicdistractions%7Cfolenttp%3A1&_trksid=p3542580.m47492.l74602
If I were building a new AM transmitter, I'd use a Class-D PDM modulator, which doesn't employ a transformer. In that scheme, the modulator performs as a switching regulator. The audio is converted into pulses of varying width, by a ramp generator & comparator. This is amplified and applied to the grid of the modulator tube, which is in series with the P.A. plate. The modulator turns on and off, which provides much higher efficiency, than it would if it were linear. The P.A. plate L-C circuit provides the integrating action, which converts the pulses into audio. A diode stack suppresses the inductive kick-back (like the damper diode in a TV fly-back). This modulation method provides much better efficiency than a regular high-level linear modulator. The only disadvantage is that the P.A. requires a much higher B+, because there is no voltage step-up from a modulation transformer. In the 1980s, I was in charge of the "care and feeding" of a 50 kW Harris MW-50A AM transmitter, which worked this way. The modulator tube was a 4CX5000, the P.A, a 4CX35000, and it employed a 24 kV P.S.
@@Pootycat8359 I don't know why but I have always had a fascination with high power transmitters. Your Harris transmitter is certainly impressive. I still have a pipe-dream of coming across a vintage Gates with 833A or Collins with 4-400A and putting it on the air but it may not come true and that is OK. Honestly, I have been very impressed how well 300 watts (carrier) of AM compares to SSB of 1500 watts. The 1500 PEP watts of SSB does "outperform" it in its own way but everyone seems very pleased and comments on the quality of a good AM signal and even seem surprised by its S-meter strength. Thanks for your information. I find it very interesting,
Hello im midway through a build of a similar setup. My problem is finding a appropriate modulation transformer that can handle 2-5 hundred watts or more. Any ideas??
The modulation transformer is the biggest challenge. It is also important to get the impedance of the modulator and the class-C amplifier correct. What are you using for modulator tubes and what RF tube are you going to use? I may be able to help but I need to know the voltage and current of the class-C amplifier and the same for the modulator. I have found what I want more than I ever imagined but it took years of looking. Get acquainted with other AM groups. They may be able to help. Check out this seller. Sometimes he has modulation transformers and I buy a lot from him. 73 www.ebay.com/str/audiopathicdistractions? _trkparms=folent%3Aaudiopathicdistractions%7Cfolenttp%3A1&_trksid=p3542580.m47492.l74602
This is the ultimate multimatch transformer. 600 watts. I have one of these and use it with a pair of 3-400Z to plate modulate a GG 3-400Z running class-C. www.ebay.com/itm/196223041404?itmmeta=01HW718DKF7JSSJRH635D7GSEY&hash=item2dafcdff7c:g:GM4AAOSw1xBlvKqb&itmprp=enc%3AAQAJAAAA8BCwNJyeqWbLkG50v12T7oPwewoqLtWE%2FBSkD1KK0nGXR0w8Dybb7naWaNQQTRPD5jnUI1j9K84hR8qgsxL9wG3jJWQOPQlZUM5uuTOHR%2BEHO110yTG2vutR%2BxcV0c3gaRDqj9sAL1yaZwKrQCYNQ01JVtgvSnZuN%2B6TJ4TWBZdS89qoyOx2f%2FC6jV62Mn9zMnUJbp%2BPe2RfcBd1M0twiCosg2t%2FFqdyezKPKt3sTzpCPR7QY0SGfhHa2OW0%2BuB4Q5Hrh%2FFRmcBUTprTrkCTWy36a3NEVYDUhlesdsY%2BfEsvnYvTT32Pr0%2BrMlFZ%2F7EMcg%3D%3D%7Ctkp%3ABk9SR_jZoeHhYw
Besides power level, it is all about the impedance values you need for the modulator and the class-C stage. www.ebay.com/itm/116083109330?itmmeta=01HW718DKF5SJABNZYRHNBRQR9&hash=item1b0717add2:g:UXIAAOSwNWll3ibP&itmprp=enc%3AAQAJAAAA8NVTjVDoQXMlNqtskrdDHo5zTGMZ--JUr3HnV8WPB%2FrJnst3L1f0%2F06o4ZUUP42ismzn7yI7O3P5Q7dt%2Ff429q3oD338Gt%2BsFt%2BWzPKv%2BxfP8%2FUR8H922s3W2W8UYTbT4CVXSsAysZrxe0RL6uE2r4U066X21YMPDW4eRFdgIXrKxfl%2BHCplYbEH%2Bfnd4dynpdTYAnB%2BebnVaOH1CBgnd3pYqVp2ABBgznrm3iSCax7PjEuAuASPKYyChoacTFIWZ%2Fna278JIYMxcPdachSzbU3xd5S0clYBEQbbHR22wpMKbbfPQ6TUNcgJ8RU09AYCzQ%3D%3D%7Ctkp%3ABk9SR_bZoeHhYw
@ELPASOTUBEAMPS I'd like to find a duplicate modulation tranny as you have with multi tap primary for the options. I've been searching everywhere for one of those. (Please help) Depending on iron available, I plan on using a pair of 4-400s modulating a pair of 4-1000s/8166 or something similar. I know it's overkill but I like two big glass tubes vs 1 tube.
I have the dream-come-true modulation transformer I am willing to sell. It weighs 85 pounds and is the UTC VM-5, 600 watts. I know it works as I have used it with a pair of 3-400Z to plate modulate a 3-400Z, grounded grid, class-C for AM. I did have to mount it in a large ammo box as it "talks" a bit loud under modulation but it will match anything. Here is one on Ebay so you know what it looks like. www.ebay.com/itm/196223041404 Here is its spec sheet. amfone.net/Tech/UTC/UTC.pdf You will have to come get it - I can not pack and ship it. I will take $250.
The number of things you showed made my day. Hope you good health and long life fella. Keep the videos coming too. vf
As we get old, some of us want to give away what we have experienced and tend to pontificate. We know the trip is getting close to the end and the train is slowing down and we have to get off in Paris - or some place with a name similar to that. Is there ham radio equipment in Paris? Seriously... thank you - I enjoy making these seat-of-the-pants videos and hope they are of some value to all of you.
May God give you many many more years to go ❤️❤️❤️🔥 my respect and i cud sit 🪑 on your class room for ever you remind me of my v.e back in the early 90s if you been a v.e they most to love you ....the way you have to teach is a gift from above sir ...i take my hat 🤠 off 73 ...
A trip to memory lane. In the late 1950s and early 60s I was pretty much involved with Ham radio. I always built my own transmitter and receiver but things changed in my life and I went to different path.
In the 1980s I had a handheld transceiver, Icon or Yaesu, don't remember and one day I got home late from work and left it on the seat of my car and some passer by stole it.
Since then I never went back to Ham radios. I even forgot my call.
We are on an up-cycle of the 2020 to 2031 sunspot cycle so now might be a good time to enjoy ham radio again. I don't care one bit if I make DX contacts but many people do. I have been at it pretty consistently since 1963, with a little slow-down here and there, but building in my passion and it helps keep me sane. 73
@@ElPasoTubeAmps Thank you for your reply.
Very few people pay attention to the solar cycles. As you may know we are on the way to solar maximum (solar cycle 25) peaking sometime in 2024 or 2025.
Maybe I could get an used Yaesu and get involved again.
Tamitha Skov always talks about solar flux affecting ham radio propagation. Tamitha Skov is the space weather woman, check her out on UA-cam if you don't already follow her.
I am really glad to see a new video from you. You are a really good guy. It is nice of you to share your experience and knowledge here.
agreed!
Hi David, Thanks for the tour of your AM and other gear. You really have some neat equipment. I have always been more interested in CW but from time to time I listen to the AM guys and enjoy their QSO's. I am still restoring R390, 390A, 391 and 392 receivers as a retirement FUN job after years with DEC Digital Equipment Corp. The only issue is my back is shot and the docs want to fuse L4, L5 and S1. I guess I need to stop and get it done while I am still young enough, I hope, to recover. Age 66 now.
agn tnx fer nfo es 73 de WA4AOS dit dit
You have some beautiful equipment! AND it ALL WORKS!
Thanks for the tour.
I love your AM gear, I only have cheap 27Mhz CB but it's the same. Good health to you. These old devices are great, I respect them a lot, it shouldn't be retired. good quality housings, good microphones, beautiful indicators, analog scales and bulbs are all amazing. I've always wanted a small tube or transistor radio station in old-fashioned housing. You can see it in some old movies, it was very mysterious, only for a select few. Health again :-)
Id give my left arm to sit and chat with you, your much like my late Father who was an ametuer extra class, also a radar engineer for Lockheed Aircraft Service back in 1954/78. Dad had alot of homebrew equipment but not to the level that you have, He also was a big 20m fan as well.
Thank you for your tour!.
👍🏻 I'm leaving a quick comment here because the "Marilu" video has comments disabled.
I just wanted to say how much I enjoyed the beautiful music and a quick glimpse at your very loving family.
That's pretty rare in today's world.
You have an outstanding channel and have educated my 57 yr. old solid-state brain about the fascinating world of vacuum tubes. You are a true wealth of knowledge!
So... Thank You!!
🎙️
73 from KD2MKZ
a Current Captive of the PRNJ
("People's Republic of New Jersey) 😁
I realize why you had the comets off in your latest video. I just wouldn’t to thank your from the bottom of my heart for putting the video up. It was so uplifting, an just what we all need, music in our life. Thank you so very much. Peace be with you now, and always!
Had a guitar shop in El Paso at one point, sure wish we'd have met! Awesome stuff! Thank you! -Frank (KI5JAD)
I tried having a guitar amplifier repair shop and I can see it could be profitable but my shop is so small, I couldn't get in to it for all the amplifiers. I could have been busy an easy 8-10 hours a day but I had no time for my own projects. A proper size shop and some good help could sure make some money and I think El Paso needs it. Cities like Austin or Denver would be a great place for a good repair shop.
@@ElPasoTubeAmps I agree. We did some limited Amp repair, and all guitar repair. Retail side drives business, though, and most folks want throw away stuff now. Couldn't make it work, but I am sure someone could. I may try again one day. 😂
Thanks for the tour of your station and equipment. You're right it's a lost art for sure. I love analog and tubes. I'm big into tube audio and I am a ham operator, AA5HL.
At work I've been in radar at the FAA. I worked a 1957 ARSE-1E transmitter 100% tubes. Running magnetron oscillator/amplifier to a 5MW amplitron. The modulator was a hydrogen thyratron. I also work ASR-9 1MW klystrons, TDWR 300kW klystrons and surface radar 4kW TWT systems.
I do solid state CARSR and ASR-11 but they are no fun.
ASR-8 is a klystron radar as well that I work that is very unique.
My ham equipment is Heathkit HW-16, Knight Star Roamer and Kenwood 599 Twins with 6146B finals.
Audio equipment is KT88 Class AB PP with 6SN7 drivers from 1959.
Also, EL34 Class A driven by 12AU7/12AY7/12AX7/12AT7. I'm still experimenting.
Thanks again, I could listen to you all day.
Hi David,
We are one in the same with our love for vacuum tube electronics.
Your career is very interesting and that was what I wanted as a young man but computers became my career. I spent the first 26 years as a contract field engineer for NASA and WSMR and traveling around as needed to Sandia Labs, etc. all on mainframe computers - the last being a water cooled one at WSMR. I was never really interested in computers and I am still not but they were a good career and amazingly, still is.
Of all the audio equipment I have accumulated, I listen to a homebrew Williamson using 7591 and those beautiful 1959 era 6SN7's you speak of and the OPT is a pair of UTC LS-57. I have built, and still have, the same thing with Acrosound transformers but I prefer the UTC as they seem to have a cleaner high end, to my ears.
I like the EL34 also and always wondered why McIntosh never built with that tube.
The last audio amplifier I built was a push-pull pair of 810 that would deliver 700 watts. That was taken to Denver by my friend who helped build it - just under a year ago.
I still can't get enough of high-power RF amplifiers. I have said to others, am I like a painter that will only paint pictures of a vase with a single flower in it ? lol... Not exactly but I love RF amplifiers for some reason. I was given a 30S-1 recently. That is the amplifier to have, in my opinion. The old Collins stuff works and is repairable and has a wonderful receive and transmit quality to it. Please keep in touch. 73 WA4QGA
@@ElPasoTubeAmps sure thing. I'd like to keep in touch. I forgot to mention that I like CW and AM most in ham radio. I used to have a Johnson Viking Valiant and Collins R-390A some years ago. Yes, tubes are amazing. Right now I'm experimenting with these Chinese low power audio amplifiers and gutting them, modifying the circuitry with different coupling caps and components and seeing what comes of it. It's fun.
My next adventure goes into a 300B or 2A3.
I'll be talking to you.
AA5HL
Dave
A wonderful trip down memory lane. Thanks👍
When I was a young teen ham there was a gent who lived a could towns over who had a house full of Guitar amp projects and tube ham equipment. Used to love going over there to just nerd out on it all. Also I still have one of those Johnson Viking Messengers you showed, really cool piece of kit.
Ray, thank you for the tour of your shack, my silent key mentor indoctrinated me into the fold with prewar federal telegraph CW and AM transmitters. I particularly appreciate your home brew gear, I always had my operating position so I could watching the 866 flash when sending CW. 73
I love your videos they make my day
Very cool stash, you ever decide to have a garage sale I'll immediately jump on a plane for it!
Funny how techies of our generation generally had similar interests. As a teenager I had a chemistry lab and made many rockets, some with the "caramel candy" propellant you mentioned and some from zinc/sulphur which was popular in the 60's. Always had an electronics lab and still prefer vac tubes to solid state. Made my first transmitter before I had a drivers license. Could only afford cheap telescopes as kid but now I have the same Meade you have.
One question: did you ever try the water heater element load you made on RF? I have the 4 elements but never got around to making an enclosure for them (it's on the list...). I'm working on a 4) GU-81 amplifier and I'll need a large load for it.
I always look forward to your videos; thanks for making them.
I never got around to using the zinc and sulfur rocket fuel although I have plenty of both of those ingredients right now. Maybe I will now that you have mentioned it.
I got into black powder shooting some time back and make my own black powder. I get 3fg performance out of it. My BP is slightly lighter than the store-bought. I also got some KCLO3 and aluminum powder to spice it up a bit but realized that was probably going to turn out bad so I never mixed the two and tried it in my muzzle loaders...
I did try the water heater elements for a 50 ohm RF load and it was not good. Obviously, too much reactance. I think it had some resonate points where it was close to 50+j0 but it was not a good thing. Recently, I heard about salt water RF dummy loads. Kind of made me want to build one. I think it would be fun to get the physical dimensions reasonably close to 50 ohms and maybe use a rod for the center post and let the outer part be a metal bucket be the other conductor, (gallon paint can - 5 gallon paint can ?? trash can ??) and make measurements. I suppose add salt to the water until it is about 50 ohms DC then start with some reactance measurements and see what the SWR or RL is. There are YT videos on it but I don't remember seeing anyone measure reactance or mention if the basic impedance changes with water temperature or evaporation. A lot of questions to be answered.
Four, GU-81's that should put out a couple of watts and be beautiful. I hope you post it on YT so we can all enjoy it. 73
My video using the heater elements for a 50 ohm RF load. ua-cam.com/video/QE26rkAzWNc/v-deo.html
Some technical questions.
1. The transmitter valves are connected straight to the HT via the modulation transformer, with no other load?
2. Transmitter runs in class C, modulator in AB2?
3. What is the audio bandwidth?
4. What kinds of voltages and currents are flowing through all that thick cabling and switching to the antenna?
1. The transmitter valves are connected straight to the HT thru a RFC in the amplifier chassis (the resonate circuits are on the plate side of the RFC) with some bypass capacitors along the way on the HT side of the RFC and then straight to the mod transformer and the other side of the mod transformer secondary is connected strait to the HT. No other load. A class-C amplifier draws a steady load and its Z is simply its plate voltage divided by its plate current. Z = E/I
2. All plate modulated amplifiers run class-C. There must be enough negative fixed bias to control the plate current in the class-C amp to a safe quiescent level (with no RF drive) and then the rest (up to 2 or 3 times cut-off bias value) is made by use of a grid-leak resistor. This grid leak bias improves the linearity of the class-C amplifier. Low mu triodes work best for plate modulated, class-c amplifiers. Efficiency of a class-C amp is close to 80%. The reason it is so efficient is because of the high value of bias. The tube is conducting less than 180 degrees of each cycle so the tube is "off" more than it is "on" and this puts out a pulse rather than a sine wave. The other half (polarity) of the "sine wave" is reconstructed by the collapsing field in the resonate plate tank circuit. Pretty amazing. Class-C is only good for CW and FM and AM. No SSB stuff.
3. The modulator can be any class as long as you can provide audio at least 1/2 the power consumed by the class-C amplifier. Naturally, the modulation transformer has to provide a close match to make the modulator tubes happy on the primary and then make the class-C RF stage happy on the secondary side. Turns ratios of something like 1.6 are common and can usually be made to work with most amplifiers of the power level of the mod transformer. A 1000 watt class-C tube needs at least 500 watts to modulate it 100%. The modulator doubles the peak voltage (for 100% positive modulation) and makes it go to zero for 100% negative modulation. You never ever want to actually go to a peak voltage of zero because the amplifier stops putting out RF power and the transmitter turns off - even for microseconds and all hell is created in sidebands when it turns back on as the plate voltage rises above the peak zero level. That is why you must control the negative modulation level but you can put as much positive modulation on as you want until you melt the tubes...
4. The RF voltages on the 50 ohm coax are surprisingly low. Plain old ohms law again. V = sqrt(P * R) so for 1000 watts the voltage is 223.6 volts of RF into 50 ohms, which almost all antenna systems are 50 ohms. On the other hand, the voltages are in the thousands on the plate side of the resonate plate tank circuit. Amazing how it works and transforms impedance from say, 4000 ohms to 50 ohms. Think of the voltage on the plate side of that tank circuit - for 1000 watts it would be 2000 volts of RF. Arcing can easily occur at that RF voltage level. That is why all the ceramic band switches are located on the low-Z side of the tank circuit. You actually short-out the turns you don't want. That is the way it is done with a switching network or a roller inductor. Some have said, wouldn't that cause a voltage across the shorted turns? Apparently not. Again, that is the way it is done.
3A. I forgot to mention but you don't want to take up more bandwidth than necessary to sound good, 3.5 KHz is acceptable and limit the lows, as there is a lot of wasted power in LF and voice actually becomes harder to understand when bassy. Some guys run high-end mics and if the conditions are really good, it is nice but just a little QRM (noise, etc.) makes it harder to understand.
Commercial AM stations run the DC to the class-C amplifier thru a large choke (reactor) and put the audio across it thru a capacitor to keep all DC off the modulation transformer so as to keep from biasing the core of the transformer and limiting its LF response by lowering the inductance because of the DC bias. Every ham radio modulation transformer I know of is built so DC can be run thru the secondary and not bias the core excessively.
Once when I tried making a SE 833A I used a push-pull transformer and frequency response below about 80 Hz was seriously distorted - still perfectly good for voice but a PP transformer is not made for DC thru any of its windings except, of course, the primary where it is in opposite directions to the plates of the tubes and does not bias the core.
The first and one of the cheapest form of modulation was to load the plate of the modulator tube across a choke. This is usually a SE modulation stage and low power. You can also modulate the screen of the final amplifier or even previous stages providing RF to the input of the final amplifier but then class-C may have to be changed to something more linear. These are the cheap ways to get an AM signal on the air but not very efficient or effective. You end up with weak audio and may never be able to reach 100% modulation. Takes a lot of "iron" to make a powerful AM station.
Search for, "Gates BC-1J 1000 Watt AM Transmitter" if you want to see a classic AM transmitter schematic.
What an awesome tour!! I wasn't expecting the Geiger counters! lol
@@fjs1111 I couldn't think of that word "Geiger counter" while making the video. The challenges of an ageing brain. My grandson and I, and others, have made a few trips to Trinity site and made videos of it - lots of people have - but we made measurements and can see that it is about 10X more radioactive there than in, for example, El Paso. That is still not really alarming but it can be measured with simple devices like the vintage CD (Civil Defense) Geiger Counters. I had a "nuclear stress test" a few years back and the Geiger counters can detect me at a distance of 20 feet or so. You are seriously radioactive for a while after the procedure. My wife had a PET-CT recently and the same was true for her but her radioactive level was gone in one day whereas mine was detectable three days later.
@@ElPasoTubeAmps You got quite a collection of tubes. Really enjoyed the videos. The mercury vapor rectifiers are awesome too. They need a very high voltage though right? I've seen videos on youtube of some large mercury arc rectifiers for powering subways and they are something awesome to watch!
@@fjs1111 MV rectifiers don't need to operate at high voltage and can be used just like a 5U4. The voltage drop is constant and about 15 volts unlike a high-vacuum rectifier where the voltage drop increases with increasing plate current. A pair of "little" 866A rectifiers can power a transmitter at 1500 watts or more. I can see them almost as the solid-state rectifier equivalent of 100 years ago. I have watched those videos of rectifiers for subways also. They are beautiful and somewhat terrifying. I would keep my hands in my pocket around them... anything that has thin wire with lots of insulation and sizzles when it is on should be treated as deadly...
@@ElPasoTubeAmps I had missed the part about the Nuclear stress test, wow I never gave much thought to that but for the machines to detect it you must be a fairly powerful emitter! Thanks for the mercury arc info, I was thinking more I guess of the high voltage one's that look like a octapus. Look forward to your videos to come!
I was pretty sure I'd find new comments here today :O) Bless you 🙏
Great video Dave. The only part you didn’t cover was the rf exciter ? Where does the rf frequency drive get into the mix? Was it the Collins transmitter on CW?
GOD BLESS
Yes, it is the Collins transmitter on CW that provides the carrier frequency. A couple of issues using it - although it works "great" it is from 1947 and does drift slightly. Not enough to be noticed by anyone listening on AM but often times others listen to only one side band as if it were a SSB signal and in that case, the drift causes the carrier to appear and people get annoyed by that - I can understand - also it is 15 watts (actually about 18 watts) which is plenty to drive the Millen amplifier but sometimes too low for other amplifiers. I have an old iCom (circa 1995) that I basically use for a VFO (it has an audio problem) and it puts out around 75-80 watts of carrier and has a stable VFO. I have built a 4-1000A amplifier, grounded grid, that I keep on 40M and drive with a new iCom 7300. Took some getting used to the software defined configuration but I finally got there. The iCom 7300 is a nice radio. I can understand why there are so many out there. Thanks for your comments. I have some ideas for more videos - just got to go to the shop and get busy. 73
David, do the cats have their own call signs? And are they on 20m or 40m? Bet you find the controls all over the place in the morning from where you left them the previous night. Do they change coils on you?
Keep well.
EJP
I haven't gotten them on the air yet but I do have their names in my passwords. The two that have been in videos for years have passed away - both were 14. A new beautiful cat has taken up with me. They find me, I never find them. This one I call, Pretty Boy, and is a full blown Tom-cat. Very affectionate but has to go out every other night and be with the gang... got him fully vaccinated and microchipped. I think I am ready for the microchip so I can just walk into stores and get what I want and they send me the bill.
My theory is that every cat lives in three houses. As they say, dogs have owners: cats have staff.
@@EJP286CRSKW I sometimes wonder if my new tom cat, Pretty Boy, is two-timing me. Living with me for a couple of days and then living with someone else. He is beautiful cat. When he wants treats, he just walks up to the cabinet doors, stands on his hind legs and opens both doors at once by grasping the doors at the top. Where did he learn that? I wish I was as young and strong as he is - I may have been a long time ago... :-) As a kid I remember old people talking of the, Fountain of Youth. I thought, at that time, what is their problem ? why don't they just grow up and act their age. I understand now... Remember me saying cats choose me ? maybe I smell like chicken. The last dog I had was when I was 16. A wonderful female English Setter. We are doing OK right now.
I hope everything is ok with your family
🙂 As you mentioned the RF amplifier being on top and the modulator in the middle, I had immediately thought of a Linear amplifier. Is the a way to add the secondary of the modulation transformer from the modulator to a Linear amplifier? I want to believe there is a way but I do not have the full understanding, so maybe not ??? Great Video with great explanation, Thank you.
I should had mentioned as well also adding just a transmitter in general with out its original modulator. In other words using the Linear as the final of the transmitter of sorts. I understand you have to have an frequency oscillator along with a crystal or use an VFO/DDS in order to create a Carrier.
Love the shack Ray! I run A BC-610E Still :) But I didn't have it last time we spoke on 20m though. I hope to find ya again sometime . 40M has been good for AM lately. What tube could be a good substitute for the 250th if I ever needed to do a retrofit my BC-610 using the stock iron? 73
Hi Tom,
A substitute for a 250TH - Wow... I have never built with those tubes although I think they are beautiful. A 250TH is considered a high mu triode (mu = 37) back in its day. 5V, 10.5 amp filament. I can't think of any tube like that with that four pin base, etc. I still see them on Ebay usually for a reasonable price. I can tell you that the 4-125A is a good substitute for 810 tubes as far as performance and specs go but a lot of hardware changes would be necessary. I bought four 304TL tubes a couple of years ago that were a beautiful quad and by the time I got them, three of them had the filaments broken out. I am convinced they were good when sold, and the seller gave me all my money back, but I bet they were destroyed in shipment. Same thing has happened to some 813's I have purchased. Filament busted when I get them, and again, get a refund but I feel like shipping these vintage tubes is likely to be the end of them so that is a big problem. Maybe finding one at a hamfest is a better idea? I have had at least one BC-610 in my life, maybe two, but I know I parted them out and have no idea where all the parts went. That was decades ago. I do run what I think is a BC-610 modulation transformer in one of my AM rigs and use a pair of 4-125A into the transformer to modulate push-pull 812A in a James Millen amplifier. Gave me exactly the right impedance ratio but the modulation transformer I have is a UTC and is round and potted but it has the Z ratio of the BC-610 transformer. Anyway, hope to hear you on. I hang around on 40M and 20M and run a homebrew 4-1000A driven by a 7300 on 40M and keep my Collins stuff on 20M. 73 WA4QGA
@@ElPasoTubeAmps Thanks for the info! Much appreciated. If the time ever comes I'll probably have to change out the socket to except a different tube altogether and may not be worth the effort. But I'll buy a 250th when I get the opportunity to possibly avoid the hole process . The old girl is running good at the moment. 73 Ray I'll be looking for ya on 40m in the afternoon!
Hello,
Question, if your rf amplifier has 1250vdc and your modulator is providing 2000vac when you provide 100 percent modulation, you'll have 3250 positive but when your 100% negative, does that not take you below zero as 1250 minus 2000 is minus 750 plus your keep alive and you would still be negative 1150 with your keep alive at 100 volts. I know you said 75 but thats even worse according to your explanation. If I totally misunderstood your explanation please forgive me.
Can you elaborate on this as it does not add up according to my interpretation of your explanation which made sense until I thought about your actual voltages.
Thanks and great video and I plan on building an am station with a modulation deck
.
Keep it going, love your content!
I understand your question although I have never thought about it that way. You have the voltages correct for RF amplifier and modulator as they are separate power supplies. The positive peaks are around 120% and can peak up a little more and the negative peaks would, as you mention go to zero and shut the RF amplifier off and do all those terrible things called "splatter". If you overmodulate in the negative direction grossly, it just keeps the carrier shut off for longer if you don't have any kind of negative modulation control. It doesn't go negative in the way you explained it but maybe it would without this circuit. I have never heard it thought of that way and what you say seems to make sense but for reasons I cannot explain it doesn't work that way. Or maybe that is why the carrier is shut off for longer periods of time - i.e. longer gaps between the sine wave assuming we are modulating with a sine wave. Again, I have seen this so this is why I am trying to explain it this way and, as mentioned, the carrier would just be at zero for a longer period of time without the control circuit and your analysis would be correct - I think.... The seemingly insignificant 75 volts doesn't seem like it would work but it does. No matter how negative the peaks go on the modulation envelope, 75 volts remains to the plate of the class-C final and keeps it from totally shutting the carrier off. I don't know why or how to explain why we don't get the algebraic sum of these two voltages and it end up negative but it doesn't. Maybe I do, actually..... lets try... I don't have the schematic in front of me at the moment but I bet if we examine it closely one of the diodes probably ends up reversed biased and won't let current flow past the zero point. Seems like there is a capacitor there that shunts the modulating signal to ground - I am grasping as straws without the schematic. I have even read that some guys have controlled negative peaks with as little as a 9V battery. I cannot confirm this and surely it would be on a very low power transmitter. I can't do it now because it is 4:15 AM and I need to get to bed. 🙂 but I bet it is something like I was rambling on about above. 73 better go for now...
Thank you! Can you share the schematic with us as I now have AM fever and I'm going all in/ out!
Your explanation makes sense but I do have a few more questions.
Also, I am building a clone of the 30k1 and ild like to see if you could do a video or a chasis for 2- 3-1000s ? This is one of the decks I plan on building and another deck with 3 x 3-500z or 3 x 4-400s in a triangle
I think the 2- 4-400s look great but scoot them back a couple inches and put another one in the middle towards the front and peoples heads would spin off. Nothing like 3 tube amps. In fact, I've been looking for a LK-550 and they are unobtainable. Amp supply co used 3 x 3-500zed in that amp and I've never seen one for sale.
Thanks for your help and great content
@@jaredmahan4090 Check out QRZ page for K0JJF as he built a three tube amplifier as you describe. I don't have a schematic of the transmitter other than the James Millen schematic that can be found on the Internet.
A pair of 3-1000Z would be quite the project. You know each tube needs 7.5V at 21A. It would be difficult to fit it in the 30K1 cabinet. My favorite tube has always been the huge 833A. I love that amplifier. It has real balls...
73
What is the power consumption to run those levels of AM, if you don't mind me asking please?
Ever since I read your comment, I realize I need to make those measurements. I will get back with you soon. I am going to guess about 1 KW. Years ago when I built my 4CX1000A and at its max rated carrier output power of 1680 watts, the input was right at 3 KW. That is 56% efficiency. I figure AM is a little less efficient than that.
Hope all that gear didn't get to the basement via that stairway. Nice video.
Every ounce of the equipment came down those stairs with the exception of the Collins 30K-1 which was brought in thru the basement door where the big fan is. That was not really a great idea as I look back on it. That happened in 1993 when I bought this old house. Myself and a friend brought it down the outside basement stairs and I was only 43 years old and a lot stronger. Like to have killed both of us and I am sure I removed the internal components. That steel cabinet Collins made back in 1947 must have gained weight over the years... When we did get it to the basement I remember looking at my fiend and we were both happy to be alive and I remember saying that I will never try to take it out of the basement. There is also a safe in the basement that I had a couple of whimps help me with and it almost got away coming down the steps and would have squished me had it gotten completely away. I think it was 400 pounds. A friend and I, just a few months back brought the Collins 30S-1 down the stairs but it is only 180 pounds so that was not too difficult.
Fan is there to keep the litter box cooled. And don't let the group on 3840 hear you say that antenna tuners are a good thing. It's a Resonant dipole on coax cut for 3840, nothing else will get out.
I don't have enough room for any type of 80 meter antenna except for the Isotron I put up a few months back. Not too sure about that Isotron... very narrow bandwidth and I have never made a contact with it - I have to admit, I have not tried very hard. In the early 70's I ran a homebrew KW AM station on 80M in Huntsville, AL. I loved the guys I made friends with back then. Ran a single class-C, 4-400A and plate modulated it with a pair of 4-400A. Not sure if I will ever go there again. I have listened to some of the guys on 80M and some sound pretty good but some are over modulated and splatter. Those are the ones I was thinking of when I made some comment about splatter. I used to be hard-nosed against antenna tuners also but that is not warranted. They certainly can make the transmitter happy and that is not a bad thing... As far as helping a signal radiate or receive, I am still not totally sure but I don't think it hurts in any way.
You are the only one that noticed about keeping the cat box cool. No one wants an over-heated cat box... :-)
I wish I could build a Williamson amplifier from you as a mentor my father just passed and we where in the process of making one together
I am very sorry to hear about your father. Sometimes live gets hard. My beautiful wife of 45 years died on June 19 of pancreatic cancer. We didn't even know there was anything serious wrong until the end of February. It only took four months. I took her to the best hospitals, MD Anderson in Houston. She passed here at home and in out bed with my son and me with her. It's tough sometimes for sure. I have wonderful friends around and some of them played music for Marilu just before the end and I posted the video. Comments are disabled and I really can't watch it much but the music is beautiful. Stay busy, not insane busy running around like a mad man, but it's just not our turn yet. We all have to go there and I completely believe we will be back with all our loved ones when we pass from this life on Earth. Life here is certainly temporary. I hope your father passed peacefully and I am sure he is doing just fine now but we sure miss our loved ones. 73
Thank you so much I did watch the last video it was beautiful I’m so sorry
I’m happy you are moving forward and showing and teaching us about electronics I find them like treasure and have the same energy as you i just lack the major knowledge I know how to assemble but not engineer I find it takes so much time that I don’t have
My dad left me his work bench with every tool known to man and hardware mostly from USN
@@jimcatanzaro7808 Your dad's workbench is his and you can make it yours with his influence. Just because our loved ones are out of this realm of life does not mean they are not with us. It is a slow and painful process to move forward but it is up to us to do it. No human or spirit can do it for us. I see my wife as a daily influence in my as you must see your dad's influence. There are no instant and painless answers but you are blessed and given the energy to move on. It would be much easier for me to just give up and die. Seems like the easy way out but with all love and respect, find the value in your loved ones and friends and allow them to help you. I don't mean become dependent on them but receive the energy they can give you while they can that you can build on. That is what is working for me.
Aren't modulation transformers more or less unobtanium these days? Unless you happen across something at a hamfest but then what are the odds of it being exactly what is needed for a given project?
Modulation transformers could be considered unobtanium except for those that won't give up... they can be hard to find but continuous looking and luck is how they are found. This transmitter uses a modulation transformer from a WWII, BC-610 which ran 100TH modulating a 250TH. It is AM so the 250TH is running class-C and you can figure the load impedance of the 250TH by simple R = E/I - the plate current is essentially constant for a class-C amplifier varying little under modulation. If you can't find everything in the BC-610 manual (and you probably can't) you go to the Eimac data sheets and see it wants 2000V @ 250mA so we have R = about 8K - that is close enough. Then to the Eimac datasheet for the 100TH and you see it wants 15K for 2000V for a class-B modulator. So now you have a pretty good idea of the turns and Z ratio of that transformer. Z ratio is around 1.88. I don't think that is perfect but it is close and gives something to start with. If you have an impedance meter, you can start doing a series of measurements with different loads and figure the Z ratio out exactly - or you can just do the turns/voltage ratio measuring voltage into one set of turns and out of the other set of turns (carefully... with low voltage so as not to electrocute anyone...). Now you know your modulation transformer. Then you find or figure out the load your class-C amplifier that you are going to build needs and start selecting a set of push-pull modulator tubes to match the other side (the primary side) of the modulation transformer. In my case, I found that a pair of 4-125A running (I think AB2) needed exactly the Z presented by the transformer so that the secondary Z to modulate the James Millen amplifier running push-pull 812A was practically a perfect match. I think careful measurements revealed this BC-610 transformer was a turns ratio of something like 1:1.6 if I remember correctly which would be a Z ratio of 1:2.56 which would make a 8K load reflect back to the modulator tubes as about 20K. Eimac datasheets will tell you what the tube will actually do if you give it the voltages they specify. My AM transmitter in this video is slightly more complicated than some as I use separate power supplies for the modulator and class-C RF amplifier. I run 2KV on the modulator tubes and 1250V on the RF amplifier.
I don't think you ask for all of this but it is a thought and action process on figuring out how to use a modulation transformer to make it work with a number of different tubes. In many cases this range of turns/impedance ratio is close in to what I have shown in many modulation transformers and the matching does not have to be perfect. Lastly, most all amateur radio transformers are designed to have the class-C plate current pass thru the secondary of the transformer and not saturate the core. If you look at commercial AM transmitters, they use a huge choke and apply the modulation across that choke and separate it with a capacitor so no current flows thru the secondary of the modulation transformer so as to improve the HiFI quality of the signal for commercial broadcast purposes.
It is rare to find high level modulation transformers and I have the Mother of them all - an 85 pound multi-tap UTC transformer that I hope to use some day. For now, it is going to be hard to beat the 300 watts of carrier, fully modulated, that I get from the James Millen amplifier running push-pull 812A tubes. Hope this helps.
@@ElPasoTubeAmps It does help and thanks for the walk through. So... it seems I should keep an eye out for whatever interesting transformers that might come my way and then find a compatible project to use it. My thought previously was to pick a project and then try to track down the parts and it just hadn't occurred to me to use an available transformer as the focal point for a project. Anyway, thanks for the reply and perspective.
@@MikeBenedict1 Huge projects have started for me from a single hard to get item. I was given several new 4CX1000A around 1982 that spawned 40 years of amplifier building. My wife and I found a beautiful turquoise oven for $50 that built a $10,000 pergola... lol.... I can stare at one single item and build a world or projects around it. Keep building. This seller often times has a good transformer selection.
www.ebay.com/str/audiopathicdistractions?_trkparms=folent%3Aaudiopathicdistractions%7Cfolenttp%3A1&_trksid=p3542580.m47492.l74602
If I were building a new AM transmitter, I'd use a Class-D PDM modulator, which doesn't employ a transformer. In that scheme, the modulator performs as a switching regulator. The audio is converted into pulses of varying width, by a ramp generator & comparator. This is amplified and applied to the grid of the modulator tube, which is in series with the P.A. plate. The modulator turns on and off, which provides much higher efficiency, than it would if it were linear. The P.A. plate L-C circuit provides the integrating action, which converts the pulses into audio. A diode stack suppresses the inductive kick-back (like the damper diode in a TV fly-back). This modulation method provides much better efficiency than a regular high-level linear modulator. The only disadvantage is that the P.A. requires a much higher B+, because there is no voltage step-up from a modulation transformer. In the 1980s, I was in charge of the "care and feeding" of a 50 kW Harris MW-50A AM transmitter, which worked this way. The modulator tube was a 4CX5000, the P.A, a 4CX35000, and it employed a 24 kV P.S.
@@Pootycat8359 I don't know why but I have always had a fascination with high power transmitters. Your Harris transmitter is certainly impressive. I still have a pipe-dream of coming across a vintage Gates with 833A or Collins with 4-400A and putting it on the air but it may not come true and that is OK.
Honestly, I have been very impressed how well 300 watts (carrier) of AM compares to SSB of 1500 watts. The 1500 PEP watts of SSB does "outperform" it in its own way but everyone seems very pleased and comments on the quality of a good AM signal and even seem surprised by its S-meter strength.
Thanks for your information. I find it very interesting,
Hello im midway through a build of a similar setup. My problem is finding a appropriate modulation transformer that can handle 2-5 hundred watts or more. Any ideas??
The modulation transformer is the biggest challenge. It is also important to get the impedance of the modulator and the class-C amplifier correct. What are you using for modulator tubes and what RF tube are you going to use? I may be able to help but I need to know the voltage and current of the class-C amplifier and the same for the modulator. I have found what I want more than I ever imagined but it took years of looking. Get acquainted with other AM groups. They may be able to help. Check out this seller. Sometimes he has modulation transformers and I buy a lot from him. 73
www.ebay.com/str/audiopathicdistractions?
_trkparms=folent%3Aaudiopathicdistractions%7Cfolenttp%3A1&_trksid=p3542580.m47492.l74602
This is the ultimate multimatch transformer. 600 watts. I have one of these and use it with a pair of 3-400Z to plate modulate a GG 3-400Z running class-C.
www.ebay.com/itm/196223041404?itmmeta=01HW718DKF7JSSJRH635D7GSEY&hash=item2dafcdff7c:g:GM4AAOSw1xBlvKqb&itmprp=enc%3AAQAJAAAA8BCwNJyeqWbLkG50v12T7oPwewoqLtWE%2FBSkD1KK0nGXR0w8Dybb7naWaNQQTRPD5jnUI1j9K84hR8qgsxL9wG3jJWQOPQlZUM5uuTOHR%2BEHO110yTG2vutR%2BxcV0c3gaRDqj9sAL1yaZwKrQCYNQ01JVtgvSnZuN%2B6TJ4TWBZdS89qoyOx2f%2FC6jV62Mn9zMnUJbp%2BPe2RfcBd1M0twiCosg2t%2FFqdyezKPKt3sTzpCPR7QY0SGfhHa2OW0%2BuB4Q5Hrh%2FFRmcBUTprTrkCTWy36a3NEVYDUhlesdsY%2BfEsvnYvTT32Pr0%2BrMlFZ%2F7EMcg%3D%3D%7Ctkp%3ABk9SR_jZoeHhYw
Besides power level, it is all about the impedance values you need for the modulator and the class-C stage.
www.ebay.com/itm/116083109330?itmmeta=01HW718DKF5SJABNZYRHNBRQR9&hash=item1b0717add2:g:UXIAAOSwNWll3ibP&itmprp=enc%3AAQAJAAAA8NVTjVDoQXMlNqtskrdDHo5zTGMZ--JUr3HnV8WPB%2FrJnst3L1f0%2F06o4ZUUP42ismzn7yI7O3P5Q7dt%2Ff429q3oD338Gt%2BsFt%2BWzPKv%2BxfP8%2FUR8H922s3W2W8UYTbT4CVXSsAysZrxe0RL6uE2r4U066X21YMPDW4eRFdgIXrKxfl%2BHCplYbEH%2Bfnd4dynpdTYAnB%2BebnVaOH1CBgnd3pYqVp2ABBgznrm3iSCax7PjEuAuASPKYyChoacTFIWZ%2Fna278JIYMxcPdachSzbU3xd5S0clYBEQbbHR22wpMKbbfPQ6TUNcgJ8RU09AYCzQ%3D%3D%7Ctkp%3ABk9SR_bZoeHhYw
@ELPASOTUBEAMPS
I'd like to find a duplicate modulation tranny as you have with multi tap primary for the options. I've been searching everywhere for one of those. (Please help) Depending on iron available, I plan on using a pair of 4-400s modulating a pair of 4-1000s/8166 or something similar. I know it's overkill but I like two big glass tubes vs 1 tube.
I have the dream-come-true modulation transformer I am willing to sell. It weighs 85 pounds and is the UTC VM-5, 600 watts. I know it works as I have used it with a pair of 3-400Z to plate modulate a 3-400Z, grounded grid, class-C for AM. I did have to mount it in a large ammo box as it "talks" a bit loud under modulation but it will match anything. Here is one on Ebay so you know what it looks like. www.ebay.com/itm/196223041404
Here is its spec sheet. amfone.net/Tech/UTC/UTC.pdf
You will have to come get it - I can not pack and ship it. I will take $250.
Where is your
COBRA 29, ?
Power mic.
That's a different video... 🙂
Everyone needs a Dummyload! lol.