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Building a better End Fed Half Wave Antenna for Ham Radio?
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- Опубліковано 7 бер 2024
- In this video, we take a look at various End Fed Half Wave Antenna designs for Ham Radio. We discuss a little about the history of EFWH Antennas and some design considerations.
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Son, you're making my head hurt! Glad there are smart peeps out there to figure this stuff out; appreciate you're showing the process!
Glad to “help”! Really my buddy Ziggy deserves the credit here, he’s been talking nonstop about this type of antenna so I had to make one. I’m sure there will be more to come in this one 👍
You're the one giving me wisdom. I like your deduction that your NanoVA wasn't providing sufficient current for inductive coupling. 73, KF0NNQ.
Thanks for watching Bill, much appreciated 👍
Looking foward to the revisit of this after testing
You and me both brother, thanks for watching Shane 👍
There is always room for improvement, can't wait to see what the outcome is ! In Ham radio, everything is experimental and fun ! AA2BD Big D 👍
Well it might have to get a field test
I think thats the plan 👍
Snow blowing will have to wait for now. Time to go the bench and slap on some caps on the secondary’s and have some fun. Thanks ape for the fun and practical videos.
Hey MrMud, thanks for watching.
Looking forward to what you find. Cool design.
Thanks Tim 👍
That is some fine material to digest. I think you are correct that you are not getting enough current through the system for the coupling to take place. I would think with the capacitor across the secondary it should bring the high bands closer in VSWR to the lower bands. Really cool discussion. This is why the CaRH folks and their best teaching channels out there. Bravo
Hey John, thanks for watching brother. I'm always looking for something that might be a little better and if not... I enjoy the ride. I am new to this particular type of configuration so it will be fun to experiment and hopefully I will learn something.
It will be interesting to see the test under load results. I had forgotten about AA5TB's site. Lots of good information there!
Thanks SF, this was just something that I was playing with the other day. There will be more to come but I need to get a few other projects completed. Stay tuned 👍
It's all about the pronunciation. 😂 (Now all kidding aside...compare the image at 9:20 with the schematic of the Johnson Matchbox, and you'll see why this is the CORRECT placement of the capacitor.) Nye Viking knew exactly what they were doing. This is also why it is important to fact check designs against proven ones from decades ago. I can't tell you how many times I've seen schematics copied incorrectly and used that way in publication after publication. Always "trust but verify". PS, this UNUN can also be modeled in SimSmith for those who wish to take it to the next level. 73
Yes!
Ah, you added to the comment. Thank you Hollywood, I will go look at the Johnson Boxes 👍
Impedence matching.
When matched you have maximum energy transfer.
Look at the impedence on the VNA, and not so much the SWR.
The transformer-cap--reactors--are the transmission between the radio engine and the rear wheels antenna.
Get a thermal camera and "see" where the RF power gets used up-hot cores- indicate poor matching and or improper core material composition.
That twisted primary is where they get you!
Yes it is!
You're such a great buddy, buddy!
lol 😂
Interesting and informative on the detail you guys put into your products. MM0OPX has a good design, and I’m keen to try your one. Bit of an antenna farm going on around my property now.
Hey ToiToi, Colin (MM0OPX) is a great guy and I am lucky enough to call him a friend. I was tipped off to this design by another friend, Ziggy, in it seems like it will be fun to try and work with... that antenna farm sounds awesome! Thanks for watching.
Yes I played with this type of windings. It seemed to tune up very easily 80 -10m with some very low swr in the right places but would get fairly warm at just 50 watts
THanks for the info, I have yet to hook this to a transmitter but I will keep an eye out for heat... thanks for watching 👍
The relatively low Xc of the cap on the output is going to heat up your core because it's shorting out your signal. The old books showed the variable cap in there to tune to match the XL of the output winding of the turns of the output. This creates a tank ckt and it will be very good at a small band of frequencies. Everywhere else it will look like it's trying to short things out.
Will it work anyway? I've made contacts on a literal dummy load. Of course it will work anyway. But you're shooting yourself in the foot unless you know how it works and build your equipment properly.
But what do I know? I'm just a bus driver for RFI.
What length of wire did you use to get this configuration to tune on 80-10m with low swr? I would like to give this a try, but not sure of the length of wire to use.
@@thebarneylejeune efhw
I’m looking at making my first efhw. Maybe 4 turns primary to get induction to work. I’m digging the double core 4:1 balun. Very quiet on loop. Still have to test on 66 ft OCFD. Thanks as always. I’m Leary of capacitors.
I’d look at using the 49:1 with two primary and 14 secondary for the 66’ end fed. Good luck with the build 👍
That looks a bit like the unun design that is described by the guys at ocfmasters as well... I've built one and just haven't got it hung up yet to test 😁
Hey Wayde, I have never heard of them but I think you are right, I need to look at them some more. Thanks for the info, it's helpful 👍
I have built several of the efhw antennas without adding a capacitor (there is probably some inevitable capacitance created by wraps of the coils). It doesn't seem to make a lot of difference from what I've seen. Thanks for sharing! 73- AA4K
What I have seen is that they don’t really matter much at lower frequencies but to help matching at 20m and higher.
NanoVNA output power is somewhere around -9dBm. The bigger commercial benchtop units are around 0-15 dBm. You might need to step up to one of the big boys now 😜
Hey Jeff, we’ll figure something out. Thanks for watching and for the comment 👍
hi sotabeams used to do one with veriable cap for qrp and you just tune to loudest on rx and it was 1:1 using 40m tx wire and 5m counterpoised elevated to 1m off the ground and the first time i used this was after a thunderstorm with inverted using a 10m mast in the middle and i worked japan from uk on 5watts so very lucky and the ease of changing band u just turned the cap and away u go very simple worth making M0DSY
Thanks for the info DB, I will see if I can find any info on it 👍
@@TheSmokinApeI also made a 49:1 with a core from mouser and at 21m 6ft off the floor it tuned 80-10m without an atu I used rigexpert to tune the balun it took some doing but my mate tried it and got Indonesia on in and it was working into Spain/germany /ussr turkey on 80m he’s over the moon as he used around his fence in a u shape and works lol it’s fun tuning ununs & baluns using an analizer love the channel and thankyou for doing an Exelent job 73 db
This is what I call an "isolation transformer", you get extreme amounts of common mode rejection. I use 5 turns : 5 turns to couple signals into my SDR this way, it is very lossy but can do good things for your receive. This transformer is similar to the LoG antenna transformer.
I'll build one of these up and post the results on discord.
Thanks for the info and for playing along GDL 👍
Great content! The next great antenna hasn't been invented yet!!! Sometimes I wonder how many antennas were mistakes...🤔
Hey West, I bet more were mistakes than we are lead to believe, I do think the best is yet to come. What folks need to do is better understand where we were, where we are and how we got here... at least that is what I am attempting and it's been pretty fun. Thanks for watching 👍
Just some thoughts from my understanding. The capacitor has been added to bring the higher frequency Swr sweet spots into the ham bands. One advantage of a dc ground when the primary and secondary are connected is for high voltage protection before the coax enters the shack.
A side note I heard is that capacitors tend to fail shorted. I think it was a power supply repair video. It was an argument to use two capacitors in series. If one shorts you don’t get a short across your coax line.
Thanks for sharing your thoughts on the EFHW.
Thanks for the perspective and for watching Stein 👍
@@TheSmokinApe This is a 15 minute on paper summary of the 26 minute video that showed the measuring that he did. ua-cam.com/video/MzfQybYMlUc/v-deo.htmlsi=g2gsWrzHrQsYZ4Fv
Great topic. Hallelujah, where's the Tylenol
lol, thanks for watching Shooter 👍
Fuchin good video.
lol, thank you 👍
It might be interesting to see what the Fr is with the 100pf cap on the secondary vs what the Fr is with the cap across the primary winding with two and three wraps. IDK, i'm just wondering. Then if that leads to nothing, connecting it to antenna to see how it deals with the reactance and resistance presented by the antenna. At what F does the circuit go to parallel resonance, infinite Z? There seems to be mixed reports between using shunt caps and not....
Hey Watt, I definitely need to experiment with it more but I have a few other projects going on at the same time. Hopefully I get an update out soon. Thank you for watching!
interesting video
Thanks Thump, I needed something to keep me busy...
That a great idea to test. so far i have not wound that way. I would say make it as a antenna and check SWR at 1/2 watt or so. ICOM 705 will plot a SWR graph. what I have done and it works great is no cross over on secondary winding. ant lead will come out near the input. that still tunes fine with the 100 PF cap on input. the cross over half way is so ant lead comes out opposite of the input. also the twisting does not matter on primary . in fact you do not need that at all. do first 2 wraps run the tap .then continue 14 turns . cross over if you want. the tap is the ground . the 2 turn wire wrap is input and end of 14 turns is ant. that works and tunes the same. but your first prototype buy twisting the first 2 turns and cross over at 8 is the easiest and best for winder base you are using. I did a 2 stack of FT 240 type 61 . 49:1 with 3 KV 100 PF cap. made of 10 AWG solid mag wire. using 2/14 turns . tunes great 10/11/12 meters adjusting wire a few in. I put different color heat shrink for 3 bands. up a DX commander 10 meter pole and counter poise and choke on coax at antenna. 1.3 SWR or better . and ran 500 watt FT8 on 10 meters. 2 stack of T240-61 stay cool. my tube amp wont do 500 watt FT8 long so was a short test. but 250 watts ran hours no heating. same thing done with type 43 mix. got some heating and slight higher SWR . still under 1.5 :1 . found type 61 on 10 meters runs tad better. I can say the 31 mix gave bad SWR . on 10 meters. never even tried on air. that meant for common mode choke. I have a thermal imaging camera as part of my work as a electrician . when using smaller AWG wire I can watch the wire heat up before the toroid. when the wire is heavy like 10 AWG the wire stays cool then after a wile the ferrite ring starts to heat up. neat to watch. 73's
Hey Robert. I haven't done the tapped winding yet but plan on it... thanks for watching!
@@TheSmokinApe just do the 14 turns . the one side is ground. tap at 2 turns is the in. 73's
Thanks Robert!
As a neewbe, are you using only solid core or stranded wire, it makes a difference in my amplifiers I build.
@@stevensullivan3121 I used solid core for the secondary and stranded for the primary
I can't provide any feedback besides great video on an interesting topic
Well, thanks for checking it out Joe 👍
I don't think it's an output power issue of the nanoVNA, but you may be right. Have you tried using a longer transmission line between the nanoVNA and the transformer? Transmission line length can play its part in reflections. I'd be interested to see what the sweep looks like for a 5m long and/or a 10m long transmission line between the nanoVNA and the transformer.
Also, I'd try more primary windings if you can, while still maintaining your desired ratio. That would also be another good test, in my humble opinion.
Hey Bob, I have not tried longer transmission line. I was just messing around with the design today and though "I should make a video". I like the idea of more wraps on the primary, thanks for the suggestion 👍
@@TheSmokinApe Yeah, if your thought is not enough power from the nanoVNA, more turns on the primary would give you more source magnetic flux into the iron/secondary.
Only thing I can think of is maybe try getting the primary winding closer to the secondary winding. Might help the NanoVNA.
Also how is the efficiency compared to the typical design? Might not matter for QRO but might make a difference for QRP. Just curious and thanks for the video
Hey Iceman. I haven't got to the point of testing efficiency yet, I'm still wondering if this dang thing will work! LOL. Thanks for watching bro 👍
@@TheSmokinApe lol, all good. Looking forward to seeing what you find out.
Thanks man!
The one not connected is just galvanically isolated which does have the benefit of lower noise.
Yeah, I need to give it a field test..Thanks for watching 👍
Hey Ape, As I’ve said before You have way more experience with ferrite Xfmrs than I do, but from the research I’ve been doing the Cap across the Xfmr’s input is to minimize loss (not for SWR purposes) at higher frequencies, like on 10 meters. Also loss wise the testing I’ve seen prefers the Fair Rite 2643251002 core (43 mix, which is thicker for its diameter) and close wound in autoformer type windings tapped (not twisted) at 2 turns with 14-15 turns total for 49-56:1 ratio with a 120pf TDK cap IIRC (it would be interesting to see if your primary/ secondary configuration follows suit AND minimized CMC). It seems this geometry, and tight windings seriously helps to reduce losses and will easily handle 100 watts without overheating. And, Yes, the TDK caps are preferred for minimal losses...
SEE: End Fed Half Wave Transformers.......Are they as good as we think? - MM0OPX Field Radio
Best Ferrite Core For a 100w End Fed Half Wave Antenna - MM0OPX Field Radio
for a good videos on this.
Another is…
Trash that FT140-43! EFHW xfmr geometry STILL matters! - Evil Lair Electronics
Seem to be the (or one of) originator of this concept, BUT you need to ignore his jibes at others he feels slighted him. There are more videos that have tested this design (back to back xfmrs, and calculated) for efficiency, that back up these results.
Also from the circuits I’ve seen, putting a Variable Cap across the output coil is so you can Tune the impedance match from/to the antenna, and is a Variable Cap so it can be tweaked as you change frequencies / Bands. There’s Random Wire antennas fed in similar ways in various publications, usually not with coupling coils. More than one way to Skin a cat!
Keep On Keepin On! 73 mike
Hey Mike, thanks for the comment. I do mess with these things quite a bit but I don't consider myself an expert. I am aware of the work both Evil Lair and MM0OPX (Colin) do, in fact I am pretty friendly with Colin. I find that, at times Colin is surprised by his results leading me to believe he is genuine in his experimentation; Mr Lair, while informative, seems that his videos are to support a predetermined conclusion. What I attempt to do is is encourage; learning, research and experimentation so folks can decide for themselves what is best for their uses. I am sure I fall short at times...
What I have seen is that no core and configuration does it all... I think we all want; good impedance transformation, core efficiency, multiple bands and low Q... a lofty goal. I want to bring folks along for the journey, not tell them what to do.
THank you for the comment and for watching, I appreciate the support!
Hi Ape, just wondering if I could either get, or purchase one of the wire winders ???
It appears that your’s are of a higher quantity then I can find in VK land.
Let me know, thanks for all the knowledge that you, Steve,Jeem and Chuck have given us and keep giving us.
David Wilson (VK2AAW)
Hey David, glad you like the videos. We do not sell just the winders but complete kits, being in VK the shipping is brutal... If you want a quote; email coffeeandhamradios@gmail.com and we can see what we can work out. Thank you for watching the video.
@@TheSmokinApe Hi, thanks for your quick response to my question. No doubt I will be purchasing one of your antenna as part of my antenna setup(s).
The video was great and gave e me a moment to pause and think about my next transformer for a dipole I am designing. I live pretty close to the eastern edge of Australia, Les that 20km as the Crow flies, so anything I build should be provide good DX coverage.
Thanks again for the encouragement.
73
David Wilson VK2AAW
Good luck with the build David 👍
I’m sure you have seen Colin and using 2 transformers back to back. Then do a through test S1 to S2 and divide the results by 2 for loss.
Give it a try.
Yeah, I’m familiar with that test and have done many of them. I do plan on doing more “stuff” with this design in the future but was just messing around on this day and wanted to share. Thanks for the suggestion and for watching, it’s much appreciated 👍
I still wonder why we spend so much time on the transmit side of the equation. I wonder what happens when you release the PTT and start listening? In some of these antenna designs, where we are transforming, what does that transformation do to signals coming to our receiver. Especially weak ones.
Fair point and questions Don. I with the RX signal the transfor happens in reverse matching the antenna to the transmission line compared to matching the line to the antenna. That transformation does come at a cost so there will be loss on the RX signal.
Hi there I was wondering if you could help me with my computer problem? Well configuring my RTLSDR version four into my dell all in one windows 10 computer, I messed up. Apparently I goofed up the Zadig and now I cannot even login to my computer as my wireless mouse and wireless keyboard are no longer recognized, do you have any ideas? Thank you so much.
Sorry man, I don't think I can help with that one...
If the Nano VNA milliwatt output is not enough to magnetize that large core... how could receive possibly work through that core at a fraction of a microwatt level signals?
Think about it. 🤔🤨
Great point Mikey 👍
Ehh their too far out in the mudd anyway 😅
The capacitor only comes into play when you connect a resonant load (the antenna).
From my experience it lowers the SWR and changes the bandwidth (not the frequency) on the 10m portion of a 4010 EFHW.
You need to front load the antenna to bring the 10m dip down in frequency if it doesn’t fall where you want it. The cap (80-120pF) is to lower the SWR.
The NanoVNA puts out close to -10dBm to +1dBm which is ample voltage at 50ohms to test toroids and transformers. Receiver front ends work at -120dBm with toroid wound filters, do they not?
When testing transformers it’s better to connect two devices back to back. Connecting an assumed impedance substitute (a resistor) is far from ideal.
A right royal pain in the butt as you need to wind two of each.
I’ve lost count of how many toroids I’ve wound and tested for EFHW use but I’ve settled on a galvanically isolated design similar to yours.
Coil shortened antenna to reduce the 40m portion length and tunable from CW to Phone on the fly for 40m and 20m. I get at least 1Mhz of BW (VWSR 2:1) at 10m so no tuning is not an issue.
I get a full 200KHz (7.0-7.2 in Japan) on 40m with the dip tuned to the middle.
A good 3 years into this build though 🫠
73 John
"The capacitor only comes into play when you connect a resonant load (the antenna).
From my experience it lowers the SWR and changes the bandwidth (not the frequency) on the 10m portion of a 4010 EFHW." I've seen the cap make an difference when testing the transformation ration against a fix load like a resistor, In fact, I have videos showing it. What I typically see is it starts to make a difference around 20m and then higher.
"The NanoVNA puts out close to -10dBm to +1dBm which is ample voltage at 50ohms to test toroids and transformers. Receiver front ends work at -120dBm with toroid wound filters, do they not?" Great point!
Agreed, I typically do this but was just messing around and really didn't consider this type of winding something I would be serious about.
Thanks for the comments John!
Lemme rephrase that.
Fudging with the cap on the toeroid is pointless unless you have a tuned element (yup, that includes the counterpoise) on the secondary.
The wrong cap and what could have been 1.2MHz of VSWR 2:1 BW at 10m could drop to less than 1MHz… as an example of many toeroid fudging experiments.
So what looks nice and deep/flat/wide on the VNA with a resistive load does not translate to the best cap value when hooked up to your EFHW, most of the time.
As an aside, I see some people using vertical EFHW.
Might be an idea to do a PSA next time you do an EFHW or POTA video.
Several hundred volts of RF even in the 20-100W range at the feed point. Accidents are waiting to happen (children’s fingers and dogs noses).
73 John
Fight the Good Fight!
I’m trying 🍻
As an electrician it make sense!!!
As a ham, I’m not sure 🤨
MOTO, but if you're not seeing a change in the SWR sweep with/without the cap [on the primary]....there's something else wrong. I've made nearly a dozen EFHW UNUN's and every one exhibited change when adding the cap.
There was a difference with and without the cap, that was what I should in the pic of the sweep 👍
Hi Ape -- have you taken a look at Model 36130 - 36:1 for EFHW, 150 from Balun Designs? When I saw the loosely coupled transformer (poor description, but you get the idea) on the livestream, my mind immediately went to this one. Unlike the wrap around the iron core you were talking about, this is a broadband approach. But seems to require a few more tricks w.r.t. the radiating element and the counterpoise, to bring it in. It does look promising in terms of efficiency, though.
From the webpage: ""After much research and testing, a new transformer design for End Fed Half Wave (EFHW) antennas has been achieved. Developed by Bob Glorioso, W1lS and Bob Rose KC1DSQ, they discovered that most transformers for EFHW antennas used higher impedance transformations than necessary and were wound in a way that limits the high frequency response of the transformer."" .. I seem to recall that Waters and Stanton may have talked around this design a little bit, but I don't know if it was attributed to W1IS and KC1DSQ. I thought I found an article on this design, but I dont immediately see it in my files to give you the title.
Hey Kinetic, I have not seen that but I will check it out. Thank you for the info!
Is this the article you were looking for?
www.balundesigns.com/content/End%20Fed%20CQ%20Dec%202021%20rev1.pdf
Wow, thanks for posting that 👍
@@TheSmokinApemy pleasure and I love your curiosity on these things, which I somehow share. Haha. Look forward to see where it goes!
I always thought the reason to put the C on the primary side used to be the voltage rating:
Let’s say TX with 100W / 200Vpp and multiply that by your transformer ratio of 49 or 64 and the capacitor on the secondary side has to be able to deal with that. - Maybe that’s not an issue anymore these days, but maybe high quality 10-15KV capacitors were hard to come by in the early days.
The opposite is also true: Better put a high quality C with lower (yet still sufficient) voltage rating on the primary, than your cheap Aliexpress 3KV variant of dubious origin.
Please correct me when I am wrong: I usually am! 😜
Hey LabCat. I would agree that using the cheap caps for AE are probably not the best option. It' my understand the cap across the primary only needs to be rated for the input voltage as the transformation has not taken place at that point. On the secondary it's a difference scenario, and that would likely make my cap choice in the secondary a bad idea.
@@TheSmokinApe Well I think it's variable vacuum capacitors rated for 10-20KV where things get expensive... A fixed capacitor for 15KV should not cost an arm and a leg. But I haven't looked into putting capacitors on the secondary side and how much better or worse that works.
@@labcat73 I have a vari but no idea what it’s rated for 🤔
Talking seriously, magnetics is a weird topic. You suspect there is not enough current/excitation on the nanovna, but it might not be the case.
There is a guy in VK land, Owen Duffy, which tries to explain the physics of those high rate transformers, and seems to have a nice technical background on the topic. Unfortunately, his explanations lack a lot of details and I cannot grasp 30% of his claims.
One of the points he makes is about leakage inductance and parasitic capacitances, which he can model and measure very easily with a vna. I got to reproduce some of his experiments but I don't understand what I can change to improve it.
Anyway the one take away I got from his blog is that the capacitor on the secondary intends to create a resonance on a specific band, while the capacitor on the primary counteracts the leakage inductance and makes the transformer more flat. If you add a capacitor to the primary and the swr goes up, it might be too much or too little capacitance compared to the leakage inductance.
I should have paid more attention to my electromagnetics classes...
Thanks for the "encouragement" Rafael! This is helpfiu... 👍
@@TheSmokinApe You are doing one experiment I am overdue doing, and that might work great!
Things to try:
- adding smaller capacitors to the secondary. It might create that resonance, and although reduces the versatility of the antenna, might improve the radiation.
- playing with the primary capacitor. In my EFHW, one has 100pf, another 120pf, and one experiment I did, I added 220pf...
I was reading last night where someone recommended a 150pf for the 49:1. Thanks for the suggestion, apparently I opened a can of worms...
Maybe try and get the green wire wound as tight as the magnet wire. Maybe try with magnet wire instead.
I was trying, it’s stranded and PTFE coated which makes it slippery 😮
@@TheSmokinApe I feel your pain. Seriously, as long as you don't scratch it, the solid magnet wire should do pretty well. Doesn't look as cool though.
I got nuffin, I'd have to refer to my AARL Antenna book. Lol
I still have to build my Apollo, so do some moe testin' son.😄👌
Get after it son, you burning daylight 😮
Crazy stuff here SA. The cap will have about an Xc of 450 ohms at 80m and half that at 40m. You are sticking that mf (micro farad) on the output where ideally, it's what, 1800 ohms if it's a 36:1 or much higher if it's a 49:1 or some such. Have you ever heard of a path of least resistance, son? What the farad?
Is there less noise? Of course there's less noise. The antenna is shorted out.
Episodes before, I have asked you about XL values. I don't know if you found anything out or not but you need relatively high XL values looking into the input with that transmission line unloaded on the output, otherwise you are just shorting out your signals before they come close to the antenna.
If you want to make a balun for one specific frequency, a cap can work out well like this by making it a tuned parallel tank circuit. Your jX value can skyrocket which is actually a good thing in this portion of the design because we're not talking about the jX of the antenna which we want to keep near zero. But face facts. You're trying to build a multi band antenna and that's hardly a single frequency antenna.
This makes my head hurt. I want back on my school bus with unruly children. I can fill out reports on them.
In this case it would be 49:1. I think thise makes the most sense "Is there less noise? Of course there's less noise. The antenna is shorted out." of most of comments received. "Is there less noise? Of course there's less noise. The antenna is shorted out. " correct.
@@TheSmokinApe with the transmission line transformer totally disconnected, check the output winding XL. You would like to see that XL being 4x to 10x the desired output impedance, so if you are wanting it it for your EFHW @~2500 ohms, look for an XL of at least 10k. If you can't get that, as the old books show, you can parallel a cap in there matched to the Xc = XL. Then you will have a massive amount of impedance on the output and it will be much more efficient. But you're stuck on a small band of frequencies unless you can find a way to swap out that output cap to match the XL of the new frequency. The schematic shows a variable cap so it can be adjusted to match the XL on the fly. More windings will get you a higher XL.
Again, checking your unloaded input winding XL of a transmission line transformer will give you an idea of how efficient the input side is. It should be at the very least ~200 ohms. 500 ohms is going to be your 10x value at your input and a good margin target at your lowest design frequency.
If you are interested in efficiency.
Different size resistor?
So and EFHW is about 2,450 ohms and that why I used a 2,500 ohm resistor. Some folks debate the actual impedance but I have never measured it... this is a new configuration to me, so I still have some stuff to learn. Thanks for watching Jerry!
@@TheSmokinApe Looking forward to see where this goes next!
Not sure how my experience as an automation engineer would apply, it seems the way your wraps are laid out is not conducive to the inductance needed. I'm not an RF guy, so maybe I'm missing something here. Ferrites in my application are used to null transients and give a smoother response.
Hey Steven, in this case we are using it to step up voltage and change the impedance on the secondary side to match (attempted) the expected antenna impedance.
@TheSmokinApe TSA, thanks for the reply, am working on obtaining my Ham license. So will be finding out how these are used for antenna matching. Another totally different area of expertise, I work with high speed servo systems, it's all math, but trying to match different freqs to a singular antenna looks to be an impossible undertaking, hence the different antenna utilized. I like the esthetic of this device. PS, I also build vacuum tube amplifiers as a hobby from scratch, point to point wiring.
Steven
I would tend to agree that the VNA isnt the direct issue and nor is the Capacitor. If you stand back and have a rethink about it. All you have done is shifted the cap from the primary to the secondary side so two things come to mind a transformer is a ratio device isnt it? So if you have more turns on the secondary than the primary you are stepping up your voltage and stepping down the current and also stepping up the impedance but default. If you had 100pF at the primary and now you shift that too the secondary it now only presents less reactance back at the primary. But its voltage rating needs to change to compensate fot the higher voltage presented across it now. Ok thats the first bit.
VNA... as stated previously if the VNA can excite the transformer then you have zero hope this will be any good at recieve... think about that. VNA = -4/-9dBm. Wanted recieve levels are??? -120 to -60dBm...
What I think you have done is created a wonderful wide band choke something thats presenting a lovely 30-75 ohm resistave component back to the VNA. The give away was that if you remove the resistor nothing changed. If this impedance transformer was actually trasnforming like it should you should have near infinte VSWR when its either shorted secondary or open circuit as it should present either 0 ohms or infinite ohms, correct? And with the correct resistance it should present as 50ohms on the primary when terminated correctly on the secondary.
I think its your turns, turns ratio and ferite type thats got you stumped. But at present you have built a dummy load of sorts.
Anyway thats my 2 cents worth.
73
Thanks for the 2 cents Phil, it’s helpful 👍
Much more simple design...Maybe your on to something!
Thanks BA 👍
You make me question reality sometimes....
Ur welcome -Ziggy lol
Yeah, Ziggy brought this one to the table 👍
Make Jeem go outside to test it, LOL
Not a bad idea 😮
Ah yes, the "Fuchs" Antenna. I totally won't reuse that immaturely.
Lol
Dear Mr Ape,
Could you please suggest a reliable source for good quality Nano VNA's these days? Or similar pocket size VNA devices with PC support for downloading and analysis of data, preferably using Linux software.
There's a veritable jungle of shady Amazon vendors pushing crappy clones of clones of clones with questionable quality to say the least. Definitely monkey business! 🙈🙈🙈
Hey Michael, the NanoVNA-H4 from RandL.com is what I recommend to most hams...
@@TheSmokinApeThanks! 😃
I'll look into that one. 👍
This guy uses the coupling idea in this video ua-cam.com/video/2IqX0wyEXfU/v-deo.html
Thanks Keith, I will check that out 👍
Please pronounce "Fuchs-" like the "u" in "footage" and the "ch" in "fox". 😂
Foochs. Easy peasy.
I thought I did that 😂
Why use a vulgar expletive as click bait? Unsubscribing ...
Later bro, have fun watching the unboxers...
Who is this masked man Tonto ? Another Sad Ham, good riddance ! What drives these nonces ?
Wtf? What the frick? Doesn’t sound like an expletive to me.
🙄 Worldwide Toroid Foundation?
Lol@ toeroid foundation 👍
👍Thank you sir . sir your mail id please.
TheSmokinApe@gmail.com