How to Connect a Modern Radio to a Legacy Tube Amp (
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- Опубліковано 1 сер 2024
- Ron, W8NIM, asks about connecting a Yaesu FTDX1200 to a legacy Ameritron 811H 800 watt tube-based amplifier. We look at how amps are generally connected to radios and then examine his specific situation and ways to overcome it.
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...and yet, another real world example expertly demonstrated!
"Thanks Dave."
I get excited when using my new 811H amp. First time ever had one. Got it in September. Was easy to hook up to my old ICOM 751. Make sure to connect a Watt meter that is what you need to tune the am up. Also I tune up into a dummy load. I use an MFJ 267. My 811H came with a grid protection circuit that will switch the amp to stand by if too much grid current drive is applied. It sure does protect the tubes. I do not use the ALC connection.
Thanks Dave for the information!
I don’t have an amp but still enjoyed the information & explanation.
Very helpful, thanks Dave.
Great video Dave...remember building my first HEATHKIT Solid state final amp 30 years ago..wish I hadn't sold it..wish Heathkit was still around...
Paul K1YOU
Operate/Standby Switch does NOT turn the filament off.
Thank you.
Hmmm...
As is typical, mfj seems to go the long & expensive way to do a simple interface.
Ok folks, this is basic Ohm's Law & voltage divider stuff!
The ALC OUTPUT of the amp is 0 to -12 volts.
We want 0 to -4 volts.
That's a 3 to 1 ratio... (12/4)
If we were to put 12 x 1k Ohm resistors in series (12k total) across that ALC output, that would provide a 1 milliamp current flow. Just right.
Now tap the ground & the top of the 4th resistor & you have a perfect 0 to -4 volt drive TO the radio! Now of course if you could find a 1% 4k & an 8k, that would be easier; though those are not easy to find, so go grab 6 x 2k Ohm 1% 1/2 Watt resistors & a small perfboard & solder them up. By the way, still a 3 to 1 ratio! Tap in your wire & test.
Literally around a buck in parts! Not $70 to $100.
73
With PTT, be _very_ careful about the voltage used. Older linears often used relays with full mains voltage (125V) coils.
Most of those radio mini-DINs are on a 0.1" spacing so vero board, #18 tinned brass wire, a relay and couple of resistors with hot melt glue do the trick. I did that on IC-706 to SB200, and waiting on round tuits for FT-950 to AM-811
With tube amps, you normally would not want to switch the filaments on and off -- as the associated temperature changes greatly shorten the life of the filaments and thus the tubes.
From the 811H manual ... "Operate/Standby Switch: Used to remove the amplifier from the RF line while filament and plate voltages are maintained during 'barefoot' operation."
So what, you keep the amp on standby forever, day in and day out, year after year?
Could you talk about the delay you can set in the ICOM 7300 radio and other when using an AMP.
This has been a very helpful video for me, as I have an old Collins 30L-1 and want to try it out. My hf rig is an icom 7300 and the alc voltage in not in the manual for the collins. I also have an old ft101zd with tubes in the final and that is circa the same generation as the collins (almost.) So I have some thinkin to do. thanks again. Bill VE3MRX
Could one use 7 or 8 diodes in series on the ALC connection to drop the control voltage?
Great Videos Dave.
Is it ok to key the Amplifier with a foot switch?
73
Hi Dave, how would you hook up an AmpKeyer made by Sunlight Energy Systems to you IC-7300 and and a Heath SB-200?
Good presentation. Enjoyed. But my comment to you is ... It is pleasant to see you looking more healthy!
Thank you!
I have Yaesu Ftdx10 and Ameritron ALS-600. Please suggest cable type and brand for connection with ALS-600, ARB-704 and FTdx10. Thank you
I have the 811H from an SK and want to connect to the 7300. The 811H manual predates the 7300 so connections are a mystery. What do you recommend for the keying and ALC connectors? 7300 manual shows RCA socket for each as does the 811H. Also, how can I tell if the 811H has had the 12/10m mod installed? Tks 73/K7SXN
I have the 811h amp with IC7300. I've blown the 7300 finals twice. I'm puzzled as the 811h has an ALC adjustment with NO information for it's use. I do have the ALC cable connected. Is it possible the issue of blown final could be ALC adjustment,? Tks. K7SXN
I recently did this. Picked up a used 811 then purchased a Yaesu FTDX-101D. Had to solder up a couple connectors but managed to figure it out. I really could have used your video about four weeks ago. This was a good project for me since I am relatively new. Been able to work some nice DX though. I'm thinking about putting some 572b tubes in this unit. Perhaps you can show us how to figure the difference between the the 811 and 572 tubes? Plate and grid numbers should be different. Thanks for the videos and the continued education. Tim W4TLA
Hi Tim. each 811A has 65 watts plate dissipation which ads up to 265 watts dissipation if 4 tubes. 572B's have 160 watts each adding to 640 watts of plate dissipation so they should run cooler than the 811A's Remember that there is only so much power supply current available so if you do that treat the 572b's as if they are 811A's. Hope this helps, Look at the AL572B amp which uses 4 572B's and see the differences. OJ KØOJ
To interface modern rig to older amps, it is a good idea to use and interface for ground/ key current problems in keying it. The Ameritron / MFJ ARB-704 is excellent.
In ALL cases, be sure you know the maximum input power the amp manufacturer lists - there are many that will overload and heavily distort if more than 20, or 30 or 40 etc. watts are fed into the input. Not many it seems will take the actual 100 watts input.
Or just use a transistor and a few resistors for the keying protection. Reading the manual about max input power is always a must
Hello David,
If we make a resistive divider for the ALC, assuming the current to the radio is small, example: R1=100 Ohm + R2=51 Ohm, and take the out for radio at R2, I=12V/151=80mA, R2(51)*0.08~4V R1,2 1W
What do You think about it?
I love Yours videos. Thanks and best 73s
I use a foot switch to key the amplifier leaving the ALC lead out just keep power at 65 watts or a bit lower it works and stops the magic smoke coming out of the radio and amp.
Look for the ALC level control on the rear of the 811h
I have an old Ameritron ALS-500M and a XIEGU G90 HF RADIO, I was worried about the higher voltages and current, needed by the keying circuit of the AMP and the low voltages in the XIEGU, so I bought a MFJ RF sense rec/xmit switch (I also use it for my SDR receiver). The MFJ unit detects the RF from the transmitter and sinks the 12 volts of the AMP to ground, thus keying the AMP.
My G90 HF RADIO puts out 20 watts and I get 300+ from the AMP.
PNP-10MY cable to connect ARB-704 to newer Yaesu rigs is NOT available from Ameritron as of 2/1/23 (when I checked). They are depending on a Chinese source and could not give me an availability date. None of the outlets have them in stock.
Hope to see a video on using an amp with the 7300. My dad has an old homebrew tube amp my grandpa made and I'd like to run it on the 7300 but don't want t damage my radio out of ignorance.
You'll need an amplifier keying interface. It's purpose is to reduce the 120v (or 240v depending on your location) relay keying voltage to 12v or less. This will prevent damage to your 7300. The other option is using a foot switch to key the amp first, THEN key your transmitter. After talking, release the transmitter then release the foot key. Remember, there's AC voltage on the amplifier keying plug, usually an RCA jack.
@@MoparMasters Thanks for the reply. I have been reading about it and have seen recommendations to add a qsk box is this what your referring to?
@@420bakersarmy not all QSK boards are "soft key". Look for a Keying Interface instead.
Why can’t a manual tell me this? You made it sound much simpler than they do.
Thanks Dave!
Unused to hearing them called "Amplifiers." In earlier days, we always called them "LINEARS." (Of course, I KNOW that technically the category is "LINEAR amplifier!" P.S. The term is actually seen in the Yaesu manual @ 10:37 in this video.)
Don't depend on the ARB-704 with a Collins 30L1, it says it will work but the 30L1 has -170V on key circuit. 704 is rated at 200v, but the 30L1 killed mine last night, and I've seen similar results from others online.
You can build your own with a relay module board if you are have a bit of electronics ability.
Good job! TNX.
Not a good idea to drive amps at max power. Only drive hard enough for good communications.
On the ARB-704, the ALC connection is just a thru connection. It will not change the -12VDC supplied by the amp to -4VDC! For that you need to use a pot in series to manually adjust ALC voltage, or better, use some op amp circuit to turn it down! If you connect to the ARB-704 ALC, you are simply transferring the -12V to the exciter and will damage your radio. MFJ does explain that in the fine print. Best not to use ALC.
I'm dying to get an amp! I hear so many stations but when I try to reach out it's like I'm screaming into the void.
I like youtube very much thank you
Couldn't a simple divider circuit be used to make the ALC voltage one third of what it is coming out of the amplifier? Thanks Dave!
Not sure. Would depend on the impedances involved. If the 1200's input circuit had very little impedance (meaning high impedance) then yes, it would work.
The AL-811H actually has the voltage divider built-in! The adjustment is on the back of the unit, and can scale the ALC Output down to whatever level is required.
Good luck!
73
Tony KB9A
@@davecasler Confusing answer Dave. Here's my take. If you think about it it is not the amp that should be high impedance but rather the exciter ALC input.
Let's say we want to measure a voltage, which in essence is what the exciter is doing.
To measure the voltage accurately, the source voltage should not be influenced by any load from the voltmeter i.e. the voltmeter needs to be much higher impedance than the source. This is why modern digital voltmeters like the typical DMM are more accurate than the older passive analogue meters. A modern DMM will usually have an input impedance in the range of 10's of Mohm or more while passive analogue meters usually run around 10 - 50 Kohm.
So in answer to Gwnii69. Yes a resistive voltage divider is suitable with the caveat the divider itself also needs to be high impedance to minimise voltage drop from the ALC source but not so resistive so as to swamp the exciter ALC input impedance.
One other thing I would comment on, the 811H might be considered an intermediate unit in evolutionary terms and as you correctly point out the 811H T/R relay switching requirements are compatible with most modern HF radios of 12V. and sub 1amp However older generations of amp may supply 80V or more to activate the T/R relay. Clearly modern rig breaking voltages.
Question. ...what are you saying in the intro? Hello "augiees"?? worldwide.
I would love to hear some advice on ham radio's "no go zones". Being an ignorant new ham I was unfortunate enough to tune across the apparently notorious "7.200" on 40. Wow, I don't know how the FCC hasn't shut these guys down. Constant profanity, playing music and failures to ID. Anyone unfamiliar with this just need search "7200 ham" here on UA-cam.
It's worth noting that outside of region 2 the 40m band stops as 7.200 anyway so anything transmitted above that is essentially inter North America only
that's the national tuning frequency in case you don't have a dummy load
I am surprised Ameritron didn't use a 4CX500 with forced air cooling instead of use glass vacuum tubes.
MFJ's instruction manuals in general are confusing to beginners.
DO NOT DO WHAT I DID ONE TIME - Make sure you DO NOT get the Keying line and the ALC lines REVERSED - On older rigs, they are usually BOTH RCA jacks. This will terminate your transceiver's existence. I now clearly view the back of both units when connecting these (or I don't connect the ALC line at all).
That looks like an Yeasu FL2100b amplifier diagram.
Actually, there really isn't much variation on the basic circuit. The amplifer core is simple, but lots of complicated protections and measurements can be built around it. The amp shown in the video is MFJ.
@@davecasler looks exactly like my Yeasu FL-2100b manual drawing. I do own the amplifier.
It would be nice to explain how to build simple amp-transceiver interface rather than advertising $65 commercial device.
So many errors...I cant keep watching...
wheres your video?
Boring
A lot of misinformation, in this video, concerning amplifier circuitry and function of controls.