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SCORE! @ Ballston Spa NY hamfest...




 
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Author Topic: SCORE! @ Ballston Spa NY hamfest...  (Read 653 times)
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WBear2GCR
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« on: September 10, 2017, 08:42:51 PM »

The Ballston Spa NY hamfest is a small-ish hamfest, not totally small though... this year
not many sellers, but it was well attended.

Anyhow, getting out of my car, I walked into one of the sheds (fairgrounds, you know?). The third table in I spied two grey, low slung rack units stacked. Closer examination revealed the object of much online reading lust, for this op.

I had come just to find a decent price on a "25amp" DC supply for basic solid state rigs,some connectors,
maybe some other odds-n-endz. Then, this!

After some negotiation, the larger, lower unit had changed hands, and was gleefully carried to my waiting
horse drawn buggy. Oh, no, it was my car. Sorry. Cheesy

Later I went back and for too much money bought the other smaller unit. Aka "the exciter".

The exciter does CW or AM at a whopping 1 watt.
Whatcha gonna do with a 1 watt exciter, sonny?  Roll Eyes

Those who are "in the know" will know... Cheesy

Found my PS, connectors and a few other odds-n-endz too.
AND, a small (16" dia?) horn suitable for use as an "outside speaker".
Now, I just need the windchimes.
Oddly enough, two DX-100s recently showed up. Hmmm... should I be worried??

Happy bear! Cheesy




* TMC PAL 350 AMP.jpg (379.26 KB, 1480x1110 - viewed 125 times.)

* TMC PAL 350 TOP.JPG (480.54 KB, 1480x1973 - viewed 98 times.)

* TMC GPR EXCITER for PAL350.JPG (364.16 KB, 1480x1110 - viewed 97 times.)
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KC4VWU
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« Reply #1 on: September 11, 2017, 01:25:57 AM »

Oh man, just saw this! You're gonna love that setup! Did you get the supply too? K4OZY has all the dope on this at his website. He's the "go to" on TMC stuff.
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WBear2GCR
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« Reply #2 on: September 11, 2017, 08:46:34 AM »

No Power supply... could be an issue.
First the oddball power connector.

Then looking at the schematic, there are some control relays that duplicating will be a RPIA (Royal Pain In the Arse).

Then too the power out is a bit anemic, the redeeming factor is the super low IMD.
My Valiant pretty much will strap the TMC in AM... Sad

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KC4VWU
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« Reply #3 on: September 11, 2017, 11:22:04 AM »

Yes, not a powerhouse at 100w and pretty heavy at that, but the quality!

The exciter is the really nice thing. You could build a PA that would suit your power requirements. Russian external anode tubes are plentiful (for now) and a wide variety to choose from. The microphone connector could possibly be tough to locate, but I believe all it's functions parallel to the terminal strip on the rear. IIRC, the exciter will do up to 10w stand alone?

Another source on these is Bob Sullivan K0YVA. His web site details some resto work on some TMC gear. Mark Francis, KI0PF, has a lot of info in his book, Mil Spec Radio Gear Vol.1, and if you don't have a copy, get one. Amazon is the place to find it, and I believe Ray at ER has them also.

Lots of inquisitive QSO's when you tell them your transmitter is a TMC!
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W1ITT
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« Reply #4 on: September 11, 2017, 01:51:04 PM »

You mention that the TMC amp has "super low IMD".  Eimac's Care and Feeding of Power Grid Tubes lists the 4cx250B as having -25 db IMD.  That's awful !  Even the typical solid state ricebox will do -30 db or so.  Is TMC employing some sort of feedback to clean their amp up?
The 4cx350J is a cat of a different stripe.  Those tubes could run IMD better than -40 db.
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WBear2GCR
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« Reply #5 on: September 11, 2017, 05:51:40 PM »

Yes feedback.

The manual is at http://www.tmchistory.org/

I think the larger amp uses a PL-172(?) is spec'd @-50dB IMD.
Better tube I guess?

I was mostly interested in it because I had been trying to research how feedback in RF amplifiers
is handled, and found next to nothing on the subject!!

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WBear2GCR
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« Reply #6 on: September 11, 2017, 05:58:06 PM »

Yes, not a powerhouse at 100w and pretty heavy at that, but the quality!

The exciter is the really nice thing. You could build a PA that would suit your power requirements. Russian external anode tubes are plentiful (for now) and a wide variety to choose from. The microphone connector could possibly be tough to locate, but I believe all it's functions parallel to the terminal strip on the rear. IIRC, the exciter will do up to 10w stand alone?

I'd be surprised if it did 10watts. Have yet to download that manual.

The mic connector, oddly enough, appears to be a standard DIN plug! (ick!!!)
I have very limited interest in the exciter, EXCEPT to the extent that it mates perfectly with the amp.
Which makes it easier (in theory) to get the amp running...

Quote
Another source on these is Bob Sullivan K0YVA. His web site details some resto work on some TMC gear. Mark Francis, KI0PF, has a lot of info in his book, Mil Spec Radio Gear Vol.1, and if you don't have a copy, get one. Amazon is the place to find it, and I believe Ray at ER has them also.

Lots of inquisitive QSO's when you tell them your transmitter is a TMC!

Thanks for the leads.
Personally I'm less interested in the brand, than in the circuit! Cheesy
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W1RC
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« Reply #7 on: September 11, 2017, 06:32:57 PM »

I am familiar with the PAL 500 Amplifier.  Many were built in Ottawa Ontario in the Fifties for use on the DEW Line.  The agreement between the US and Canadian government stipulated that the equipment had to be made in Canada.  This is why Collins Radio opened a factory in Toronto.

William Ford, a surplus dealer in Smiths Falls Ontario had stacks of these back in the 80s.  I don't know if he is still in business (probably not) but it is a lead you might want to track down........

The fellow that sold them to you was at Boxborough MA on Saturday and had these two,pieces on his table.  There were no takers.  

Good luck finding the connector.  

73,

MrMike
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WBear2GCR
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« Reply #8 on: September 12, 2017, 08:19:59 AM »


That was Bob, N2OAM...   
I'd rather have the PAL500, but whatever...
Either I will find the connector, or I will make it work!  Grin

That plug module can be replaced and something with discrete HV & LV put in the same space.

Thanks for the lead on the guy in Canada... I'm not going to pay as much for the connector
as a high % of what I paid for the unit!! Heh.
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WBear2GCR
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« Reply #9 on: September 12, 2017, 09:24:36 AM »


www.repairfaq.org/ELE/F_surplus_ca.htm shows Ford as closed as of 2008. Sad

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VA3AEX
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« Reply #10 on: September 15, 2017, 08:49:05 AM »

William Ford had a huge warehouse in little Smith Falls Ontario, and when I went in to look for my first BA receiver in 2006, he had at least one of each of the entire line up of Hammarlund Receivers for sale. After talking to him about which rig he recommended, I ended up going home with an Hammarlund HQ180.  Loved that receiver notwithstanding its restricted audio, but it was perfectly suited for high noise suburban environment.
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KD6VXI
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« Reply #11 on: September 15, 2017, 09:27:47 AM »

Is that the surplus dealer in Canada that had problems delivering what he promised, delivered broken stuff, didn't deliver, etc?

--Shane
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KC4VWU
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« Reply #12 on: September 15, 2017, 09:48:03 AM »

Yes, I was way off at  10w out. The manual says way less than a watt. Haven't messed with the setup in better than 5 years.

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w1vtp
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« Reply #13 on: September 15, 2017, 05:41:12 PM »

Bear

I'd be most interested in how they got to that 300 watt power level unless it was an experimentally derived power limit to keep the IMD down. Any under driven linear should put out lower IMD it they are proper loaded.  The manual does say that the amp operates in AB1 mode so I'm really puzzled.  Perhaps if you were to bypass the driver circuit and drive the amp directly, that would bypass the load and drive protection circuitry and allow you to run that amp at its full potential.  Given the two 4CX250b's running at 2000 V @ 500 MA, you should be able to run that amp with about 600 - 700 watts PEP on SSB.  AM? well, you would be limited to about 60 watts carrier @ 125% positive peaks.  Way less than your Valient II but - this is a "science project" right?

There are two commercial rigs that use 4CX250b's successfully: the Eldico SSB-1000 and the Collins KWS-1 put the output at more than TWICE the PEP of this transmitter.  I've included the spec page from the ELDICO SSB-1000 which in my opinion is a very well designed linear, second only to the KWS-1 linear which has some additional refinements.

Finally: just get rid of that odd connector and go with a barrier strip with the infamous Millen HV connector and be done with it.

GL es keep us apprised, Al

* ELDICO_ssb1000 (PG5).pdf (469.04 KB - downloaded 17 times.)
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WBear2GCR
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« Reply #14 on: September 22, 2017, 06:03:45 PM »

Since my earlier post, I had the opportunity to correspond briefly with a Canadian ham who had had a PAL 500.

He commented that if he tried to load it beyond the "spec" the protection/overload would trip the linear OFF.

So, this leads me to believe that they have it rigged, possibly because of IMD spec, and possibly to maximize tube
life and reliability... likely this explains the multi-pole relays in the PS deck. I did not have time to review the manual
between then and now, but I speculate that if I build a homebrew PS, that this feature would be obviated, and
mo' powah out would thenceforth emanate! Cheesy If desired.

At some point I will print out the PAL 350 and 500 sketch-a-matics and sit down and have a look-see at what they
actually did.

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« Reply #15 on: September 23, 2017, 11:32:58 AM »

A single 250B will do 500 pep without breaking a sweat.

I've got an unusually hot 250 here that does nearly a kilowatt pep out before it saturates

IMD is NOT at friendly levels at these outputs however.

--Shane
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« Reply #16 on: Yesterday at 09:45:30 AM »

I'd be most interested in how they got to that 300 watt power level unless it was an experimentally derived power limit to keep the IMD down.

Low IMD was a PRIMARY goal of TMC's line of transmitters - their main application was for ISB multi-channel RTTY (VFCT) where up to 16 or 32 FSK signals were frequency multiplexed in each sideband. A typical TMC exciter puts out 500mw from a Class A 6146 with 6kc audio bandwidth for each sideband. Typical transmission is both sidebands plus carrier insertion at 40-50 dB down. The reduced carrier is used at the receiving end for AFC (with 85cps shift and 170cps channel spacing you better not drift too much).

TMC gear was also used for voice SSB, of course, often with voice on USB and FSK on LSB simultaneously.

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