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Abbott Instrument TR-4B




 
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W9GT
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« on: October 27, 2017, 10:13:17 AM »

I brought home a neat little treasure from a hamfest this weekend.  Its an Abbott Instrument TR-4B 2 Meter AM Transceiver from the 1940's.  These units, in an earlier form (TR-4), were produced and used during WWII for the W.E.R.S. War Emergency Radio Service.  They were originally on the old 2 1/2 meter band and then the later units produced after the war, were built to cover the 2 meter band.  They contain a super regen receiver using a 955 acorn tube and an HY-75 tube modulated oscillator for the transmitter.  Also a 6L6 modulator and audio output with a 7F7 for the first audio stage.  Its a neat little package that is very well constructed.  I wouldn't try using the transmitter as-is for obvious reasons, but the receiver should be easy to get going.

If you want to see a picture and ad for this rig, there is a full page ad in the advertising section of the 1944 ARRL handbook on page 104.

Does anyone have a manual or schematic for this rig?  I would like to get it going, at least on the receive side.


73,  Jack, W9GT


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73, Jack, W9GT
WB6NVH
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« Reply #1 on: October 29, 2017, 02:11:12 AM »

I have a straight TR-4 and also a DK-3.  The consensus seems to be that manuals were never written in terms of a schematic being available, although there must have been an instruction sheet of some sort.  It will be interesting to see if anyone turns something up.
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Geoff Fors
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« Reply #2 on: October 29, 2017, 11:42:43 AM »

What a terrific find! This brings back great memories for me. In 1950, the year I got my ticket, W3DQE used to take me along in his Plymouth on transmitter hunts, using a TR-4A and cubical quad rotatable beam on a broom stick mast mounted on the running board. To the consternation of other participants using comparatively sophisticated receivers and "secret" antennas, Ed had an uncanny way of juggling antenna coupling and superregen threshold on that TR-4 rush box, using noise level variations to peak the hidden Tx, where we often arrived well before the wise guys from across the river at RCA with their superhets and 4" S-meters. What a hoot, and a great testimonial for what the TR-4 could do in the "modern" world.

Later that year, when I got on 2M, I built a copy of the Abbott 5-element beam, another product of that pioneering company, that worked well with a converted SCR-522.

Jack, I hope you can get your historic transceiver -- at least its receiver -- working. One thing for sure, you will be able to listen to at least two repeaters at once!

Bob - NE

   
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W9GT
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« Reply #3 on: October 29, 2017, 07:42:33 PM »

Well, I traced the circuitry enough to figure out the power requirements and built a power supply for the TR-4B.  I should have the interconnecting cable completed tomorrow and I will see if she will fire up.  Wish me luck!

73,  Jack, W9GT
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« Reply #4 on: October 30, 2017, 06:19:59 PM »

Built the power supply and hooked it up.  It works fine!  Had to recap and also replaced a couple of 100K resistors in the rig that had increased in value.  The regen receiver seems pretty sensitive, but it is very touchy to set the coupling and regen correctly.  I was able to hear a couple of local repeaters OK with only a clip-lead antenna.  The transmitter operates, but I did not attempt putting it on the air as modulated oscillators are a no-no.  Fun project, interesting rig that was saved from the junk pile.  If you have one of these rigs, I can provide the info for the power supply.  I used a tube rectifier just for a period-correct arrangement, but I cheated with some solid state diodes under the chassis for the bias supply.

73,  Jack, W9GT


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73, Jack, W9GT
Todd, KA1KAQ
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« Reply #5 on: October 31, 2017, 12:06:00 PM »

I actually have the power supply and accessories with mine Jack, but before I could find it you figured it all out! Someone posted about this transmitter a couple years back and I can't recall if I posted the documentation then. If not, I'll scan and post it once it surfaces again. It's in the basement somewhere. Also have one of the DK models, a 2.

The power supply actually has a holder for a couple of D-cell batteries.


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known as The Voice of Vermont in a previous life
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« Reply #6 on: October 31, 2017, 12:26:23 PM »

Nice period-looking P.S. Jack.  Glad you had some success with the receiver but your difficulty adjusting regeneration reminds me that antenna coupling had a lot to do with optimizing receive performance on W3DQE's mobile rig. Also, those snazzy polystyrene-insulated balanced antenna posts were necessary because most hams didn't have coax until after the war, so open wire line (or a-c zip cord!) was used before and during the war, then 300-ohm twin lead was developed for TV antennas and was widely used by hams until coax became widely available. Thanks for the update.

Bob - NE
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W9GT
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« Reply #7 on: October 31, 2017, 04:54:50 PM »

I actually have the power supply and accessories with mine Jack, but before I could find it you figured it all out! Someone posted about this transmitter a couple years back and I can't recall if I posted the documentation then. If not, I'll scan and post it once it surfaces again. It's in the basement somewhere. Also have one of the DK models, a 2.

The power supply actually has a holder for a couple of D-cell batteries.

That's cool Todd!  Well I guess they were only using 3 volts for bias and , perhaps carbon mike voltage.  I read somewhere that -22 V was needed, so I built that into the supply.  Varying the bias has little or no effect on the operation of the receiver.

73,  Jack, W9GT
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Tubes and Black Wrinkle Rule!!
73, Jack, W9GT
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