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THE AM BULLETIN BOARD => QSO => Topic started by: ka1tdq on August 21, 2021, 05:00:07 PM

Title: TBW-4 Military Transmitter
Post by: ka1tdq on August 21, 2021, 05:00:07 PM
I just got an old Navy transmitter that is in original condition and I just need to build a power supply for it. CW keying was accomplished through a relay built into the transmitter but I'm going to use that as the TX/RX switch and instead use solid state keying of the final cathode so that the relay isn't clacking away.

Anyway, here's some pictures before I cleaned it. I gave it a bath and it's drying now.

It'll go up to 18MHz, but I'm only interested in using it on the 80m slow speed military CW net. To my knowledge there isn't one off these on the air right now.


Title: Re: TBW-4 Military Transmitter
Post by: W1NB on August 21, 2021, 07:05:51 PM
Very cool looking transmitter.

Title: Re: TBW-4 Military Transmitter
Post by: WD5JKO on August 21, 2021, 08:05:49 PM


Is that an 803 used as a Final RF Amplifier?

Cool rig...


Title: Re: TBW-4 Military Transmitter
Post by: KA3EKH on August 21, 2021, 09:41:03 PM
A while back I built up a TBW transmitter and used it with a RAS (HRO) receiver. Did not do any CW but did a lot of AM on forty. The PA uses a 803 that’s suppressor modulated and sounded surprisingly good in AM considering the entire modulation chain was only one triode.
The original key system keyed the AC primaries and by using a high input frequency (800 cycles) they can get away with small filters but that renders all the filter components useless when building at 60 cycles.
A interesting foot note, they used a 800 cycle generator to power the transmitter and in A2 mode they introduced direct 800 cycle AC to the suppressor for modulated CW(A2).
Near as I can figure the TBW were built just for field use with no fixed shore version with that use falling to things like TDE and TDK with the TDE being a lot like the TBW only designed for shipboard or shore use at 60 cycles. A weird variant of the TBW is the GO transmitter that’s looks almost identical to the TBW but has no provision for A3, just A2 and A1 and was used in the early PBY Catalina flying boat. From what I have read the old GO transmitters were mostly yanked out and replaced by ART-13 transmitters being they were smaller, lighter and worked in voice mode.
You can see a video of my TBW at:

Title: Re: TBW-4 Military Transmitter
Post by: ka1tdq on August 22, 2021, 01:09:13 AM
After its bath, all fresh and clean! We'll start here.  ::)

Yes, the final is an 803.

That is an awesome video on your TBW! I don't have a power supply or control circuitry for mine so I'll need to build it. It's nice how they used letters on each knob so that the operator just had to go in sequence... A, B, C, etc.


Title: Re: TBW-4 Military Transmitter
Post by: kb3ouk on August 23, 2021, 07:06:43 PM
I have a GO-9 in the "get back on the air someday" line. Basically the same as what you have there with the TBW, just the HF unit, there was also a LF unit and power supply that all 3 cabinets would then mount together to form the complete transmitter. A complete GO-9 set is like 100 pounds, supposedly the biggest aircraft transmitter during WW2. Interesting tidbit about the TBW/GO-9, the front panels are mirror images of each other, every control and meter on your TBW is on the exact opposite side on my GO-9. The switch above the data tag is not original.

Title: Re: TBW-4 Military Transmitter
Post by: KA3EKH on August 24, 2021, 09:20:24 AM
The TBW and the GO series radios were a early war design, its hard to imagine that on the PBY Catalina flying boat they would have installed that huge radio with separate LF/HF transmitters and the relatively small RU-19 receiver that relied on changing plug in coils to change bands and all that stuff was CW only.
Figure that maybe because with the long-range reconnaissance function of the PBY they assumed it would only be able to communicate by CW and not AM and maybe that’s why they also included the LF section with its separate transmitter for communications with ships at sea?
The TBW originally came installed in huge water tight cases where the radio was hung in shock mounts inside the case and legs attached to the bottom of the case to allow the entire set up to be used in the field. Think the front of the case was used as a desk. A second case held two or three RBM receivers and that along with a heavy 800 cycle generator that powered the sets.
The TBW would be deployed at forward operating bases to provide communications and think it was accompanied by a crew of six men to support it.
At the end of WW2 tons of TBW sets were dumped on the surplus market and the first thing most Hams did was remove the water tight cases and dispose of them and build modern power supplies for operation from 60 cycles.  Being the original power supply was 800 cycles almost nothing except the plat current meter was useful and the LF transmitter had no use so very little of that stuff survived but the HF transmitter was relatively easy to get working so they got saved.
A lot of people in the military radio collecting community piss and moan about the Hams and how they hack everything and what a problem that is but the other side of that is if it were not for some Ham putting that radio aside with the idea of using it some day then it would have never survived this long and not be around today.

Title: Re: TBW-4 Military Transmitter
Post by: AJ1G on August 24, 2021, 01:57:47 PM
I recall reading in the book Ninety South which documented the establishment of our South Pole research station back in the 1950s, that early on in the  construction, a TBW transmitter was delivered as a major upgrade from what was being used up until that point to maintain radio contact with incoming and outgoing air traffic, McMurdo Sound Base, and points beyond.  Previously, they only had what was described as a small portable HF field set.  A specific model was not noted, but most likely was an AN/GRC-9.  I was surprised that a TBW was being deployed in the 1950s. No doubt the TBW was replaced by more modern equipment that was coming along that was SSB capable.  Glenn, N1SNG recently told me that their primary stateside station they handled traffic through was located at Quonset Point Rhode Island, which used a large rhombic pointing due south.  The main SeaBee base on the East Coast was located in the vicinity of QP at Davisville.

There are a number operators here on the East Coast that from time to time bring up their TBWs on the Old Military CW Radio Net at 2100 Eastern Time on Sunday nights.  The net which used to operate on 3570 kHz for several decades, now meets on 3558 kHz due to the heavy digital activity on and adjacent to 3570. 
When the nights get longer and static levels drop, we’d love to have a West Coast TBW drop in.

Title: Re: TBW-4 Military Transmitter
Post by: KA3EKH on August 24, 2021, 04:11:32 PM
The TBW in its native form:

Think that maybe that set with the big antenna and generator would be the largest set of radios that the Navy fielded for a while for portable “field” operation and know from experience that it was well capable of developing over one hundred watts with ease in CW, think I only ran about 75 or 80 watts AM with the one I had but until you get into the real big transmitters that were not intended to be easily transported the TBW may have been king. The Army had the BC-610 and SCR-299 sets but don’t think the Navy ever used that stuff being it was Army.

Title: Re: TBW-4 Military Transmitter
Post by: Opcom on August 27, 2021, 03:03:10 AM
Great find! I can't think of anyone who could treat it better.

Title: Re: TBW-4 Military Transmitter
Post by: k3msb on August 27, 2021, 02:36:18 PM
I currently have a TBW-5 on the air and have just obtained a TBW-4 and Rectifier Modulator unit.

Let me know if I can help you out.

Title: Re: TBW-4 Military Transmitter
Post by: AB5S on August 28, 2021, 03:39:05 PM
Hi, Mark.
Nice looking TBW-5.  I've forgotten how you modulate it.
I got my GO-9 (aircraft TBW) cathode-modulated, but considering other things.
It came with a near-intact HF Transmitter, but a completely stripped power supply.
Good excuse for building a 60 cycle AC supply.

I used grid-block keying, which was easy as pie, but scares the heck out of
some folks because it's switched straight off the AC line (I have a "correct AC socket
wiring" tester integral with the rig).  Provides -160 VDC to transmitter pin 17, which
cuts everything off nicely during key-up.  Don't know why some folks balk, as they
commonly have like 300 VDC on the switch contacts of the mike they hold, LOL.

GL OM ES 73 DE Dave AB5S
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands