I just received this RU-19 aircraft radio receiving set from an eBay purchase. I plan to mate it up with my Westinghouse GP-7 transmitter. According to this chart of WW2 Navy radio gear, this particular combination would have been used in one of the Douglas SBD-3 Dauntless dive bomber configurations. I’ll also need to obtain an LM-7 frequency meter, DU-1 direction finder and various accessories to complete the set.
Military radio and wireline communications equipment, and related stuff.
I found this code practice oscillator on eBay, and purchased it out of curiosity. I haven’t seen one like it before. The only markings are “SER NO 1382″ engraved on the hinged cover, and a paper instruction label pasted inside the cover. The type of audio connectors used indicate that it was most likely made in the 1950s. It operates on 4 D-cells, with the oscillator potted in a green resin. The potted module appears to contain a piece of perfboard, and looks like it was cast in an ice cube tray. It is marked “CTI P/N AD183″. I haven’t managed to dig out audio accessories and batteries to test it yet… so many projects!
Have you seen an oscillator like this one before? Do you know when and where it might have been made? Do you have something interesting that you would like to trade for it?
I found this neat old telegraph sounder on eBay back in 2008. It appears to be British, and it is marked:
SOUNDER RELAYING TYPE B
I do not know much about it, other than it is clearly designed to provide both audible feedback and electrical switching. In other words, it’s a deliberately noisy relay which can both repeat an incoming telegraph signal and allow an operator to copy code by ear. It has a wooden base which appears to be intended for mounting on a wall, and it’s covered by a wooden lid with a glass window.
The TA-1042A/U is a member of the family of Digital Nonsecure Voice Terminals (DNVTs). Basically, this is a field telephone with a 4-wire digital interface to automatic telephone exchanges of the TRI-TAC family. The wireline interface can operate at either 16 or 32 kilobits per second. There is no embedded cryptographic capability, hence the term “nonsecure”.
Two TA-1042A/U field phones may be connected together with 4-wire field line (generally WF-16/U) and operated as plain field telephones, with power supplied by local batteries connected to the terminals on the right side of each phone. They may also be connected to a digital telephone exchange, and receive their power from the exchange over the 4-wire interface. They are not compatible with analog telephone lines, analog field phones, or civilian telephone exchanges. Earlier members of the DNVT family, such as the TA-954/TT, cannot be used without connection to a compatible telephone exchange (i.e., they can’t be used as simple field phones.
Chris Story K6RWJ and I have decided to take on a project to reverse-engineer the digital interface used by these telephones, and create an interface which will allow them to be used as VoIP phones. We have dubbed the project DNVT2IP.
I recently bought a Westinghouse GP-7 transmitter in the swap meet at this year’s annual West Coast Military Radio Collectors Group meeting, held in San Luis Obispo, CA at the beginning of May. This transmitter was made for use in Navy aircraft, and it requires 120 VAC 800 Hz power like other Navy radios of its era. Aircraft commonly use AC power at higher frequencies than our common 60 Hz “wall power” so that their transformers and motors can be lighter. The higher power frequencies allow transformers and motors to use less massive iron cores without magnetic saturation. 400 Hz power is now commonly used in large aircraft that require AC power supplies, but this transmitter was made before 400 Hz power became the standard. Unfortunately, it can’t simply be plugged into 60 Hz power. That would saturate the transformer cores, and then they would release their magic smoke and stop working.
Last weekend, the 18th annual meeting of the Military Radio Collectors Group was held in San Luis Obispo, California, at Camp San Luis Obispo’s NCO club. The event included equipment displays, presentations, field operations and a swap meet. I had a great time, and nearly every other comment I heard about this year’s meet was positive. I’m already looking forward to next year’s annual meeting, as well as the occasional field events we’ll probably have throughout the year.
The annual Military Radio Collectors Group meeting at Camp San Luis Obispo is almost here! This year, I’m pleased to announce that we’ll be conducting a joint crypto-related operation with the Maritime Radio Historical Society’s Coast Station KSM. Here’s their announcement of the operation.
Yesterday I was out at Fort MacArthur for an MRCG event. While I was there, I had a rare opportunity to ride in the fort’s half-track, complete with a quad .50 caliber antiaircraft gun in the back. I sat shotgun and operated the SCR-609 radio set. Some video may show up on YouTube someday. For now, here are a few pictures of the half-track.
Updated: Video of the event is embedded below.
For a long time, I’ve had a passing interest in radar antennas. Not so much the antennas themselves, but mostly their azimuth-elevation (az-el) drives. Every now and then, I’d search on eBay for any such az-el drives that looked both interesting and inexpensive, with or without antennas. I finally found one to buy about a month ago, and here’s a little bit about it.
I’ve just obtained a WW2-style packboard with an MT-702/U radio mount fastened to it. It’s similar to the FT-505 pack mount that I wrote about previously, and a BC-1335 transceiver will fit on it. However, unlike the FT-505 which has a wide spot for the BC-1335 and a narrow spot for a CH-191 battery box, this MT-702/U has two wide spots, each of which is the right size for a BC-1335.
I’m very happy to report that thanks to a NOS pair of Eimac 4-125A modulator tubes from Antique Electronic Supply, my T-368C is back on the air for the first time since I got it! I’ll still have plenty of tinkering to enjoy on it, and plenty of work integrating it into a full system with my R-390A receiver. I’m also happy that my antenna BALUN didn’t burst into flame upon encountering the hefty output of this small monster of a transmitter.
My T-368C transmitter uses three impressively large transmitting tubes. The power amplifier (PA) uses an Eimac 4-400A, while the modulator uses a pair of Eimac 4-125A tubes. These big tubes are beautiful in my opinion, especially when they’re operating with the plates glowing red. Sadly, they’re not normally visible in operation due to the transmitter’s opaque steel cabinet, studded with interlocks to keep folks away from the lethal high voltage that lurks inside. Even with the interlocks bypassed for debugging purposes (which is dangerous, and should be avoided when possible!), the big 4-400A tube is further obscured by an opaque metal chimney which ducts cooling air around it.
I’ve made some good progress on my T-368C transmitter already. The arcing problems have subsided on their own, though they may come back later. I traced down the modulator problem to a single resistor in the speech amplifier which failed open, thus removing power to the clipper tube’s plates and breaking the audio path. The transmitter is now working on CW and AM at full power into a dummy load! I also replaced another resistor in the same speech amplifier circuit, but I think it was actually OK and I just had a measurement error due to residual charge in the circuit.
There are still some kinks to work out…
I bought a T-368C HF transmitter project back in October, 2007 for $1575.42, and finally started seriously working on it a couple months or so ago. This evening, it got its first taste of power in many years! It’s semi-alive, but needs more work:
The SCR-619 radio set could be deployed in several different configurations, including vehicular and man-portable. In a man-portable configuration, the BC-1335 transceiver and CH-191 battery box would be installed on a common pack frame with an FT-505 mount. These mounts seem to be quite rare, as I’ve only found about two or three collectors who have them or have ever seen one for sale. A few months before the 2010 West Coast Military Radio Collector’s Group annual meeting, Paul Thekan kindly loaned me his FT-505 so that I could photograph it, measure it, and display it with my SCR-619 set at the meeting. I didn’t just photograph it, though… I also created a 3D CAD model of it, with thoughts of someday fabricating a reproduction.
The KY-38 is the manpack variant of the NESTOR family of voice security devices. Used during the Vietnam War, this family included the KY-8 vehicular unit, the KY-28 aircraft unit, and the KY-38 manpack unit. These devices permitted secure voice communications over radio.
This particular unit has been demilitarized; that is, all of the cryptographic hardware has been removed from the unit before it was released as surplus, leaving only the case, power supply, interface circuitry, and an interesting electromechanical keying device. The battery box is also missing.
Message Book M-210 was, as far as I have been able to determine, the standard form for recording message traffic during World War 2. A great deal of rigorous procedure was necessary to reliably route message traffic, and part of that procedure involved composing messages on the standardized carbon-copy forms in Message Book 210 prior to submission to message centers for routing. The same forms were used by message centers when transcribing messages (for example, after encrypting them with Converter M-209), when receiving messages sent via radio, etc.
I bought this TBY-4 transceiver in November, 2007 for the princely sum of $26. I plan to retore it to operation, and I’ll add more information about it here… someday. In the mean time, here are some pictures.