Radio Room

Military radio and wireline communications equipment, and related stuff.

Apr 082020
AN/TGC-14A(V) Mite Teletypewriter

I got this AN/TGC-14A(V) Mite Teletypewriter at the 2019 Military Radio Collectors Group meeting. One of these days, I plan to mate it up with an AN/PRC-47 transceiver and CV-2455 converter to make an RTTY set like Dave Ross N7EPI (SK) used to operate at MRCG events. I think that his Mite was one of the rare as hen’s teeth models that was configured to be powered by 28 VDC. Mine is configured to be powered by 115 VAC 400 Hz, which is going to be a lot less convenient to produce… but at least it’ll be a power source which can also directly power the AN/PRC-47 set.

This Mite has a single external 12-pin connector. I believe that its connector is Amphenol part number 165-11, and the mating connector for it would be Amphenol part number 165-10. I don’t have any cables or mating connectors for it yet, and I don’t know if it works yet, either.

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Feb 112018
What's This HF Digital Mode? (Spoiler: It's FT8)

At the moment, I’m hearing a whole bunch of traffic around 14.074 MHz in a digital mode that I don’t recognize. I haven’t been able to get intelligible text out of fldigi from this yet. From the amount of traffic, I wonder if this might be some sort of contest activity. Can anybody provide a hint about what this mode is?

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Nov 062016
Canadian CRT-1/CPRC-26 Radio

I found this 1950s-era Canadian military radio in an online Goodwill auction, of all places. It is missing its whip antenna, but a friend in Australia is helping me out with that. This one may be tricky to repair if it doesn’t already work, because all but one of the vacuum tubes are hermetically sealed into individual metal cans. The modular construction made these easy to repair in service, but I don’t have a stock of spare modules to draw from. Updated 2020-09-15: Added manual scans.

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Nov 052016
My First Teletype Model 28

Thanks to David Reid W6KL, I now have my first Teletype Model 28! I’ve had a number of Teletype Model 33 machines over the years, but this is my first 28. I’ve always been impressed with the 28 machines I’ve encountered at Military Radio Collectors Group meets, so I’m happy to finally add one to my collection. This one was owned by Al Tipsword W6GER (SK) before David adopted it.

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Dec 202015
Another KY-38 NESTOR Voice Encryption Device (Demilitarized)

Back in 2009, I posted about a demilitarized KY-38 NESTOR voice encryption device. Since then, I’ve procured another one. Like the first one, it has been demilitarized (that is, rendered inoperable and unclassified) by removal of key internal components, removal of the original dataplate, and (for some reason I don’t understand) removal of the battery box. But unlike the first one, this one came with a 28″ cable to plug it into the AN/PRC-77 radio, and a matching transit case! There was even an old trouble ticket lost under the padding, though it was for a different unit based on the serial number.

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Nov 292014
pyMiniCircuits: Python Support for Mini-Circuits Portable Test Equipment

Well, that didn’t take long. As mentioned in my previous post, I’ve just created a Python package providing support for Mini-Circuits brand portable test equipment. Well, more accurately, it just provides support for my model PWR-SEN-4GHS USB-interfaced RF power sensor (and probably the other sensors in that product line), since that’s the only piece of Mini-Circuits test gear that I have.

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Jul 132014
Chalco Paper Tape Reader

I just bought this punched paper tape reader through eBay, just because it looks neat. It was made by Chalco Engineering Corporation, and the accompanying paperwork indicates that it was part of the AN/TPN-19 radar system. It appears to have been overhauled and then packed up for use as a spare. I didn’t find any technical details about it online, but to my amazement I found an original manual for this series of tape readers in another eBay listing! The manual doesn’t cover all of the details of this particular model, but it should be very helpful anyway. When I get around to it, I’ll scan the manual so it can be archived online somewhere.

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Jul 272013
RU-19 Aircraft Radio Receiving Set

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.

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Jun 162013
Code Practice Oscillator

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?

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Jun 112013
British Telegraph Sounder

I found this neat old telegraph sounder on eBay back in 2008. It appears to be British, and it is marked:


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.

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May 302013
TA-1042A/U Digital Nonsecure Voice Terminal (DNVT)

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.

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May 122013
800 Hz Power for Navy Radios, Part 1

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.

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May 082013
2013 MRCG Event After-Action Report

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.

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