Radio Room

Military radio and wireline communications equipment, and related stuff.

Feb 042012
 
MT-702/U Radio Mount

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.

…  Read More!

Jan 212012
 
T-368C On the Air!

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.

…  Read More!

Jan 072012
 
T-368C Firebottles

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.

…  Read More!

Jan 022012
 
T-368C Transmitter Progress!

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…

…  Read More!

Dec 312011
 
T-368C: First Smoke Test

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:

…  Read More!

Dec 172011
 
FT-505 Pack Mount for the SCR-619

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.

…  Read More!

Oct 052010
 
SRI-M550 Amplified Speaker

I bought this amplified communications speaker at a military surplus swap meet. It’s a nice little powered speaker which is intended for use with manpack radio sets (particularly ones with digital data capabilities). It is powered by a 9V battery which fits in a sealed compartment at the bottom of the unit. It is housed in a rugged aluminum chassis, and has a pair of clips on the back which can be used to hang the speaker from one of the “roll bar” handles which are common on these manpack sets.

 

…  Read More!

Mar 222009
 
KY-38 NESTOR Voice Encryption Device (Demilitarized)

 

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.

…  Read More!

Feb 192009
 
Message Book M-210


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.

…  Read More!

Nov 082007
 
TBY-4 Transceiver

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.

…  Read More!

May 292007
 
AN/TRC-179 "Regency Net" HF/SSB Transmitter/Receiver

The AN/TRC-179 Force Terminal is part of the “Regency Net” system, which was a radio system fielded in the 1980s. Regency Net was designed to survive the electro-magnetic pulse (EMP) from a nuclear airburst. Thus, its members are a lot more complicated than other radio systems with similar capabilities, with lots of filtering on all electrical inputs and outputs. The set covers 2.0000 to 29.9999 MHz with LSB, USB and data modes. The Regency Net members include a frequency-hopping Electronic Counter-Countermeasures (ECCM) mode. The sets can function in single-channel mode with the ECCM card removed, and they were often deployed this way to non-military users such as FEMA.

…  Read More!

May 252007
 
US Navy Microwave Protective Clothing

This conductive mesh suit was developed to protect people who need to work in strong RF fields emitted by Naval shipboard RADAR systems. It provides a minimum of 20dB of attenuation from 200 MHz to 10 GHz, in fields up to 200 mW/cm2. A complete set also includes rubber boots and gloves, a hardhat, and cotton over-clothes which prevent arcing between electrical equipment and the conductive mesh suit.

…  Read More!

May 242007
 

Instructions for Installation of Radio Sets AN/GRC-9 or SCR-694-C in Combination with Radio Sets AN/GRC-3 to 8, AN/VRQ-1 to 3, AN/VRC-8 to 10, AN/VRC-16 to 18, AN/PRC-8 to 10, or SCR-619 in Truck, 1/4 Ton, 4×4, Utility, M38 & M38A1 (Warning: 35 meg PDF file!)

 

Thanks go to Ken Perkins for the scans, and Wes Knettle for passing them along to me.

…  Read More!

May 032006
 
Chinese Type 102E HF Radio Set

I bought this Chinese HF transmitter/receiver set from seller redstarradio on eBay back around March, 2005. It came as a complete new set including the manuals, spares, tools, test equipment, etc. that would normally be issued with the set, all in original packaging. It was a lot of fun to unpack a brand new complete radio set in pristine condition! The historian in me felt bad about destroying the original packaging, but I just had to play with the radio! I compromised by carefully photographing everything as I unpacked it, paying special attention to packaging methods and markings.

…  Read More!

May 022006
 
Radar Set AN/PPS-6

Radar Set AN/PPS-6 is a lightweight non-coherent pulse Doppler combat surveillance radar operating in the X band between 9.0-9.5 GHz. When set up on its tripod, it allows the operator to detect moving objects at ranges of up to 1,500 meters (people) or 3000 meters (vehicles). The operator can measure the target range with a resolution of 50 meters. Transmitted RF power is generated by a magnetron tube, and the receiver local oscillator uses a klystron tube. It transmits pulses at a rate of about 2,000 pulses per second with a peak power of at least 100W and a width of 0.22-0.30 microseconds. An azimuth motor allows automatic scanning, and the motor may be disengaged for manual aiming. There is no display screen; the operator listens for the returned Doppler-shifted tone in the headphones, and reads out range on a mechanical counter after dialing in the range gate with a hand crank. The antenna is a 12 inch diameter truncated parabolic dish. The set operates either from an internal 12V silver-zinc rechargeable battery or an external 12VDC source.

…  Read More!

Nov 232005
 
S-448 Communications Shelter

I bought this S-448 communications shelter on 11/22/2005 from another military radio and vehicle collector. I plan to use it as my primary radio room at home. It originally housed a Collins AN/TSC-60(V)1 “Communication Central” set. The interior was completely stripped of equipment when the previous owner bought it, and he installed some equipment racks, desks, drawers, etc. He also re-wired it to run from single-phase power instead of three-phase power. The shelter would have originally had a panel on the right side of the door with a whole bunch of connectors and binding posts, but that has been replaced by a blank metal panel. If I need to add any external electrical connections, that would be the obvious place to do it. Some of the ventilation panels leak, but they look like they’ll be fairly easy to repair. Overall, the shelter is in good shape, and it’ll make a really nice radio shack.

…  Read More!