Racal TRA 55 B

[crackle]

Hi
Please can anyone help with information on this piece of equipment.
Year; where it was used; service information. Anything else of interest.







Thanks
Mike

[PeterRoberts]

Hi Mike,

Never seen or heard of these before, but there are a few hits on the web. It seems to be late 1950's and is based on the RCA SSB-1 transceiver. More info here.
One early user seems to be the Rhodesia & Nyasaland Corp of Signals (RN Sigs) according to an article on SSB manpacks in Africa here.

Peter
G4DJB

[trh01uk]

Very interesting to see early examples of a new technology hitting the streets. The WW article Peter has referenced above is dated May 1958. The UK military at the time were just adopting the latest in AM/CW technology for HF use - with some use of FM/PM too - in the form of various Larkspur sets that came out in the 1955 to 1960-ish period. Not a sniff of SSB there!

According to this article, commercial SSB rigs for amateurs only arrived in the early 60s, though home-constructed rigs for experimental purposes started long before that - definitely immediately post-WWII, and according to the same article in the 1930s by some US-based amateurs.

Incidentally to answer the OP's question, I'm afraid I've got no info either. But I hope someone turns something up - as I will be interested to see it too.

Richard


Richard

[Radio Wrangler]

SSB dates back to the 1920s in the USA where Bell labs were working on ways of getting more than one signal down each long distance phone line. It turned into the FDM that did all the heavy lifting until about 1980.

Some amateurs in the US decided to try it over the air and succeeded. One of the keen developers/builders of this pre-war SSB on radio was one Arthur Collins. Collins Radio became a big company and then became Rockwell/Collins.

So the development of SSB was a commercial thing, but it was amateurs that pioneered shifting it off of landlines and onto radio. The view of the professionals at the time was that radio channels weren't stable enough.

David

[G6Tanuki]

Fascinating find: SSB was really 'bleeding edge' tech for anything but the Military [and radio-hams, whose lives didn't depend on it working] in the late-50s/early-60s.

I'll be fascinated to see what is revealed once you get the covers off. It'll be valves, of couirse - though __perhaps__ there will be a couple of power-transistors in an inverter to supply the HT.

[trh01uk]

Originally Posted by Radio Wrangler

So the development of SSB was a commercial thing, but it was amateurs that pioneered shifting it off of landlines and onto radio. The view of the professionals at the time was that radio channels weren't stable enough.

David

I gather from this article that the first commercial radio transmission using SSB as in 1927. And that was for a transatlantic link between Long Island, USA, and New Southgate, England, and was operated at the UK end by the British Post Office. This article says the experimental station before it operated on 57kc/s, and another article says "about 60kc/s".

At such low frequencies the challenges of stability and filtering are much reduced of course compared to SSB at HF (or higher).

It seems the first SSB use by radio amateurs was in USA around 1933/34 with this article appearing as early as 935: QST magazine, October 1935: "Background for Single-Side-Band 'Phone" (it starts page 33).

Apparently there were earlier articles 1933 -34 in R9 magazine, but I can't find online copies of those.

It does seem though that stability problems were the main technical issue in the late 20s and early 30s. Here's one comment from "History of SSB":

"From the beginning equipment stability problems slowed development of SSB. In 1927, a trans-Atlantic SSB commercial radio circuit was in place, but at low frequencies. In fact, it was in the mid-1930’s before commercial shortwave SSB was practical—the frequency stablity problems were solved by using new generation AFC equipped receivers and a pilot carrier from the transmitter."

Richard

[Radio Wrangler]

The bulk of transatlantic traffic eventually went to FDM over multiple coax cables bundled together and sunk in the ocean. Repeater amplifier units were added at intervals and special long life valves were developed. Oddly the DC power for these things had them strung in series with shunt regulators. The undersea cables had huge voltages to add up all the repeaters and ohmic drops applied to their ends. There were some radio links, but at the frequencies they first thought of using there wasn't enough bandwidth for the capacities. Radio links were seen as back-ups, but were nevertheless used to earn what revenue they could. Around the middle nineteen twenties the distributed amplifier and lattice crystal filter were developed as well. There was a lot going on, a good bit earlier than most people would expect.

David

[John KC0G]

Re. post #3, please see http://www.arrl.org/files/file/Techn...df/McElroy.pdf for an article titled "Amateur Radio and the Rise of SSB". The Collins KWM-1 transceiver was introduced in 1957. It was replaced by the KWM-2 in 1959. For information on other products in that period please see http://www.arrl.org/files/file/QST%2...obrien0107.pdf

The December 1956 issue of the Proceedings of the Institute of Radio Engineers was devoted to single sideband. The articles contain many references to earlier work. For more complete coverage of historical papers there is the very good and extremely rare "Single-Sidebands in Communication Systems: a Bibliography" which was compiled by Mildred Benton and published by the U.S. Naval Research Laboratory in 1956. Because it was written by a U.S. government employee in the course of their work, it is no longer under copyright. It can be found at https://books.google.com/books/about...d=BSAVtwAACAAJ

Re. post #6, I have also been unable to find the articles from R/9 in 1933 and 1934. I have seen very few copies of that magazine. It merged with Radio in January 1936.

Re. post #7 and crystal filters, Warren Mason's seminal paper "Electrical Wave Filters Employing Quartz Crystals as Elements" was published in the July 1934 issue of the Bell System Technical Journal.

73 John

[crackle]

Thanks guys for your contributions. This item has turned up in Australia, and the owner had contacted the Radio Museum for more information. They are watching this thread with interest.

Thanks
Mike

[crackle]

A few more photos have been sent in which I can share here.
I am assuming the first 2 are the PSU and the 2nd 2 the transceiver.
Mike

[Radio Wrangler]

Power supply and audio output in the first two pictures, but there are too many valves for just an audio stage. They're no high enough power types for voltage regulation, so there's something more than audio going on. The labelling on the controls ought to give some clues.

In any SSB radio, the key component is the sideband filter, and that horizontally oriented box in the third picture is a likely candidate.

The structure will be a superhet on both transmit and on receive. The yellowish lumps will be crystals. Up top right will be the one setting the carrier frequency on trnsmit as well as the carrier to be reinserted on receive. Bottom right-ish is a bank of four crystals to set the channel frequency. So in-amongst those switched quadruplets of screened coils will be an oscillator and mixer. It's obviously a 4-channel set. Likely the receiver's tuned RF stages will be re-used to remove the image from the TX mixer.

The connections to the PA coil are a bit long and straggly for the top end of the HF band, so I guess it'll be for lower frequencies.

Is that PA valve a TT21 I wonder?

David

[PeterRoberts]

There's a brief circuit description here and an advertisement on page 59 of this magazine.

Peter

[G6Tanuki]

The WW article says both the transceivers described use the Mullard QV06/20 (better known as the 6146).

The photo shows a couple of these - meaning the transceiver should be good for 100W PEP output.