Home:  Military Comms: RACAL RA17L RECEIVER, 1954


View all Military Comms


The RA17 series of communication receivers,were high Quality, valve sets,first produced by Racal,in the the 1950s,they were originally designed for supply to the British Navy.The design proved successful, and they were ultimately used by all the services and were to become the main receiver of the British radio surveillance organisation,known as G.C.H.Q.
This is the unit that put Racal 'on the map', utilising the famous Wadley Loop circuit. The Racal Factory was closed in 2000 bought by an American Company, the factory was in 2006 a derelict site

Your comments:

  • For history when I worked at Racal Slough the the head draftsman was a man called Frank Hall in conversation one day it came up that he was the actual man with the hacksaw that famously made the chassis cut back in the days of the start-up company in Bracknell he also mentioned how much sweat he had perspired on completion.

    .......... clive brett, Elsecar Yorkshire, 17th of April 2022

  • I have actually seen the original RA17 with its famous saw cut.

    The problem of the many spurious signals was almost certainly due to eddy currents flowing within the vertical metal screening of the two adjacent VFOs. The saw cut physically isolated the VFOs. The manual warns to ensure that the two modules are fitted with a vertical gap and that all modules are clean and tightly bonded to the chassis.

    It was displayed at the HQ in Bracknell but later disposed off and eventually a good friend of mine acquired it. He later donated it to a technical museum.

    The original panel colour was mid-grey, the meter and loudspeaker escutcheon were square and the knobs were the standard fluted ones often used by Marconi. Production models were changed to the colour scheme and Berco knobs that we know today.

    The mechanics of the film scale are probably the best ever built.

    The RA17s come in many different models, from the the original RA17 to the RA17W. The 17L is the most common. I have four RA17Ls and the very rare RA71 destined for the ham market, but it was probably too expensive for most hams.

    Numerous add-on adaptors were made for RA17s. The RA237 extends the tuning range down to 10kHz and was much used for submarine comms. The RA63, RA98 and RA218 are for SSB/ISB. The RA66 is a panoramic adaptor often used for electronic warfare. The MA197 is a massive front-end pre selector to protect the receiver from nearby transmitters, typically on board a warship. The MA1350A locks the VFO to a minute fraction of a Hertz.

    These radios were sold all over the world and put Racal on the map.

    This equipment is now about 60 years old and will need a lot of TLC and skill to restore them to the original spec, but it can be done and there are keen internet groups with the relevant experience.

    These wonderful radios were a lot better than the subsequent early transistorised RA217/1217 series until the fully synthesised RA1772 series arrived in about 1974.

    No one will ever make such radios again.
    .......... Michael O'Beirne (G8MOB), Surbiton, Surrey, England, 5th of February 2021

  • I believe this wonderful piece of kit actually arrived in 1964 not 1954. I
    was trained on it in 1965 in my role as an army radio technician.
    The set had 23 valves in it and I knew the function of every one and loved
    working on it.
    We also used Edison receivers which weren't a patch on the design,
    reliability, stability and capability of the RACAL, and were always in the
    workshop for realignment or other issues.
    The RA17 was a masterpiece of mechanical and electronic design and
    engineering and was really ahead of its time.
    The separate tuning controls for MHz and KHz was unique at that time, I
    believe. A truly beautiful piece of kit!!!
    ........... Geoff G, 11th of April 2015

    .......... Geoff Grandy, , 20th of March 2018

  • Worked at the BBC monitoring station at Crowsley Park (linked to Caversham Park). We used large numbers of RA17s in both the interception room and in the relay room (as well as doing monitoring work we also received and relayed VOA and CBC programmes). Quite tricky to align particularly the loop filters. The construction was a series of die cast boxes and when a unit would not meet spec gentle use of a small hide faced mallet on lids to improve earth contacts often helped. We also used a few RA1772s at the supervisory desk in order be able to quickly select an alternative frequency when a frequency to be monitored failed to perform
    .......... Robert Lee, Exmouth UK, 15th of September 2015

  • I first got to play with an RA17 as an apprentice in the GPO at Somerton Receiving station, C 1959. Having built a number of radios as a teenager, I found the RA17 an enormous leap forward. Later, in the 70s, I bought one at a radio rally. It made my B28 look obsolete! I was told a story that Racal had a stability problem when they moved from prototypes to the first production radios. These were major contracts with the Goverment and to fail to deliver would have likely sunk the Company! Almost nothing they did cured the spurious oscillation. Finally someone took a hacksaw to one of the RA17s and cut a slot in the chasis. This cured the problem and demonstrated the underlying cause. The success of the RA17 and the Company is now history. Apparently the actual radio along with the hacksaw was put on display in the Company headquarters as the "modification" which saved Racal. Does anyone know if this particular radio and hacksaw ever made it to a museum when Racal closed?
    .......... Dr Brian Ray G8MUE, 5B4AHW, Paphos, Cyprus, 2nd of June 2015

  • Definitely a special piece of kit though I preferred the URR391....the wadley loop systems and all mutual compensation systems were breakthroughs. What made my heart glad reading these comments was the affection some showed for Morse...getting rid of it officially was like killing a mocking bird..
    .......... Tony Clancy, Sydney Australia, 18th of November 2013

  • One of the finest receivers ever produced. The BBC had banks of these in their monitoring station, sold them off and replaced them with digital versions, within a year they were out trying to buy back the old ones, nuff said.
    Worked on these and was also lucky enough to own one.
    .......... Mark Corder, Sidcup, 25th of December 2012

  • An excellent piece of kit that when I saw it after near forty years it sent my Morse key fingers twitching. The schedule to operate the set; every squadron leader deserves a crafty fag was unforgettable. Zero beating to a frequency was always a cert and the fine tuning was its hallmark especially when trying to find a signal from a victor tanker in the early hours of a back shift in the Commcen.
    .......... Ralph Hodgson, Barnstaple UK, 27th of June 2012

  • As far as I know, Racal was not bought by an American company but by th French conglomerate Thomson CSF. There after it evolved into simply Thales.
    .......... I Ropper, West Lothian, UK, 18th of February 2012

  • I was a Spec Op in 1960s, and before I left the Signals I started worked with a 19 inch rack mount of 19 of these RA17s. 18 of them were pre-tuned to station frequencies and selected in sequence by uni selector and fed to one earphone to listen out for activity. The last RA17 was for manual search into the other ear piece.

    I now use a (most mode) scanner(similar) AOR 2800 but 100Khz to above 1000Mhz that fits in the pocket.
    .......... Patrick Wraith, Bristol, 1st of September 2011

  • I think its worth explaining why the "Wadley Loop" was such a breakthrough and why it put Racal "on the map".

    Receivers generally (not all of them) prior to the RA-17 suffered from "frequency drift". What that means is that while you are listening to a signal, reception gradually deteriorates because the receiver is wandering off the frequency of this signal, and then you have to re-tune, etc, etc.

    Why did they do this? Well, there a number of reasons, the principal one being that changes in temperature make the parts determining the tuning of the receiver change very slightly, thus moving the receiver to a slightly different frequency - i.e. to "drift".

    And in a valve set (and the RA-17 is all valve) there is a lot of heat generated by the valve heaters. So, the set gradually heats up after switch on, and the set can easily drift markedly for an hour or more as its internal temperature stabilises.

    The Wadley Loop cleverly cancels this drift completely. The relevant circuit parts still drift like mad, but it has no effect whatever on the frequency the set is tuned to. Very clever indeed!
    .......... Richard Hankins, Ross-on-Wye, 8th of June 2011

  • Having worked on the RA 17L for over 20 years, it was equally adaptable in receiving Morse or r/t signals. A frequency range of
    500kcs to 30mgs was a vast improvement over the receivers in use at
    its commissioning into the Armed Forces Communications. It brings
    back many happy memories from 1964 when working air to ground,
    Morse with both Victors and Valiant 'V' Bombers.
    .......... Mick Skidmore, Nuneaton, Warwickshire, 17th of October 2010

Add a memory or information about this object


©2007 The Museum of Technology, The Great War and WWII
Company registered in England No. 7452160, Registered Charity No. 1140352, Accredited Museum No. 2221