General coverage communications receiver
The AR-88 was a valve-based shortwave
general coverage communications receiver,
developed and built by the Radio Corporation of America (RCA) in the
early 1940s. Although the receiver was initially intended as the successor
to the AR-77 amateur receiver, the outbreak of WWII made it evolve into
a professional high-end military-grade receiver for which cost was no
The AR-88 is a 14-valve (tube) receiver, which covers a frequency
range of 535 kHz to 32 MHz.
Unlike the National HRO receiver,
which had pluggable coil packs for
each frequency band, the AR-88 uses a six-position
A special version of the receiver, the AR-88LF, was suitable for LF
and MF, covering 70 to 550 kHz (continuously) and 1.5 to 30 MHz (continuously).
The image on the right shows a typical AR-88.
It measures 49 x 28 x 49 cm and weights over 40 kg.
Judging from its low serial number (100227) it was produced in the early
years of the war .
As most of the first production runs of the AR-88 was supplied to
Great Britain, Russia, France and China as part of the 1941
lend-lease act , it is likely that this one was used in the UK,
for example for intercept work. It is finished in black wrinkle paint,
which was typical for the early models.
It was often supplied as an 'open frame' for 19" rack-mount purposes,
but could also come as a cased version, in which case the 19" radio
was built inside a black wrinkle paint cabinet with a lid in the top panel.
Later versions came in a variety of colours and finishings (e.g. grey).
It is estimated that a total of approx. 25,000 AR-88s
(all variants) were
built during the war .
After the war, the AR-88 became a popular receiver for radio amateurs,
who used them well into the 1960s. Some receivers are still being used
by amateurs and radio enthusiasts today. A typical feature on some of the
surviving AR-88 radios, is that most of them have an alternative
behind the rightmost window on the front panel.
The reason for this is that
during WWII, most receivers were shipped without the original S-meter, due
to world-wide shortages of such meters. The receivers that were used for
diversity reception didn't need an S-meter, and the AR-88s using for
interception in the UK were often equipped with an alternative meter
by the British.
- 0.54 - 1.6 MHz
- 1.6 - 4.5 MHz
- 4.5 - 12 MHz
- 12 - 16.5 MHz
- 16.5 - 22.5 MHz
- 22.6 - 32 MHz
During WWII, the British intelligence service, GC&CS (now: GCHQ),
ran a massive operation of intercepting and decoding German radio
messages in morse code,
mainly encrypted using the well-known
Enigma cipher machine. The messages
were intercepted by the so-called Y-Stations.
These Y-Stations were spread all over
the country, but were also present in other parts of the world, such
as North Africa and Australia. Those Y-Stations were operated by
Ham Radio operators and specially trained house-wifes, the so-called
Y-Service, using a variety
of intercept receivers, such as the AR-88
and the HRO.
Once the messages were intercepted, they were sent to the codebreaking
center at Bletchley Park by despatch rider or via
teleprinter lines (telex). There, a team of over 12,000 people,
broke the German codes at a large scale on a daily basis.
As many receivers were required for the war effort, the UK ordered
large quantities of AR-88 receivers from 1941 onwards.
These were provided by the US under the so-called lend-lease act
of October 1941 .
The receivers were supplied as stand-alone as well as rackmount units.
The image on the right shows an intercept room at
Beaumanor Hall, one of the most prominent Y-Stations in the UK.
In the room, an long array of intercept desks was present,
each with its own operator. The image on the right shows a single
desk with the necessary paperwork and a pair of headphones.
At the right is a 19" rack with two RCA AR-88 receivers.
The device at the front left is a so-called undulator,
a recording device that could write morse code as a series
of square waves onto a strip of pre-gummed paper.
The intercept rooms were located in the main building
(Beaumanor Hall) as well as in a series of wooden huts, disguised
as stables and cricket pavilions. Other receivers were used here
as well. The signal from the various antennas were distributed
to all receivers on the estate .
The lend-lease agreement commanded that the receivers had to be returned
or destroyed when they were no longer needed. Many AR-88s were
therefore destroyed after WWII had ended.
This is probably the
reason why so few AR-88s are found today. The ones that did survive
were often bought back by the UK (for a fraction of the actual price)
after they had formally been returned.
The manufacturer, RCA, didn't want to see any of them back on the US market
The AR-88 also played an important part for intercepting German
Wireless Traffic (WT) that was created with the
Lorenz SZ-40/42 cipher machine.
The SX-40/42 was known as TUNNY by the allies, and was in fact a heavy
mechanical coding machine with 12 cipher wheels, that was used for
the encryption of teletype traffic (telex).
The telex signals were first encrypted using the SZ-40,
and then sent via short wave radio, using Frequency Shift Keying (FSK).
At the other end the traffic was decrypted using another SZ-40.
In the UK, the German signals were intercepted by the various Y-Stations,
and sent to Bletchley Park (BP) for decoding.
At BP, a team of methematicians led by Bill Tutte, managed to create
a working electronic equivalent of the TUNNY machine, without ever having
seen a real Lorenz SZ-40. Unlike the mechanical SZ-40, the TUNNY machine
used electronic valves (tubes).
The image above shows Sarah Marlin and Debby Minney in ATS uniform,
re-enacting the intercept of TUNNY traffic at the Tunny Gallery opening
day at The National Museum of Computing in May 2011 .
In Great Britain, the AR-88 was not only used for interception of
enemy radio signals, but also for communication with ships and
airplanes. The photograph on the right was taken in the secret
Underground Headquarters (UGHQ) under Fort Southwick,
hidden deep down in the Portsdown Tunnels .
On D-Day, this was the Allied communications center for
An AR-88 is visible on the left,
being operated by a WRENS (Womens Royal Navy Service).
The clothing of the other operators suggest that this was
the Naval wireless transmission room (W/T).
Portsdown is located to the north of Portsmouth (UK). It consists of
approx. 5 miles of tunnel constructions, hidden in a 120 metres high
chalk hill that is locally known as The Hill.
Most of it was created during WWII.
More information about the underground headquarters (UGHQ),
the Portsdown Tunnels and Fort Southwick,
is available from Bob Hunt's excellent website .
- Henry Rogers, RCA's Amazing AR-88 Receivers
Website: Radio Boulevard. Western Historic Radio Museum.
1997-2012. Retrieved December 2012.
- Wikipedia, RCA (Radio Corporation of America)
Retrieved December 2012.
- Wikipedia, WWII Lend-Lease Act
Retrieved December 2012.
- Museum Jan Corver, AR-88 Receiver - THANKS !
RCA AR-88 receiver featured on this page kindly donated by Museum Jan Cover.
Budel, The Netherlands.
- Bob Hunt, Portsdown Tunnels
Website, Retrieved December 2012.
- Personal correspondence with Kevin Coleman
Volunteer at Bletchley Park (Station X) and Beaumanor (Y-Station).
December 2008 - January 2009.
- The National Archives, Image of radio intercept room at Beaumanor Hall
National Archives (UK) reference: HW41-119.
- John Robertson, Photograph of Y-Station re-enactment
The National Museum of Computing (TNMOC), TUNNY Gallery opening day,
26 May 2011.
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© Crypto Museum. Created: Saturday 05 December 2015. Last changed: Saturday, 06 October 2018 - 15:52 CET.