(c) 1999,2008 Peter McCollum
The SSTR-6 and SSTC-502 - "Joan-Eleanor"
This system, nicknamed "Joan-Eleanor", was developed
beginning in late 1942 by Dewitt R. Goddard and Lt. Cmdr. Stephen H. Simpson.
Mr. Goddard's wife's name was Eleanor, and Joan was reportedly an acquaintance
of Cmdr. Simpson. The project, originally proposed by Lt. Col. Henry Shore,
involved producing a pair of transceivers; one for use by an agent on the
ground, and the other mounted in an aircraft flying overhead. The system would
be in the UHF band, since it was known that the Germans could not effectively
monitor those frequencies. The agent would make his report using plain speech,
and the aircraft would record the transmission on a wire recorder. Since Morse
was not needed, the agent's training time was greatly reduced, which was
considered a valuable feature in the German theater. In addition, the aircraft
could ask for immediate clarification on certain points, without the delay of
encryption and decryption.
The hand-held SSTC-502 transceiver uses a dual triode as a
combination super-regenerative detector during receive, and an oscillator
during transmit. Two other tubes act as a microphone amplifier and modulator.
The antenna is a simple dipole, attached to the top of the unit. The operating
frequency is 260 MC (the original design was for 250 MC, but it was learned
that the Germans had a sweep receiver that operated up to 250 MC). The only
controls are for regeneration and tuning (apparently for fine tuning only).
Battery power consists of two "D" cells in parallel for the
filaments, and two 67.5V batteries for the plates. Modulation was really a
combination of AM and FM, and was received as an FM signal by the SSTR-6.
The airborne SSTR-6 transceiver uses an 832A tube as a MOPA,
modulated by a pair of 42 tubes. The receiver portion is a superheterodyne with
two RF amp stages, two limiter stages, and an FM detector. Power was supplied
by four 6V wet-cell batteries which operated the filaments and a dynamotor. The
SSTR-6 equipment was mounted in the space normally occupied by an aerial
camera. The types of aircraft used included the B-17 and the British Mark XVI
"Mosquito" bomber. The Mosquito was used for most missions, and was
preferred because of it’s high speed and high altitude capabilities, making it
unreachable to most German defenses.
The handheld “Joan”
(SSTC-502) portion of the Joan-Eleanor system. The upper-right image shows the
folding antenna and earphones connected. Images courtesy of T.B.
The initial design work for Joan-Eleanor was done at RCA
laboratories in Riverhead, NY. The first several SSTC-502 units were reportedly
built by Mr. Goddard personally. The non-prototype units for the system were
built by Citizens Radio of Cleveland, Freed Radio Corp. of NYC, Dictagraph
Corp. of NYC, and Signal-U Mfg. Co. This latter company had a contract for 500
units. Much of the testing for the system was performed at Bovington, England,
beginning in July of 1944. Operational missions began later that same year.
During testing, antenna problems and frequency drift were among the problems
noted.
An antenna accessory was tested, code-named "Mud
Flat". It was a reflector panel, 0.6 X 0.12 wavelength in size, mounted
0.25 wavelength behind the SSTC-502 antenna. The Mud Flat proved to greatly
improve signal quality, and it's use was recommended whenever it was practical.
A corner reflector was also tested, but it was decided that it was too
directional.
Three SSTC-502 ("Joan") transceivers,
shown with the canvas case. The black unit is believed to be a prototype. Above
are antennas (folded) and earphones. Photo courtesy of T. B.
The SSTR-6 (‘Eleanor’) installed in a Mosquito aircraft.
Some items visible in the picture: the SSTR-6 at lower-right, dynamotor P.S. at
lower left, wire recorder at upper center, and the antenna rotating spindle in
the center. National Archives photo.
Click
Here for an image from a
patent filed in 1945 for the push-to-talk arrangement used in the SSTC-502
“Joan” transceiver.
Click
Here for an image from a
patent filed in 1948 for the antenna used in the SSTC-502 “Joan” transceiver.
