The "Paraset" Suitcase Spy Transceiver of WWII. This was one of the first truly successful miniaturized transceivers, built by or for Britain's S.O.E. (Special Operations Executive) which conducted sabotage, spying, and other nefarious activities behind German lines during WWII. The schematic I have shown below is most probably an early version, since another schematic I have shows a different keying system, a bit different transmitter section, and the voltage dividers for the receiver are different.
The "Paraset" receiver covers 3.0 to 7.6 mHz. in one band, while the transmitter covers slightly more than the receiver in two bands, selectable by a toggle switch. Power output is 4 to 5 watts. I think the transmitter is really neat. The transmitter output coupling system has the capability of matching quite large variations in impedance. It seems as though there was much more thought expended on the transmitter than the receiver. It is rather crude even by 1939 standards. There is no "bandspread" tuning in this early version, nor an RF amplifier stage to isolate the detector from the antenna, nor is there any possible provision for any sort of sidetone so that it is impossible to hear your own sending.
Several people have built replicas of the "Paraset" and are operating them on the air.
Mario, IK0MOZ has an entire and very complete web page devoted to this neat little rig . Here is the URL : http://www.qsl.net/ik0moz/paraset_eng.htm.
Also, please see this URL: http://www.qsl.net/ik0moz/LA5MT_Paraset.htm for another working replica.
Here is a nice photo of a "Paraset" which was used by the Norwegian agent Oluf Reed-Olsen, who worked for Britain's SOE during WWII. This is an earlier model which was mounted in a leather suitcase, and may have been known as the SS-TR-1 from the document inside the lid in the photo, but I had thought that the SS-TR-1 was a completely different rig.
This particular Paraset also has a 6 VDC power supply included with it which connected to a car battery via large alligator type clips. The switch is the 80/40 meter bandswitch. There is also a nice all-brass key connected to the rig out of the photo to the left . The plain black knob just below and a little to the right of the band-switch is the emergency key. The pointer-type knob near the center is the transmit-receive switch.
Here is the schematic of an early model as I have it. I no longer know where this schematic came from since I first found it at least 10 years ago, although I do remember that the source was some European website and the person who did this "reverse-engineered" an original Paraset. Apparently, from discussion on this rig, it is very difficult to "reverse-engineer" it since it is so tightly packed that in order to do a proper job, the rig must be at least partially disassembled, and no one wants to do that to an original Paraset! In a recent discussion with Henk in the Netherlands, between us we determined that there are at least 5 DIFFERENT versions of the Paraset schematic floating around out in cyberspace. After examining all those I have access to, including this one, I am reasonably certain this schematic correctly represents an early model Paraset.
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