Wednesday, December 28, 2016

Paraset Replica Project - Bayou Jumper

First a little bit of history:

Parasets are so named because they were spy radios built by the British in World War and were typically deployed behind enemy lines via parachute - hence the name "Para-set".  Power output was 4-5 watts.

From Wikipedia:  The Paraset was one of the first successful miniaturized radio sets for Britain's Special Operations Executive which conducted espionage and other activities behind German lines during World War II.
The set, known as the Whaddon Mark VII, was used for clandestine radio communication primarily in Norway and Europe, developed at the Royal Signals Special Communications Unit workshops at Little Horwood and the workshops of Whaddon Hall, Buckinghamshire in the early stages of World War II. The equipment is known as the “Paraset” because it was dropped by parachute for field agents.[1][2][3]
A number of amateur radio operators build and operate replicas of the Paraset.[4]

The original parasets were regenerative receivers with crystal controlled transmitters.  The two tubes on the upper left are the receiving tubes and the larger tube on the right is the transmitting tube.  In the middle is a socket that is meant to take FT243 crystal holders for the single frequency that will be used for transmit.  The regenerative receiver has very few parts and is built on the principle of regeneration by providing positive feedback with its output connected to its input through a feedback loop..

The project I am building is a modernized version of the Paraset which uses MOSFET transmitter section based on the NS40 transmitter designed by NM0S of the 4 States QRP group.  The receiver is still a regenerative receiver.  The transceiver is a single band single frequency transmitter.  The transmit frequency can be changed by plugging in a different crystal.    Here is a short demonstration video from the 4 States QRP Group.

The modernized version is shown above.  Gone are the vacuum tubes.  The main PCB is shown below:

I am still awaiting the arrival of the kit.  As you can see, the board is a tight fit into the Hobby Lobby Chinese made boxes the PCB was sized for - so I made my own box.  The box is US made in SC by me. In addition to accommodating the PCB, the box I built have compartments for a battery and antenna wire. I have crystals for 7030 (NAQCC), 7055 (SKCC), 7122 (QRP-ARCI and Bayou Jumper calling frequency).  Larry Hastings, the kitter tells me my kit will go out in tomorrow mornings mail.

I tested the antenna wires today.  It was set up as a resonant antenna for 40m as a quarter wave ground plane.  I had a QSO with WA1HFF in Massachusetts transmitting 3 watts on my K1.

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