Tuesday, December 10, 2019

The Whaddon Mk VII - Paraset Clandestine Radio What is a Paraset? from http://n6qw.blogspot.com/

No I didn't say parasite but Paraset! 

Bottom Line the Paraset was a clandestine radio set built in England and supplied to agents operating behind enemy lines in the European theater during WWII. Most went to the French Resistance; but some found their way into the Scandinavian countries. 

It is believed that Torstein Raaby, the radio operator on the Kon Tiki voyage used the Paraset while a Resistance Fighter in Norway during WWII.


The whole radio was stuffed inside an innocuous looking scruffy suitcase. The standard issued radio even included some spare tubes right in the case.







What is up here?




At first I thought it would be nuts to rely on such a radio as your primary communications link with your headquarters. Then I forgot that the British had 10,000 National HRO Receivers parked about 100 miles away whose only job was to copy your signal and at the same time some very powerful radio stations sending RF in the other direction. So perhaps when the whole system is evaluated not all bad.

It was quite an interesting radio receiver / transmitter that I previously mentioned was stuffed into a small suitcase so that it would be disguised. 

There were several options for powering this rig including from the mains as well as from a DC power pack (vibrator supply). 

The basic scheme was a two tube (6SK7's) regenerative receiver and a one tube (6V6) CW transmitter crystal controlled operating in the 3 to 8 MHz range. The receiver tuned the same range. The power output of the transmitter was at best about 5 watts. Keep in mind friend Bill, N2CQR has made 20 contacts on 40 Meters running a one transistor regen and one transistor transmitter at 100 Milli-watts. Some DX is like 1000 miles away --so 100 miles with 5 watts is a cake walk!

The transmitter tuning used a two light bulb system (Load & Tune) for indicating maximum RF Juice to the antenna. For antennas don't think of 40 Meter dipoles strung between two trees at 100 feet. Often a chunk of wire was thrown on the floor or perhaps strung around a room.

Many hams world wide have taken up the challenge to replicate this amazing radio and the internet abounds with many replica examples of the Paraset.

I tried my hand at building just the transmitter section and found it to be somewhat underwhelming. I also did some preliminary work on the Dial Drive Mechanism which was friction drive controlling the main receiver tuning capacitor














73's
Pete N6QW

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