It was described as a tropical man pack R.T. Set. (That is an amplitude modulated walkie-talkie in more current terms.)
The set included a dry battery, aerial rods and ground aerial, all carried in a Satchels Signals No 10.
The set covered the frequency range 7.4 - 9.0 Mc/s and was a much improved receiver compared to the Mk 2 version. The range covered was 1 mile with a 4' aerial and 3 miles with an 8' aerial.
On most examples of this set seen today the battery cables have perished badly and it is a rare example that has them in good condition.
As this mark was carried on the wearer's back, the send/receive switch used a mechanical extension cable whilst the Mark II, which was carried in front of the body, had a switch on the set itself.
Total weight of the set was around 21lbs.
Power requirements were 150 v H.T. and 3v L.T.
The battery had a capacity of 20 hours operation.
Send currents are 16ma H.T. and 500ma L.T.
Receive currents are 9ma H.T. and 250ma L.T.
Receive plus Calibrate uses 300ma L.T.
The valves consisted of 5 x ARP12 and 1 x ATP4.
© Ian O'Toole, 2009. Page created: 29/08/04 Last updated: 11/12/2009