1. General description.

(a) Purpose and General Features.

The No.19 set is designed primarily to provide a complete communication system for armoured fighting vehicles. The apparatus also forms the signal equipment in A.C.V.’s and L.C.V.’s (mobile headquarters), when increased range is obtained by using a specially designed R.F. amplifier in conjunction with the "A" set. It is also used as a ground station, in which case remote control facilities are available, working over a ½ mile of line using Remote Control Unit "E".

The following facilities are provided:-

(i) The "A" set

This is used for communication on R.T., M.C.W., and C.W. On R.T. and M.C.W. a range of about 10 miles may be expected, the use of C.W. will increase the range to about 20 miles. The frequency range is 2 to 8 Mc/s, covered in two overlapping bands.

(ii) The "B" set

This is a U.H.F. transceiver providing R.T. between vehicles up to a distance of half a mile. The frequency used is approximately 235 Mc/s.

(iii) The I.C. Amplifier

For communication between members of the crew in armoured formations and between members of the staff in mobile H.Q.

Power for the complete apparatus is derived from a 12 Volt accumulator which drives two rotary transformers, one of which runs on send only. They are contained in a Supply Unit No.1 Mk.III. Battery consumption is 10.7 Amps on "Send" and 7.1 Amps on "Receive". If the Amplifier R.F.No.2 is used there will be an additional current consumption of 24 Amps on "Send".

The microphone and Receiver Headgear No.1 or No.2 used with the equipment is connected to the sets via separate control units located at convenient points of the vehicle, and the facilities required are selected by means of a three position switch on the front of each unit, marked "A", "B", and "I.C.".

Switching from "Receive" to "Send" is accomplished on R.T. by means of the microphone pressel switch, and on W.T. by inserting the key plug.

(b) Aerials

The "A" Set uses a rod aerial for ground wave communication. A.F.V.’s carry a 12 foot rod consisting of three four-foot sections mounted on a flexible rubber base on the outside of the vehicle turret. Mobile H.Q. vehicles use a "V" aerial with the H.P. set consisting of two rods mounted in a "V" adapter. Stationary vehicles may be operated with vertical aerials up to 34 feet in height, or, for skywave communication, with an end fed horizontal aerial, of which six different lengths are issued. A more convenient form however, is the "Aerials Horizontal All Wave A", consisting of a one hundred foot length of stranded copper wire, and joined to the variometer through a coupling unit which can be constructed from ordinary spares, see Fig.24. The 50pF condenser is not normally in circuit but is switched in should the variometer tuning point come on the red band. The switch must be well insulated.

 

 

The "B" set aerial is a half wave rod twenty inches in length, and is connected direct to the set by means of a screened feeder, a multiple of one half of a wavelength.

 

Valves from the 19 set

This picture is not from the original notes.

The valve at left is an E1148, which is the first valve in the 'B' set. The base connections were for heater and cathode only, the grid and the anode coming out to the top caps. At centre is a 6K7G, which is an R.F. pentode. This valve was very common as an R.F. and I.F. amplifier. The audio output valve in the i/c amplifier was a 6V6, a medium-power tetrode. This also found wide use as an audio amplifier in all sorts of military radios. It was very robust - and ran very hot, as much as 250oC. The PA valve was an 807 - see the page on this valve.

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Rod Beavon     17 Dean's Yard      London  SW1P 3PB

e-mail:  rod.beavon@clara.net