Wireless Sender No. 12

HF transmitter Wireless (Set) Sender No. 12

Wireless Sender No. 12 was developed in 1940 as a medium range general purpose transmitter for static and mobile use. Its companion receiver was Reception Set R107, fitted in a similar transit case. The No. 12 Set is self contained and fitted with an internal mains power supply. When after the war the No. 12 Sets were released to the surplus market, they were very popular with radio amateurs as virtually nothing else was required to get it working on the 160 to 20 metre amateur bands. Although relatively little were produced, these sets are still around, many in original unmodified condition.

• Frequency range 1.2 - 17.5MHz in four ranges.
• RF output approximately 7W AM and 25 W CW.
• Power supply 100-250 V AC mains. About 260 watts consumption at full power.
• Transmitter has three stages: ATS25 (807) Master Oscillator (VFO or crystal controlled), ATS25 (807) Buffer/Amplifier and ATP35 RF Power Amplifier.
• For more technical details of Wireless Sender No. 12 see the Wireless sets page.
• Modulation is done in the suppressor grid of the RF Power Amplifier

Note that the quality of the pictures taken from this set are not optimal. This is not caused by being impressed by this historical set, but merely the heavy weight of this beast which prevented me to take it to a more suitable spot at where the lighting was better.

Detailed internal views of Wireless Sender No. 12

Top chassis view of Wireless Sender No. 12. The set is build very conservatively, and each component is compared to later war-time standards much over dimensioned. The mains transformer in the centre of the chassis alone has a weight about 40lbs, the chassis is made of 2mm steel sheet. Still, this set has nice construction details as will be seen on the other pictures in this page.

	Left hand side view of chassis showing coil turret of Master Oscillator.		Variable inductor (tank coil) of RF Power amplifier and aerial coupling coil. Note RF Power Amplifier valve and two HT voltage stabiliser valves.
	Left hand front panel view with MO access door opened. Note Buffer coil turret below meter.		Right hand front panel view with RF PA access door opened.
	More detailed picture of MO and Buffer compartment. Note MO valve (partly hidden by crystal) and Buffer valve.		Detailed view of RF Power Amplifier showing ATP 35 valve. Note RF pick up socket for connecting a wavemeter just above the access door.
	Component layout of Master Oscillator/Crystal Oscillator stage.		Under chassis components layout of Buffer stage (centre) and RF Power Amplifier (right).