The top view with labels. The box measures 120 x 95 x 57 mm.
With low cost ic's available it became possible to change from a single tone to modulate the transmission to a pip tone. This pip tone made finding and identifying a signal much easier. If the band had more than one signal, or if ones own equipment produced spurious noises, knowing that a pip tone was being sought was a comfort. It was not unusual for the pip tone to be relayed over the 2M talk-back. Initially as an aid to identification and subsequently the received signal was fed back to the transmitting station so they could optimise their dish in azimuth and elevation. The latter was often vital as the FM signal has a characteristic of going from a perceived 5/9 to a 3/1 with a small change of signal level.
The internal layout.
The label says that it is a stabilised supply. Inside the circuit consists of a 7805 ic voltage regulator arranged to give a variable voltage output. This is fitted with a heatsink. The microphone amplifier is formed around a single transistor. The CMOS 4001 quad NOR gate ic is used as a pair of square wave oscillators, one tone and a low frequency pip generator to gate the tone circuit.
Front view with four position function switch.
Quarter inch mic jack socket.
Clearly a re-cycled project box.
This exhibit was last updated on August 20, 2014.