Sometimes, while searching for vintage radios, you get a real surprise. One such instance happened to me a couple of years ago when I visited John Sheard in Mount Gambier, to see his collection of vintage sets.
When I got there, I was immediately ushered down the hall to the room where his collection was housed. And did I get a shock because there in the corner was what appeared to be one of the original six pedal radios built by Alf Traeger in 1929, for use in the Aerial Medical Service (the predecessor to the Royal Flying Doctor Service).
In researching my book, “Outback Radio from Flynn to Satellites”, I had previously concluded that none of these original sets had survived and yet here was one fully restored. I just couldn’t believe it. Then John let me into the secret; this set is a replica of the original and matches it closely in nearly every detail.
This is the view inside John Sheard’s replica pedal radio. The degree of authenticity is astonishing.
In fact, he had used the information in my book, including the photos and the circuit, to build this great working replica.
Back in 1928, Alf Traeger, with help from his mentor Harry Kauper, built what proved to be the first transceiver capable of being used by non-technical people in remote areas without mains power. This meant that the transceiver had to be frugal in terms of power usage and in order to generate enough energy to operate the transmitter, a high-voltage generator was used. The final testing of the first practical pedal radio took place in November 1928.
The pedal radio transmitter used a single B205 triode as a crystal oscillator-cum-output stage. The transmitter had an output power of 1-1.5W on Morse code at a frequency of 2230kHz. It was a Morse code-only transmitter as Traeger, Kauper and many others had told the Reverend John Flynn that voice transmissions were not practical at that time due to the high power consumption of such transmitters.
Indeed, “low-power” battery valves suitable for use in voice transmitters did not become available until the mid 1930s.
The receiver in the pedal radio was a 2-valve regenerative TRF (tuned
radio frequency) unit. It employed two A141 space-charge tetrode valves that required no more than 20V on their plates, although in this set only 9V was used. There was just one tuned circuit but two separate coils were used to gain the necessary coverage. One coil allowed the set to tune the broadcast band while the second coil is believed to have tuned from around 1.5-4MHz.