Portadyne Challenger

 This portable radio dates from 1932 and like its contempories is very heavy, even without the accumulator, HT and grid bias batteries it needed.

It has an internal frame aerial and a mechanism on the bottom of the case for turning it to the best signal strength or to minimise unwanted interference. If that failed to provide acceptable results on a picnic one could string out a long wire over nearby trees.


 Because the set might get bumped around, the rear cover is very solid, and a hole is provided through which to poke the leads if there wasn't enough space inside for a large accumulator.

 Above are the tuning knobs which need to be kept roughly in step.


On the right a side view of the cabinet showing one of the carrying handles.





Below you can see how the flap lifts up so you can tune the set and twiddle the wavechange and reaction knobs.

There's considerable wear to the metal panel so the set must have had a tremendous amount of use.


 Above, a rear view showing the four valves. Many portables around the date this was made used 5 or 6 valves but with the advent of tetrodes and pentodes having lots more gain only 3 or 4 valves were needed.

Below, you can see what looks like a much later loudspeaker has been added, together with a transformer. Early sets used a high impedance speaker which was liable to failure due to the extremely thin wire used in the coil. I'm not sure for what purpose are the four large condensers tied in place? The bunch of wires terminated at the bottom of the case are mainly connections to the frame aerial coils.


 The Portadyne uses four valves of which the most interesting are the two pictured here. The RF amplifier is a Mazda SG215, a tetrode with a B4 base and anode top cap. Unlike many old tetrodes I've seen, this example was never metalised. Then there's a Mazda HL2 triode RF amplifier with B4 base and a metalised finish. Next another similar HL2 detector/LF amplifier followed by a Tungsram PP2 output valve, above right, with a B5 base. This last valve is a bit of a puzzle because the Portadyne information I have tells me that the output valve is a triode with a B4 base so it's possible that both the loudspeaker and the output valve were replaced at the same time. Another clue supporting this, is that I've read that the B5-based PP2 was only introduced in 1936, 4 years after this set was made.

Also, I'm not totally convinced the original Challenger had two HL2 valves.


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