After testing the
RF24 I tried this RF26.
The results were not quite right.
I can see the oscillator but the tuning passband is absent indicating
a probable fault with the unit.
I checked three dial settings,
zero, a mid range and 100 corresponding to the oscillator frequencies
seen below, 50.175MHz, 53.55MHz and 66.525MHz. The EC52 oscillator
was OK but no sign of the receivers pass-band
(approx 8MHz below the oscillator) as can be seen in the RF24
and RF25. This may be connected with the cut wire at the
centre valve (which I soldered back in place). Maybe indicative
of an old fault-finding exercise by a previous owner? Maybe cracked
glass around a pin of one of the two EF50s?