Made by The Radio Communication Co Ltd
of London, this brass tuning condenser has the maker's trade
name "POLAR", and the impression 0.0006 on the inside
of the end plates. This component like the other shown has specially
shaped plates so that the high frequency end of the waveband
tuned more slowly than it would have done if the plates had been
symmetrical about the spindle. This is known a a "Log"
type. "Polar" also appeared on vernier coil holders,
for adjusting the mutual inductance between adjacent coils, and
filament fuses aimed at preventing the loss of your battery valves
when the HT battery was inadvertently connected wrongly. These
were advertised by the slogan "7d will save you 17/6d"
in 1923. There were also complete Polar receivers. Polar advertised
the R.C.C. unit, merely a combined anode resistor and coupling
condenser, and took great pains to proclaim its superiority over
the coupling transformer when applied in sets having more than
one stage of amplification. Of course they didn't explain that
you needed more than one stage when you used the RCC unit as
the step- up advantage of the transformer was absent.
Because anything associated
with radio, in the 1920s was horrendously expensive it was common
practice, to not only build your own radio but also your own
tuning condenser. For this you could purchase ebonite end plates
for a shilling a pair, and aluminium or brass vanes, the former
type for as little as 6d per dozen in 1923. Then, the same supplier
advertised a complete 500pF tuning condenser for the princely
sum of 4/6d plus an extortionate 1/3d postage. Things never change!