Cabinet made of mahogany, with
Bakelite face plate; the controls and fittings
are nickel plated. The radio was designed for
use with headphones. On the left of the
faceplate there are two small holes where the
headset can be plugged in. On the right four
antenna terminals, numbered 1 to 4, with a solid
link that can be used to connect terminals 3 and
4. Connecting an antenna to these terminals in a
number of different ways, the frequency range of
the radio can be changed. This also affects
sensitivity and selectivity, which seems a lot
more complex than a wireless broadband router or
a DAB radio, but is actually relatively
straight-forward. The battery control
knob (top left) is used to increase the voltage
supplied to both tubes; the amplification knob
(bottom left) decreases or increases the amount
of regeneration. The station selector lever
(lower right) selects the desired frequency.
The thick cloth cable coiled to
the left contains the battery wires. The wires
are individually labelled with small metal
plates.
The tubes used (type 11) are
quite scarce and filament breaks easily. In 1925 RCA
issued a number of service sheets showing how to
convert the Radiola III to the more reliable 199 type
tubes.
This is a Swedish version of the
Radiola III. The name "Radiola III" was removed
in two places: on the face plate, below the RCA
logo and on the back the name "Radiola III" was
painted over. In Sweden these radios could not
be marketed, because SRA - Svenska Radioaktiebolaget -
in Stockholm, already used this name for its
products.
The
real values for the capacitors below the
four antenna connections were found by
experimenting with an artificial antenna and
measuring the frequency range; most circuits
show the wrong values! (See
circuit)
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