I happen to have my small Match Box open. It too has had the relay and
all removed. The tap is at the 3rd turn. This appears to be consistent
with the paperwork. The remaining turns of the link were there to give an
approximate 300-ohm output for a separate receiver, designed in the days
when a. separate receivers were used, and b. when the input to them was
typically a terminal strip with a 300-ohm (or thereabouts) input. In case
you have the larger unit, 3 turns on the smaller MB is about 1/2 the coil
I recommend using the full coil only if one is going to add a series
input capacitor--something in the 350-500 pF range might do well with the
full coil. However, since the tap is there, one might use a ceramic
switch and use the 3-turn point for the upper bands (to increase the range
of impedances to be matched by virtue of having a higher secondary to
primary turns ratio). If such an input capacitor is added, please do not
stunt on its plate spacing/voltage rating. References to the use of
receiving capacitors are essentially to the types of capacitors used in
the 1930s and 40s, not to the much smaller and more closely spaced units
used after WWII.
However, the MB should give good service at turn 3 and without modifying
the unit for the series input capacitor.
Hope this is useful.
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