[Drake] R4C Filter loss/mode independent of bandwidth selection

[Harvey Hetland]

Scott:

The later versions of the Drake R-4C using 6EJ7 tubes has a transformer
T7C with a center tap that is switched with S2A rear.  This adjustment
can be quickly done while in the narrowest filter and in either the 0.5
or 0.25 kHz bandwidth by adjusting T7C for maximum while listening to
the crystal calibrator.  This adjustment is very critical to minimizing
the loss through the filters in the 0.5 and 0.25 kHz positions.  The
location of T7C is on page 5-6.  Instructions are on page 5-2 under the
paragraph 5-7.  This adjustment will probably vary between different
Drake 500, 250 or Sherwood 125 Hz filters used in these positions and my
experience has been that it should be done for the most narrow filter
and redone if that filter is changed.

Earlier versions with 6SH6 tubes did not have this center tap in T7, but
the notes on page 5-2 still apply for optimum performance.  Good luck.

Harvey, N6MM.