[Racal] 18 kHz band pass filters

[Brian Goldsmith]

Greetings to all.
In the Racal RA121 Independent Sideband Adaptor (and the RA98 which has
essentially the same front end) the 100kHz IF output from the RA17/RA117
receiver is mixed with a LO of 118 kHz to give an 18 kHz output.This output
is passed through a T section filter which is tuned by three adjustable
potcores which have series/parallel capacitors depending on which part of
the T they are in.The handbook says,"This filter is a single section
constant K having a sensibly flat response from 12-24 kHz".Would anyone care
to comment on what "sensibly flat" means given the response of a "single
section" filter would be fairly peaky at 18 kHz.

Brian Goldsmith.