"Is there any compensation for the insertion loss of the filter?"
Yes, the filter board includes a transistor amplifier; however the roofing
filter is only a four-pole configuration (and fairly wide bandwidth (600 Hz for
CW) so there isn't much loss to begin with. When I turn on my NAR switch which
engages both the roofing filter and the INRAD 753 (which has a nominal
insertion loss of 9 dB), I see the s-meter go down about 1.5 "s" units.
"Surely it works in parallel with whatever filter is in N1 or N2 and doesn't
waste a slot. And if you want it always on, a simple diode should do the
trick."
The roofing filter operates on the signal input to the 9 MHz board, just after
the conversion to 9 MHz on the RF board. Thus it is acting in cascade with the
other 9 MHz filters downstream.
73,
Chuck NI0C
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