I also had a problem with high insertion loss
in a TT217 250 Hz filter. Mine turned out to have 8 dB
more insertion loss than normal.
If you have a steady signal source, and
properly working filters, here are the "approximate"
readings you should see. Remember to set DSP =
2000 and do not change it during these checks.
1000 Hz = S9 (reference should be set in this area)
500 Hz = ~S9+6 dB (check with 6 dB ATTN in Orion)
250 Hz = S9
As discussed before, the 500/250 Hz filters have
an additional 12 dB amplifier to compensate for
their increased insertion loss. The 500 Hz filter
has ~6 dB insertion loss, therefore it will appear to
have 6 dB gain. If the 250 Hz is working properly, it
will have ~12 dB insertion loss which is exactly
compensated for by the 12 dB amplifier. My first
TT217 had 19.5 dB insertion loss and the good one
had 11.5 dB loss.
73, Bill W4ZV
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