[CQ-Contest] band-pass filtering -- a new approach?

[Pete Smith]

I've been researching band-pass filtering for SO2R, and it has occurred to
me to try a different approach if the peer review sounds favorable.

What I'm planning is to build a box for each of my transceivers, containing
a receiver protection circuit (diodes and a resistor), receive-level
bandpass filters and a relay switching matrix to select the filters AND
bypass them on transmit.  This would seem to offer several advantages --

I can use W3LPL's 3-pole receive filter circuit, which uses standard cap
values and delivers performance that is probably superior to any commercial
alternative except for W3NQN's expensive transmit filters.

I avoid issues with burning out the filter components from transmit power,
particularly with a messy amplifier input SWR on some bands.

I avoid the reduction in drive to my SB-220, which really needs its 120 watts.

I can be fairly relaxed about the physical layout, since SWR is not the
issue it is on the transmit side.

I realize that having a bandpass filter on the transmit side offers
advantages too, in particular reducing harmonic output and wideband noise.
But on balance, this seems like a good idea, plus it'll give me a project
for the winter.  Comments? 

73, Pete N4ZR
www.qsl.net/n4zr


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