Topband: Transmit High Pass Filters for BCB Interference

[k3ky at radioprism.com]

I bought a DLW Associates FL1718 filter and have been completely
happy with that choice. I got mine direct from Doug Williams
because I wanted a custom filter with one of the notches centered
right on the broadcaster's frequency. Specs say >90dB attenuation
at that notch frequency. I was willing to accept a slightly less
steep rejection skirt in order to get that optimized notch.

http://www.dlwc.com/

I just ran a daytime check with my filter in and out of the line.
My local BCB flamethrower indicates 50dB over S9 on my FT-1000D.
Inserting the filter drops the S-meter reading to S2. Assuming
5dB per S unit, this is -85dB indicated- and this is without any
special measures such as a better (low inductance) station ground
or any inline chokes. Such measures should improve the ultimate
rejection a little more. The broadcaster drops power considerably
at night, and is then only faintly audible in my receiver with no
S-meter deflection at all.

The right location for such a high pass filter is between your
Rx/Tx and any power amplifier- unless the transceiver happens to
have unusually high transmitter power exceeding 200W.

If I had to make this buying decision again I would buy this
model again without hesitation. It's an amazingly effective
filter, good for up to 200W on transmit. I wish the local
broadcaster had paid for my filter, too- HI!

73, David K3KY