Now to report back on what I found out concerning my OHR 500 IF filter: I decided to look at the bandpass visually using my laptop computer and my digital mode program, HamScope . This is a good way to see what you are hearing, even with a CW transceiver.

I found that the displayed "lighted" bandpass on the waterfall, extended from about 400 Hz up to 1400 or 1500 Hz. It was then that I realized the original owner / builder from whom I bought the rig, chose a rather odd placement of the BFO injection frequency. It was on the correct side of the IF bandpass, but was too far above it in frequency. So using the manual to guide me, I retuned the BFO about 400 Hz closer to the filter's passband.

Wow, now anything above about 1100 Hz was severely attenuated, and the CW I was listening to, was much easier to copy, and there was far less QRM able to reach the headphones. I also noted that now I was NOT able to hear any signals on the wrong sideband as I did before (albeit faintly). The manual instructs the builder to tune in a signal to the center of the dial and adjust the trim capacitor C231 to obtain a 600 or 700 Hz note. It appears that doing this by ear can result in a faulty placement of the BFO injection frequency. Using PSK software could help homebrewers "see" what they are dong with the IF, BFO, etc., more clearly. Now, finally, I see why the brilliant designers of Elecraft gear instruct builders to use their software program to align their rigs. Sorry I was so slow on the uptake concerning my perceived problem. I am really happy this turned out like it did.

72,
Jerry KD0CA