I can confirm this behavior, the 60m filter seens to kick for a much a wider frequency range than the 60m band itself and considerably down on the filter flank. I wonder if the other ham band filters also covers an excessively wide frequency band in an attempt to give radios without the KBPF3 some general frequancy coverage. On higher frquencie that could be a problem. I just tested the 15m band and judging from the clicks from the radio that filter seems to cover 20.9-21.51MHz with no change in sensitivity on the boundary. So that's looks good. So why is the 60m filter engaged for so wide a band? The international differences for the band are not that big - they are all within the 5260-5400 range.

AB2TC - Knut

--- In Elecraft_K3@..., "wa9fvp" <willcoele@...> wrote:

With the KBPF3 installed, I notice that when I tune from 5.510 to 5.5099 the sensitivity drops. It picks up when I tune down to the 60 meter bands and rolls off again when I reach 5.250. At 5.2499 the sensitivity is back to normal. When my SDR-14 is connected to the I.F. output, with a 1 MHz span, I can see that the 60 meter BPF has a band pass from about 5.08 to 5.46 MHz.

Normally this isn't a problem. I can turn on the preamp to compensate for the loss but when I tune within the 60 meter band, I'm constantly switching the preamp on and off. With the preamp on above 5.5099 and below 5.25, it overloads the SDR-14. Above and below the 60 meter band filter, looking at the SDR-14 spectrum, I can see that the General coverage filters are flat.

I like to listen to the aircraft frequencies between 5 and 6 MHz but the loss in sensitivity, when the 60 meter band filter is switched in, is annoying. Is there a way to defeat this or modify the filter switching limits?

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