Don Wilhelm wrote:
Bob,

Those outputs are controlled by the firmware and as far as I know, they are not band dependent. If you have a band dependency on these signals, look for some other cause - RF in the shack perhaps? A problem with the AUXBUS signal? Is the 8R line from the base K2 being properly received by the KPA100? If the 5T and 5R signals are not correct, then look for a possible problem in the T/R switch. If you have an older KPA100, then the new (past year) T/R switch design should be installed (KPA100UPKT). Just how are they operating - you say only that they are not correct on 40 - 10 meters.

73,
Don W3FPR

Thanks for the quick reply.

RF in the shack is unlikely because I've only got as far as running the KPA-100 into a dummy load. The indicated and measured SWR doesn't get worse than 1.1:1 on all bands.

The fact that it works up to 100W on 80m tends to rule out an 8R problem. I have noticed that 8R (U1-27) is around 1.22V on 80m (over 11W) and 1.69V on 40 - 10m. Is this significant?

Is the AUXBUS signal band dependent? Is the AUXBUS the signal which initiates the switching of the appropriate LPF relays in the K2 and the the KPA-100?

5T (and 5B) should go high when the KPA-100 operates over 11W; conversely 5R should go low. It only happens this way on 80m. On 40-10m over 11W, 5T and 5B remain low (0.0V) and 5R stays high, so the KPA-100 doesn't switch into high power mode.

The KPA-100 is less than 6 months old.

73
Bob MM0RKT


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