K1 Filter Board Alignments

I have hooked up the FT-817 to a dummy load in order to perform the receiver tests on the K1. The first tests consist of aligning the trimmer capacitors on the filter board. To begin with I used the DL-1 dummy load.

I have been able to peak the signals on all four bands but:

  • CF (30m) has maximum when it is fully open.
  • CM (40m) seemed to have a minimum instead of maximum around half-way open, thus it had maximum both when fully open and when fully closed.

I have tried to reduce the signal strength by removing the antenna wire, but I got the same result. Furthermore,the signals got much stronger when I put my finger ion the vicinity of the filter board. does it mean that it could use som extra capacitance? Or the opposite?

Then I tried to use the XG-2 signal generator with which I was able to find a peak on CH and could actually hear the 1 uV signal, but CF was still fully open.
On 20m I could hear the 1uV signal from the XG-2 even with the attenuator switched ON! Once issue that I came to think of was that the XG-2 frequencies do not lie in the middle of the desired band and so what if the filter width will not be adequate if I do the alignments in the top of 40m and 20m. Well, on the other hand, the K1 has been designed to have either 80 kHz or 150 kHz of band coverage, so the filters must be wide enough for the entire 80 kHz.

Tomorrow I wil try to re-do the alignments using a weaker signal and maybe I should try to use my scopes?

Author: Alexandru Csete

Embedded software engineer in the satcom industry during the day. Radio amateur and SDR hacker during the night.