[Elecraft] K2 KPA-100 5B, 5T & 5R

[Bob Towers]

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