K2 KPA-100 5B, 5T & 5R

[Bob Towers]

I'm pretty sure I know what 5B, 5T & 5R do but what is the trigger, for instance, for setting 5T and 5B high and 5R low prior to transmitting with power over 11W? Is it band specific?

The reason for asking is that they're working correctly on 80m but not on 40-10m. They are working correctly in TEST mode on all bands, incidentally.

[Don Wilhelm-4]

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

Bob Towers wrote:
> I'm pretty sure I know what 5B, 5T & 5R do but what is the trigger, for
> instance, for setting 5T and 5B high and 5R low prior to transmitting with
> power over 11W? Is it band specific?
>
> The reason for asking is that they're working correctly on 80m but not on
> 40-10m. They are working correctly in TEST mode on all bands, incidentally.
>
>
>  
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[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


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