D19 shorting out in K1

[Jim Ragsdale]

I've been wondering if anyone else has experienced this. I have a K1
with the KAT1 ATU and am using an A/B switch to swap antennas. Three
times now when I swap antennas with the power on the K1, it shorts out
diode D19 in the final. I can solve the problem by always powering down
before the swap, but sometimes I forget to do that (has nothing do with
my age. HI).

Any thoughts?

73, Jim W5LA

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[Greg Troxel-2]

Jim Ragsdale <[hidden email]> writes:

> I've been wondering if anyone else has experienced this. I have a K1
> with the KAT1 ATU and am using an A/B switch to swap antennas. Three
> times now when I swap antennas with the power on the K1, it shorts out
> diode D19 in the final. I can solve the problem by always powering
> down before the swap, but sometimes I forget to do that (has nothing
> do with my age. HI).
>
> Any thoughts?

Are you really sure there is no electrostatic charge on the antenna you
are switching to?  Do you have a bleeder resistor, or does the switch
ground the unused antenna?

73 de n1dam
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[Don Wilhelm]

Jim,

D19 is intended to sacrifice itself instead of the PA transistor from
events like high SWR or power supply surges.

That means your antenna switching is likely producing a voltage spike
when switching.

Possibilities that I can think of include switching an antenna which has
a bias T network associated with it, or somehow your power supply is
producing a spike when you switch the antenna.

There is nothing in the K1 itself which would cause it (unless the K1 is
transmitting when the antenna is switched).

73,
Don W3FPR

On 3/12/2018 8:08 AM, Jim Ragsdale wrote:
> I've been wondering if anyone else has experienced this. I have a K1
> with the KAT1 ATU and am using an A/B switch to swap antennas. Three
> times now when I swap antennas with the power on the K1, it shorts out
> diode D19 in the final. I can solve the problem by always powering down
> before the swap, but sometimes I forget to do that (has nothing do with
> my age. HI).
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