[Elecraft] K3 Power Reading/SWR/ALC Problem

[ab2tc]

Hi Don and all,

I really don't understand why static build up on the antenna should be a
problem with the K3. Due to the (good) design of the SWR bridge (a two
transformer design with a voltage transformer right across the output) the
antenna port presents a dead short circuit at DC both in receive and
transmit. I just verified this with an ohm-meter (in receive only - no need
to check in transmit since the SWR bridge is surely present then - don't
want to kill my DMM).

Maybe we are talking semantics here but it appears to me that the cause of
diode damage in the SWR bridge circuit is more likely caused by transients
induced into the antenna system by nearby lightning strikes than static
buildup. 

Knut - AB2TC


Don Wilhelm wrote
> Paul,
> 
> The diodes are the most likely suspect, so replace them first and
> re-check.
> 
> You are correct that the problem is that the wattmeter is not feeding 
> the power back to the MCU and the power becomes uncontrolled.
> 
> Wattmeter damage is normally a result of static coming in on the antenna 
> feedline.  If you do not have an means of disconnecting the antenna when 
> not in use, it would be wise to add that - switching the K3 to a dummy 
> load would be a good addition too.
> 
> 73,
> Don W3FPR
> <snip>





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