[Elecraft] [K3] - Odd SWR readings ANT1 v ANT2

[Joe Subich, W4TV]

Stewart,

The K3ANT does not do a "hard" bypass.  Instead it sets the
tuner to the memorized 50 Ohm : 50 Ohm position.

Since the tuner memories are "by band" and "by antenna" - plug
the dummy load into the ANT 1 position, enable the tuner and
hit the "ATU Tune" button.  That will "teach" the tuner the 50
Ohm setting for ANT 1 and you won't see the issue in the future.

73,

    ... Joe, W4TV

On 6/11/2010 2:14 PM, Stewart Rolfe wrote:
> No doubt the recent Es propagation has brought the following
> behaviour to my attention...it's only evident on 10m for some
> reason:- Screw in a PL259 type dummy load into ANT1 (KAT3) and
> deselect ATU. Press TUNE (10w) and the indicated swr on the K3 is 1.7
> to 1.8. Change dummy load to ANT2 and select and the indicated swr is
> now 1.0...! I've swapped the antenna leads on the KAT3 board to
> determine it's something to do with circuitry around the antenna
> relay and not PL259 sockets/interconnecting leads but according to
> the schematics each path is equivalent. Furthermore an external swr
> meter placed between dummy load and K3 indicates 1:1 on *both* ANT 1
> and 2 so it seems to be  something to do with the way the radio is
> sensing the swr between the two antenna sockets. I'm not at all hung
> up on swr but why the difference between the 2 antenna inputs -
> strays in the relay or surge arrestors? It also looks like the radio
> is 'thinking' about the power output when the swr indicates 1:1.8 and
> above and may cause power variations....? Thoughts?? 73, Stewart
> Rolfe, GW0ETF (K3 #145)
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