[Elecraft] K3 Internal Tuner Question

[Tom Azlin N4ZPT]

Not sure I understand this.

I did not think an SWR meter was supposed to work properly only when 
seeing 50 ohms restive.

If the line is not flat it is terminated in to something other than the 
feedline impedance, i.e. not 50 ohms restive in this discussion. I would 
expect the SWR meter at some point in the feedline to be accurate under 
those conditions because it is supposed to measure the standing wave 
ratio of the feedline with respect to that 50 ohm resistive.

If I then have an antenna coupler in the radio that is matching the 
transmitter to that non-50 ohm impedance why would the SWR meter change 
to inaccurately measuring the SWR?   Putting the K3 into bypass or 
letting it "tune" should not change the SWR measures at some point in 
the feedline. The K3 may show 1:1 simply because it properly transformed 
the line impedance to 50 ohms restive.

Perhaps I am missing something here. Sorry for continuing the discussion.

73, tom n4zpt

On 1/2/2012 8:06 PM, Rick Bates wrote:
> Let me see if I can correctly state, with clarity for all to understand so
> this thread can die peacefully and we can move on (please?).
>
> The K3 puts out power into an internal tuner (if installed) and then to an
> SO-239 at the rear of the radio.  If the tuner is in bypass, the impedance
> is very close to 50 ohm resistive at that connector.  In this case, any SWR
> meter (bridge) downstream to the antenna will read the SWR (AT THAT POINT IN
> THE FEEDLINE which may/not agree with the K3 reading).
>
> If the tuner is NOT in bypass, the impedance at the same SO-239 will be
> +-10:1 of 50 ohms.  Since any other SWR meter (bridge) between the K3 and
> the antenna is probably NOT seeing the expected 50 Ohm impedance, the
> reading of OTHER than the K3 meter will be called into question and more
> than likely wrong.
>
> Repeating, when the internal tuner is used, the K3 meter is the only one
> that is accurate.
>
> Thank you and Happy New Year,
> Rick wa6nhc