[Elecraft] [KX3] SWR Reading Instability Follow-up

[Don Wilhelm]

Mark's analysis was 'right on'.  Due to the varying nature of the SSB RF 
waveform and the workings of digital sampling, it is impossible for the 
forward power and reverse power to be sampled at exactly the same 
instant (one of the limitations of digital sampling intervals).
So, if the reverse power happens to be sampled at a time the RF is high, 
and the forward power is sampled when the RF is low, a higher SWR than 
actually exists will be computed (and displayed).

The solution is to check the SWR when in TUNE (set TUN PWR to a sane 
value) and adjust the Alexloop using that input and SWR indication. Then 
when operating SSB, either ignore the SWR indication or switch to 
display ALC and Compression which should be more meaningful.

73,
Don W3FPR

On 4/10/2014 4:56 PM, VaibhaV Sharma wrote:
> Thanks for repeating the tests.
>
> I started paying close attention to the SWR meter after I got the Alex
> Loop. The antenna has a very narrow window where the SWR is low (receive
> noise high). I try not to use the ATU with the loop. Even touching the loop
> capacitor dial changes its behavior and it is often hard to calibrate it
> for a low SWR while watching the SWR meter.
>
> The KX3 SWR indication hopefully is only a UI issue. Is there a way to
> stream SWR and other data off the radio so one can watch what the radio
> sees?
>