[Elecraft] Internal K3 SWR vs Extermal SWR Meter

[Don Wilhelm]

Mark,

There is good reason (assuming the internal tuner in the K3) for *not* 
syncing the wattmeters.
With the KAT3 in-line, the SWR is *not* reading the SWR on the feedline, 
but instead telling you the SWR at the *input* to the KAT3 - that is the 
load that the K3 PA sees, and that is what really matters for full power 
output.  Remember too that the KAT3 will have some residual reactance 
even in bypass mode.  That will also make a difference in the SWR seen 
by the K3 PA transistors and the SWR on the feedline - it is just one of 
"those things".  A 1.4 SWR on the feedline may actually result in a 1.1 
SWR at the other end of that residual reactance.

The external wattmeter will indicate the SWR on the feedline - at the 
output of the KAT3.  There is nothing the KAT3 can do to change that.

In addition, many wattmeters are woefully inaccurate when reading SWR.  
Most All will be quite accurate for an SWR of 1.0, but at anything other 
than that, you will find a variation in the readings on amateur grade 
wattmeters.

If you have a good dummy load (non-reactive 50 ohms), you can calibrate 
the K3 wattmeter (for power, not SWR).  The procedure is in the 
Calibration section of the manual.

73,
Don W3FPR

On 11/17/2013 4:57 PM, pastormg2 at verizon.net wrote:
> John, the problem is that I don't have one of these. But thanks for the suggestion. One thing I have not tried is hooking up my antenna and external wattmeter coupler with Antenna 2 instead of Antenna 1. I am anxious to find out if I get the same readings with #2 as I did with #1. I guess I am rather perplexed at the thought that there is such a variance between the K3 wattmeter vs an external wattmeter. Especially, when I connected the coupler to the antenna #1 with a plug and then attached the antenna coax to the coupler. It's a shame that the K3 does not have a way of synching up the internal wattmeter with an external wattmeter. Hopefully somebody from elecraft will read this email and make a comment on it. Thanks to all with their responses. Mark Griffin, KB3Z
>