[Elecraft] K3 SWR Accuracy - reprise

[Ron D'Eau Claire]

I've noticed that too, but never though much of it since the external meter
and the K3 agree at 1:1. 

Above 1:1, the K3's SWR indication reads lower than the external meter at
100 watts on the lower frequency bands (80, 160) but agrees well with the
external meter on the higher frequency bands. The K3 and external meters
agree well at 10 watts on all bands. 

For example, I set up my external tuner for an SWR of 1.6:1 on the external
meter and transmit 10 watts on 80 M and the K3 agrees with the external
meter just fine, but if I crank up the POWER while in tune I'll see the SWR
indicated on the K3 drop to 1.0:1 when the KPA100 kicks in. At 100 watts
out, the K3 indicates 1.1:1 while the external meter indicates 1.6:1 at all
times. 

Adjusting the tuner for minimum SWR brings its meter and the K3 down to an
indicated 1:1. 

I have about 18 inches of cable between the tuner and the K3. If it was
going to have a significant effect, I'd expect it to show up on the higher
frequencies, not the lower frequencies. Besides, all is well at 10 watts on
all bands.

It's a non-issue to me since all I care about is knowing I have the antenna
system well matched to the K3. 

Ron AC7AC

 
-----Original Message-----
What power level were you using? And what type of external bridge?

The K3's SWR bridge has two sensitivity ranges. If you have power set  
to 12 W or lower, the higher-sensitivity range is used. If you have  
power set above 12 W, the lower-sensitivity range is used. This is  
necessary to prevent heating of the transformers in the bridge.

SWR accuracy will be best when you're in the upper part of each range.  
So, for example, it'll be more accurate at 12 W than 1 W, and more  
accurate at 100 W than at 13 W. But accuracy should still be  
reasonable even in the lower end of the range.

Your external bridge may have better sensitivity at the particular  
power range you were using.

73,
Wayne
N6KR


On Nov 4, 2009, at 9:13 AM, DM4iM wrote:

> I don't have the KAT3, i use an external homemade tuner and a cheap
> swr-meter between it and the K3. Don't know how accurate the swr-meter
> is, but i notice that the K3 shows 1.1:1 while the external meter  
> still
> reads worse. Fiddling with the controls of the tuner settles the  
> needle
> on the external meter, while the readout on the K3's display stays
> unchanged.
> I posted this to the list some weeks ago, but nobody noticed.
>
> -- 
>
> 73, DM4iM
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