[Elecraft] K3 - Numeric SWR Display

[Ron D'Eau Claire]

Excellent point Joe. 

The current QST magazine that features a short article about running open
wire or window line to coax outside the house and then using a short length
of coax to reach the rig. The author noted that with a short run of 10 feet
of the coax he uses, the losses with a 10:1 SWR would be about 1 dB at 28
MHz. 

That sounds good assuming the coax losses and SWR are really that low in
worst case. But what he missed was that he used a "choke balun" between the
coax and feed line that consists of an additional 22 feet of coax wound up
in a coil to keep RF off of the outside of the coax shield and so out of the
shack. 

So he really has 32 feet of coax between the rig and the open wire feed
line. If he original assumptions about maximum SWR and losses were correct,
he's really losing about half of his transmitter power (3 dB) in that coax
link and balun.

Ron  

-----Original Message-----

>       Alternately, feeding through one or more half-waves of
> coax will give you good accuracy while letting you get far 
> enough away from the antenna to not affect the measurement.

Only if the feedline has zero loss.  Force 12 are known for 
making their antennas "look better" by specifying the SWR 
through 100 feet of feedline.