[Elecraft] KAT500 update

[Jim Brown]

On 12/8/2011 1:54 PM, Dick Lindzen wrote:
> Actually, it seems to me that an antenna tuner is needed because SWR
> is high, and if SWR is high, there are extra losses in the
> feedline.

The mismatch that affects feedline loss is the match between the antenna 
and the feedline. Thus, an antenna tuner reduces loss in the feedline 
ONLY if it is at the antenna end of the feedline. All the tuner in the 
shack does is make the rig happy, so that it can put full power into the 
line and not break.

>   The lowest cost low loss feeder is open line, and a
> balanced input to the tuner would be useful.

Virtually all the loss in transmission lines at HF (and even VHF) is due 
to copper (that is, I squared R). Open wire line (and window line) has 
much lower loss than coax because it has much higher impedance, so the 
current for the same transmit power is much less than for coax. That is, 
you're sending power on the line with more voltage and less current. 
It's still possible to have a lot of loss in window line or open wire 
line if there is a high SWR. One exception -- window line starts having 
significant dielectric loss when it is wet.

73, Jim K9YC