[Elecraft] OT: pwr rating of RG6, etc

[Don Wilhelm]

You use it because of 2 characteristics.  1) It has lower loss than an 
equal physical size 50 ohm cable - and that is true even considering the 
added loss due to mismatch.  2) It is conviently available and inexpensive.

Considering the added loss due to a 1.5 SWR, look at the charts.  If the 
matched line loss is 2 dB, the loss when the SWR is 1.5 is only 2.1 dB.  
Even if the matched line loss is 10 dB, having an SWR of 1.5 adds only 
0.2 dB to the total loss.  A 1.5 SWR is insignificant when considering 
line loss, especially at HF.

The facts do not support the popular view that an SWR any higher than 
1.0 is a bad thing.  In most cases, a transmission line SWR of 2.0 or 
below will work fine.

Now, there is another part to consider - the feedpoint impedance at the 
output of a transceiver may have to be transformed to something closer 
to 50 ohms for proper, full power operation of the PA - but that is the 
job of a tuner, it has nothing to do with feedline loss beyond the 
tuner.  Unfortunately, these two parameters get mixed together and the 
result is 'numerical soup'.


73,
Don W3FPR

Samuel Strongin wrote:
> RG6 is 75 ohm cable. Why would you buy a great radio and worry about 
> performance,then go use the wrong cable. You start out at a 1.5:1 swr. 
> Idon't get it.
>                  kf4yox
>