[Elecraft] Coax Loss Figures

[Tom W8JI]

> Well heck if LMR400 is .7dB/100ft I'm not so sure that its worth mucking
> with finding adapters for it as if I end up having to put 2 adapters on
> each end to get it to something I can use there goes most of my
> advantage of stepping up from LMR400 to LMR600...

 The loss in connectors or adaptors at HF or even up into VHF is virtually 
immeasurable, unless they are simply terrible. If the connectors are 
terrible you might have 0.05 dB loss.

A common SO-239/PL259 junction has less than .02 dB loss at upper HF.

I'd be more concerned with transmission line losses due to SWR on the 
transmission line and voltage breakdown of connectors in your application. 
Here are the peak voltages at the antenna base with only 100 watts applied 
at the antenna, and the losses in a feedline using 100 feet of LMR500:

160= 4800v  (>100:1 SWR) 16 dB feedline loss
80  = 1000v (>100:1 SWR) 6 dB feedline loss
40 =  215v (5.4:1 SWR)   .6 dB feedline loss
30 =  500v (26:1 SWR) 3 dB feedline loss
20 =  540v  (29:1 SWR)  3.5 dB feedline loss
15 =  280v (9:1 SWR)  1.7 dB feedline loss

Why would you worry about connectors when 100 feet of LMR500 would have 
losses like that? Put a tuner at the antenna base if you want to reduce 
losses.

73 Tom