[TenTec] G5RV

Steve Hunt steve at karinya.net
Sun Feb 1 15:50:19 EST 2009


Yes, I'm sure. According to the VK1OD on-line calculator, at 3.8 MHz 
100m of RG213 with 14-j1 as a load has a loss of 1.9dB; 100m of Wireman 
551 with 14-j1 as the load has a loss of 3.1dB. I'm not saying the 
difference is particularly significant - I'm just pointing out that 
ladderline is not always lower loss than coax - it depends on the load 

Incidentally, be wary of those ARRL charts which tell you what the 
"excess loss" is for a particular VSWR - they are approximations. There 
are some particular situations where a 1:1 VSWR produces more loss than 
with a higher VSWR. here's an example:

Take 15ft of RG213 with a load of 100+j100. At  3.8 MHz the loss with 
this 4.3:1 VSWR is 0.025dB, whereas the matched loss is over twice this 
at 0.055dB. I know these are ridiculously small losses, but I'm just 
illustrating the fallacy of thinking you can add a fixed "extra loss" 
figure for some particular VSWR value.

Steve G3TXQ

Dr. Gerald N. Johnson wrote:
> Are you sure? Using data and formulae in the 1994 ARRL Antenna Book, I
> see 100' of RG213 has 0.6 dB loss at 4 MHz when matched, and 1.066 dB
> with a 3.6:1 SWR. 1" spaced window line has 0.027 dB (had to stretch the
> loss chart by a factor of ten for that line) per 100' matched and 0.41
> dB loss with the SWR of 32:1.

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