[PPRAANet] transmission line question

[K3ILC]

First of all, 120 feet of RG8X is very lossy at 144 MHz.
For a 1:1 SWR at the antenna, the loss is 4.863 db for Belden RG8X. For 
100 watts in, you'll get 32.639 watts out.
For a 3:1 SWR at the antenna, the loss is 4.863 db plus an SWR loss of 
1.132 db for a total of 5.995 db.

For 50 feet of LMR at 1:1 SWR, the loss is only .743 db. For 100 watts 
in you'll get 84.273 watts out.

I used https://www.qsl.net/co8tw/Coax_Calculator.htm to produce these 
numbers.

I think two things are going on here:

1.  120 feet of RG8X is so long and lossy, that it's starting to act 
more like a dummy load (resistive), so the SWR appears better.
2. With 50 feet of LMR 400 equivalent, the losses are much less, and 
what you're SWR meter is reading is representative of a higher SWR at 
the antenna.  With a higher SWR, you'll have standing waves along the 
coax.  So the SWR would actually vary with meaaurements with different 
lengths of coax.  To measure the true SWR of the antenna, you would have 
to measure it at the antenna itself.

Despite the SWR situation, you'll get more power to the antenna using 
the LMR 400.

That's my guess.

Jim Madsen
K3ILC