[TowerTalk] (parallel) Coax Loss

[john at kk9a.com]

It's 5dB per 100 feet so 200 feet has 10dB loss.  This is why coax choice is 
important for long runs.

I wonder what happens if you run two parallel coax lines.  Lets say we are 
using your coax and have 10dB loss in 200 feet.  If I run 200 watts to it, 
I'll have 20 watts at the antenna.  If I run two 200 foot parallel coax 
lines (and match the impedance at each end)  I am feeding each coax with 100 
watts and have 10 watts (10dB loss) at the end which combines to 20 watts at 
the antenna.   Is there really no advantage to having the additional coax 
cable?  A more practical example of this is having a stack of beams and 
running coax from each one to the shack, vs a single feedline to the tower 
and then split to each antenna.

John KK9A



Subject: [TowerTalk] Coax Loss
From: "Jim Miller KG0KP" <JimMiller at STL-OnLine.Net>
Reply-to: "Tower and HF antenna construction topics." 
<towertalk at contesting.com>
Date: Thu, 4 Feb 2010 10:38:27 -0600


I have struggled with this and have seen it both ways.

Take an example of 100 feet of some coax at 5 db loss.
Is the loss at 200 feet 8 db or is it 10 db ????
And is the loss at 50 feet 2 db or 2.5 db ????

Thanks,
73, Jim