Date: Tue, 20 Dec 2016 12:17:34 -0500
From: "john@kk9a.com" <john@kk9a.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Double Coax Runs to Reduce Loss?
It sounds like it work, at least until you do the math. Each run still has
the same dB/ft loss.
John KK9A
## Assuming lossless xfmrs at each end. Loss in each coax run is identical.
Total system loss is the same as a single coax..and no transformers.
## IE: 2 x 300 ft runs of 213 in parallel on 10m. Assume 3 db loss per
coax. Stuff 1 kw into the lossless xfmr... and u now have 500w into each coax.
Each coax has 3 db loss... so only 250w at each end of each coax.
250+250 = 500w. Which is no different vs 1 kw into a single coax..with the
same 3 db of loss, still = 500w. Maths are the same on TX...and also RX.
## However 2 x coaxs in parallel will indeed handle double the TX power.
## If this is for monoband use, a simple L network at each end will easily
do the
50:25............ and 25: 50 ohm transformation...with virtually no losses.
## Lossless L networks are typ made with cu tubing + NPO doorknob caps.
That scheme works good for feeding 2....or 3 or 4 monoband yagis.
## But for greater power handling capability.. just use bigger coax to begin
with,
then you also get the benefit of lower loss coax. Lower loss coax is the ticket
for both RX + TX.....esp on long runs .
Jim VE7RF
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