Topband: Ladder line vs coax loss epiphany

[Shoppa, Tim]

It took me literally decades to realize this, but the low ladder line losses that show up in the ARRL graphs are not because ladder line is magical. I had been reading many articles in QST, and on the web, that made it seem like ladder line was magical this way. Really, for decades I did not understand why ladder line had so much less loss than comparable-copper coax.

It's because ladder line is used at 450 or 600 ohm impedance, so it of course has one tenth the resistive losses of 50 ohm coax built with similar amount of copper.

There a similar (but smaller) advantage to 75 ohm coax vs 52 ohm coax.

Tim N3QE

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Kenneth Silverman
Sent: Tuesday, April 29, 2014 11:00 AM
To: topband at contesting.com
Subject: Re: Topband: 1000 feet 5/8" hardline or 600ohm True Ladder lin

Rune,

Back in 1997 N6BV and I did some testing using "ladder line" (not the real
600 ohm stuff) and some 9:1 baluns on each end.  We were looking at a site in YV where the beach was about 1000' from the hotel room. We tested the
following:
- loss in back to back baluns
- loss in 100' of ladder line and baluns on each end

We tested 160 to 10m.  We lost the data but I seem to remember the total loss on 80/160 with 1000' of line was negligible.  Maybe in the 2 dB range on 10m with 1000' of ladder line.

A few of us went to the YV location to run the IARU contest with the 1000'
run of ladder line, using a single vertical on the beach.  The system worked well, except when there was rain (varying SWR), or coconuts and palm fronds fell and broke the line.

I just talked to N6BV and he said the ARRL Labratory recently did some careful measurements on matched-line losses for open-wire line for input to Dean's TLW program.  There is a new executable that contains the algorithms for loss computation.

Good luck, Kenny K2KW
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