I wrote about some of this in my paper ARRL Antenna Compendium paper on ladder
line 20 years ago. https://sadxa.org/n7ws/Ladder_Line.pdf
I've seen pictures of those SW transmitting plants and always assumed that they
must have been very efficient. Upon reflection---no pun intended---now I'm not
so sure. If losses mounted up, (which they most certainly did at 14:1 SWR) they
had the option of just turning up the wick.
Furthermore, as I said in closing: "Contrary to the conventional wisdom, ladder
line is not a panacea for every transmission line problem." In the ensuing 20
years, I've become even more convinced of this. When tuner and balun losses are
factored into this picture I don't know why anyone would want to use this
stuff. I sure don't.
I have a KAT500 and use it to tune some way-off resonant antennas (fed with 7/8"
Heliax) but I don't delude myself into thinking "I've contained system losses."
Wes N7WS
https://www.qrz.com/db/N7WS
On 7/17/2020 2:32 PM, Barry LaZar wrote:
Resonance is over rated. The problem of believing you must have a resonant
antenna arose with the use of coax cable began. High SWRs causes high system
losses.
Prior to the widespread use of coax, open wire was used and few antenna
systems were really resonant, and nor were they reflecting a 1:1 SWR. Back
then, no one cared as tubes were used and pi-net or swinging links were used
to match to whatever was connected to the transmitter. In fact, I once visited
a site that used rhombic antennas and Sterba curtains being fed by high power
transmitters. The feed line were copper pipes about 1/4" in diameter and
spaced about 4". The SWR, I was told, was 14:1. I asked if that was a problem
of transferring energy to the system. The answer was no as the final output
stage could match it and the system losses were low due to the type of feed
line used. This was a lesson I learned 60 years ago and haven't forgotten it.
The site was the RCA site the once stood on Montauck Point on Long Island, New
York.
One point that keeps getting forgotten is the conservation of energy concept.
What that means is energy can only be changed and not lost. Typically that
means transmitter energy would be changed to heat, but not lost. What is not
changed to heat on the coax will make it to the antenna where it MUST be
radiated and not lost. Yhe practical application of this is use really good
coax if you can't get to a 1:1-2:1 SWR, ot there about. Alternatively, use
ladder line and a current balun. Elecraft tuners easily tune 10:1 SWR which
contains system losses nicely. I have been doing this for a very long time and
have achieved WAS, DXCC phone, DXCC CW, and DXCC digital, and, I'm 13 short on
80 of making 5BDXCC.
73,
Barry
K3NDM
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