Posted by
Wes Stewart-2 on
Jul 17, 2020; 10:57pm
URL: http://elecraft.85.s1.nabble.com/Matching-resonant-antennas-tp7663149p7663318.html
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.pdfI'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/N7WSOn 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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