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
On 7/17/2020 1:47 PM, Edward R Cole wrote:
Interesting discussion:
But most of us probably tune our antennas for best SWR at the desired
frequency.
I have a dual-band 80-40m inverted-V with apex at 40-foot and 80m wire
tail at 20-foot. The separate 40m wire is spaced 6-inches from the
80m wire with wooden dowels. I found by trial-n-error that one must
tune the lowest frequency wires, first. I did that using an antenna
analyzer. Then the 40m wires. Turns out (probably due to coupling)
that the 40m antenna is narrow bw (50-KHz at best) whereas I get good
SWR from 3650-4000 KHz.
The purist will say that's not resonant but the transmitter is happy.
I can run bypass on 3800-4000 KHz with my KXPA100/KXAT100 but must
tune using the atu on 40m.
For working around Alaska (out to 800-miles) this "cloud burner" works
well with 100w. I only use SSB on these bands. 3920 is the defacto
calling/emcomm channel in AK.
When we have an earthquake, 3920 lights up (as well as 14,292) for
reporting from our remote areas. I live two miles from salt-water so
tsunami watch is common after a "big one".
73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
dubus...@gmail.com
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