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[email protected] · October 12th 14, 08:21 PM posted to rec.radio.amateur.antenna

John S wrote:
On 10/11/2014 12:51 PM, wrote:
John S wrote:

snip

OK, so lets analyze my results:

Conditions are free space, wire is #14 gauge but may have zero ohms
where noted. The antenna is a dipole with the source connected at the
center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna
resonance plays no part in this. # segments = 99 unless otherwise noted.

Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency

0.5 zero 80 0 2.16 100%
0.5 #14 73.6 -.09 2.08 98%

0.25 zero 13.2 0 1.85 100%
0.25 #14 13.7 -.17 1.69 96%

0.125 zero 3 0 1.78 100%
0.125 #14 3.25 -.33 1.45 93%

0.05 zero .464 0 1.76 100%
0.05 #14 .556 -.78 0.98 83%

Rin is the terminal resistance only. Gave is the average gain integrated
over the pattern, Gmax is the highest gain detected.

Unless I have done something wrong, I see that a dipole that is .05
wavelengths long is within 20% of being as efficient as a half-wave
dipole. Even including wire resistance.

I invite discussion in any case.

The diameter of #14 solid wire is 0.0641"; how about a line for #8, which
is 0.1285"?

0.05 #8 0.515 -.41 1.36 91.1%

Free space, no ground loss.

So it seems that a .05 lamda dipole is only about 7% less efficient than
a full size dipole wit suitable wire...

So much for "short antennas are not efficient".

Now, if we could just invent room temperature superconductor wire and
lossles toroids we could match the thing to a 50 Ohm system...

--
Jim Pennino

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