How you define efficiency? If there¡¯s no loss, then an infinitely small antenna (a hertzian dipole, for instance) just has 1.5 dB gain over an isotropic antenna. Small antennas have low radiation resistance, but that only affects efficiency if there¡¯s loss.
For the run of the mill, nearly full sized, dipole, whether or not it¡¯s resonant doesn¡¯t change the radiation resistance much, neither does it change the loss resistance, so the efficiency doesn¡¯t change much.
What might change is the loss in the matching network or feedline.
The compact loop is notorious for having high loss because it has low radiation resistance compared to loss resistance. As is a mobile whip on 40 meters and down - they¡¯re a tiny fraction of a wavelength, so the radiation resistance is low.
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On Mar 4, 2024, at 1:01?PM, W0LEV <davearea51a@...> wrote:
?QUOTE (Jim Lux): .....short antennas have a different pattern than full
size antenna, but their "efficiency" isn't intrinsically different).
Jim, if we address small tuned loops on transmit, the efficiency over a
dipole radiator is considerably less, in round numbers, -20 dB.
In the limit of a point radiator (if it could radiate) - a true isotropic
source, the efficiency is zip, zero.
Dave - W?LEV
On Mon, Mar 4, 2024 at 7:28?PM Jim Lux <jimlux@...> wrote:
This is using resonance as a choke, not resonance of the entire antenna.
You want your choke to be high Z, so that currents don't flow on the
outside of the coax.
As far as the antenna goes, if you can drive it or couple power to/from
it, whether it's resonant or not makes no difference on the performance.
(aside from any other length related issues - short antennas have a
different pattern than full size antenna, but their "efficiency" isn't
intrinsically different).
-----Original Message-----
From: <[email protected]>
Sent: Mar 4, 2024 9:54 AM
To: <[email protected]>
Subject: Re: [nanovna-users] where is the end fed natural resonance
But then ARRL Antenna book says resonance has no affect on antenna
performance. Hams like to operate antennas at or near resonance as
that’s where drive point impedance is at its lowest value so
it’s easier to match,
Ray
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*Dave - W?LEV*
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Dave - W?LEV
