My post refers to tuned
(inductance-capacitance) circuits.? Properly constructed, a spiral
loop will have a bandwidth (-6 db) of just a few kHz at lower SW
frequencies.? The Q is extremely high, adjacent QRM and local
noise significantly mitigated.
Bob C.
On 4/25/2022 6:04 PM, ED MONTAIGNE
wrote:
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Remember that flat spiral antennas are very wide
band ant that means low Q which equals more QRM/QRN. Narrow band
means High Q and low noise.
I have been using spiral loops
exclusively for reception of LW, MW, and SW many years.? I
understand, despite their low radiation resistance, loops
have become quite popular for transmission experimentation
among hams in recent years.
The spiral geometry provides minimum distributed
capacitance in a coil.? This leads to the possibility of a
higher L/C ratio in a resonant circuit and greater
sensitivity.? All my antennas are resonant primary
circuits transformer coupled through a low-impedance coil
and twisted pair to the receiver.? The secondary
(coupling) loop must provide a good impedance match to the
transmission line and have a suitable coefficient of
coupling with the primary circuit.
My current articles in the files section are as follows:
PRTC Loop Antenna - 2022_02_14.pdf is a 3' diagonal
spiral covering 2.6 to 12.1 MHz.
Electrically Small Resonant Loop for Shortwave (Oct
'14).pdf is a 2' diagonal version covering
approximately the same band of frequencies.
Electrically Small Resonant Loop Antenna for Mediumwave
Reception.pdf is the current draft of my MW article,
which identifies a lot of my engineering sources, theory,
and construction details.
Hope some of this is helpful.
Bob C.
Dexter