Re: NEC-LIST: Loopstick data?

Hello Doug

A few references on loopsticks:

Burton, King & Wu, "The loop antenna with cylindrical core",
IEEE Trans AP-31, March 1983,

Przedpelski, "Loop antenna design", RF Design, Nov./Dec. 1982,

Schemel, "The loop aerial revived", Wireless World, July 1979,

Everden, "Ferrite rod aerials", Wireless World, Sep. 1954.

Basically the ferrite increases the effective area of the coil by
a factor called the effective mu, which depends more on the
length-to-diameter ratio of the stick than on its actual bulk mu
(relative permeability). A value of 50 is typical for common
rods with L/D=10.

The antennas need to be tuned and it is common to parallel tune
them and connect direct to a FET voltage follower with a low output
impedance into the receiver. You need to get ferrite of the
appropriate grade for the frequency in use. Loopsticks work fine
for AM reception where there is plenty of signal, but to get
sensitivity down to the external noise level a loop with at
least 1 sq. inch c/s area is necessary below 1.6 MHz.

The number of turns needed on a typical core is approximately
(10000 to 20000)/F with F in kHz if you have an ordinary
broadcast-type variable capacitor for tuning it.

Loopsticks are never used for transmitting because their radiation
efficiency is extremely low, and hysteresis in the material makes
it even lower. They only work for reception because the external
noise level is so high at the lower frequencies, but within that
limitation they are effective and probably billions are in daily
use inside people's radios.

73

Alan

-----Original Message-----
From: nec-list-bounces+alan.boswell=baesystems.com_at_robomod.net
[mailto:nec-list-bounces+alan.boswell=baesystems.com_at_robomod.net]On
Behalf Of D. B. Miron
Sent: 05 July 2005 16:30
To: nec-list_at_robomod.net
Subject: NEC-LIST: Loopstick data?

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Good day,

Does anyone have experimental data on a single-layer coil
antenna loaded with a ferrite rod? I want to try out some
parameter prediction calculations. Data for the coil with
and without the core would be very helpful.

Regards,
Doug Miron

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