"Henry" wrote in message
...
Hello group -


My new interest is ferrite rod antennas.

I'm looking for a (possible) interesting doc:
UK magazine Practical Wireless, April 2000, pages 38 and 39 "An
Experimental Ferrite Rod Transmitting Antenna" by Richard Marris G2BZQ

Seems not on the net and the author doesn't have an email address or is
gone.


Would be nice if someone can send it per email.


Anybody interested in ferrite antennas can contact me for info sharing.


Best regards -
Henry Kiefer

Henry,

I vaguely recall reading this article also. As I recall it was claimed that
it was possible to use ferrite quite successfully to receive and transmit on
frequencies up to 7MHz or 40 metres. I believe the antenna used a couple of
six inch ferrite rods side by side with the old medium wave and long wave
windings removed and perhaps 15 or 20 turns of wire to resonate on 40 metres
wound over a sliding card sleeve. The sleeve was made loose enough to slide
along the ferrite rods to achieve the best point of operation.

I would suggest getting a couple of old ferrite rods and experimenting with
some wire and a capacitor for resonance.

The problem with ferrite is that it tends to be very lossy in transmitting
applications. The principles that concentrate received signals in a loop of
wire wound around the ferrite rod, result in transmitted signals becoming
concentrated in the ferrite rod, which then absorbs a lot of the RF energy
and reradiates it as heat. One or two six inch ferrite rods should be okay
for transmitter powers up to 10 watts.

The reason for using ferrite rods was to develop a small antenna with
similar properties to a dipole. One that could be rotated in the shack to
null out interference etc. Transmission efficiency will be very poor, but
the directional properties and the fact that you only need to radiate
milliwatts to work thousands of miles using CW may mean this type of antenna
will work fine for you.

One thing it wasn't, was a type of miracle whip. I have built one of those
following instructions on the web and it works okay at QRP powers from 3.5
MHz to 28 MHz. The transmission efficiency is rubbish, but it gets some sort
of a signal out and is fine for receiving. The miracle whip type of antenna
uses a wire wound ferrite toroid as a matching autotransformer to match the
impedence of a short whip to 50 ohms.

Try the link below for some more info on how ferrite works for receiving and
transmitting antennas

http://www.st-andrews.ac.uk/~jcgl/Sc...rt7/page5.html

This page suggests transmitter powers of less than a watt be used with
ferrite, but I think it depends on the heating effects you get with the rods
you end up using. There are many different formulations used in making
ferrite rods and toroids and some rods will work very much better than
others in this type of application.

Mike G0ULI