On Fri, 6 Oct 2006 17:24:40 +0200, "Henry Kiefer"
wrote:

You can use ferrit antenna rods. That works for receivers very fine in VLF
band and for transmitters too - as long as the ferrit won't go into
saturation.
That is a magnetic antenna and it is much shorter than the equivalent
mentioned.

Ferrite rod antennas with perhaps -50 to -60 dB gain are useful since
the extremely high band noise at VLF. It does not matter very much if
both the wanted signal and the band noise is attenuated by 60 dB, as
long as the wanted signal at the antenna terminals is stronger than
the preamplifier thermal noise.

For transmitting, such antenna would be ridiculous.

In order to get 1 W EiRP as allowed on the 135 kHz amateur band in
many countries, you would have to feed 1 MW into an antenna with -60
dB gain. The ferrite rod would saturate at much lower power levels
such as 1 W or a few mW. Most likely you might get a few nW radiated
power without saturating the rod.

Paul OH3LWR