dansawyeror wrote in news:gdKdnbMJd42f-
:

All,

I am interested in experimenting with ferrite core receive antennas. I
have about a dozen .4 by 10 inch rods. The primary band of interest is
75m. My question is:

1. For best reception is it better to make a fat or a long antenna? I
cannot find much written about these antennas and have not found any
equations.


I seem to recall that this is a design problem often treated in texts.
Certainly Kraus has a treatment in his book.

In the Fig 3 in my article
http://www.vk1od.net/SmallUntunedSquareLoop/index.htm , I give the
formulas for calculation of the o/c voltage in a single turn loop in air.
In the case of a ferrite loop, the area will be the csa of the loopstick,
and you will have to multiply the single turn value by the number of
turns and include the effect of relative permeability of the ferrite. You
can then proceed to work out the source impedance for the ferrite coil
and the loaded voltage (including the effects of tuning if used).

The literature states the efficiency of these antennas can range from a
10**3 to 10**6 a dipole of the same size. Let's not argue the high end
but accept the low end for discussion. Does this ratio refer to length
or diameter?

Is efficiency a good indicator of the "goodness" of a rx antenna where
the ambient noise is high (as it is on 80m)?

Perhaps if you want to receive normal signals, you just need an antenna
that will deliver 6dB more noise (ie from ambient noise) to the receiver
than its equivalent internal noise. In that case, the received S/N will
not be more than 1dB worse than with a lossless antenna system.

Owen