LF: Re: Ferrite wideband antennas?

[pws <pws@legal-medicine.de>]

Hi again Daniele,

I forgot some words about shielding.

Do not use solid sheet. I just built a small receiver for rtty at 147 kHz 
for weather report reception when sailing. Using a fine looking u-shaped 
copper shield the signal went down of some 10 dB even if spaced 4 cm apart 
from the rod. And it did not improve the SNR considerably.
Using an envelope from old SCSI flatline soldered together only at one side 
the SNR went up of >10 dB inside the house. The effect is incredible. My 
guess is that Eddy currents are responsible for this. So if possible shield 
your ferrite antenna coil by a "feathered", comb-like structure with 
multiple conductors running in parallel around the rod. They may overlap 
some cm if isolated. And in contrast to solid shielding distance doesn't 
matter.
Peter, df3lp