To: | "[email protected]" <[email protected]> |
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Subject: | Re: LF: Re: Ferrite wideband antennas? |
From: | Daniele Tincani <[email protected]> |
Date: | Wed, 31 Aug 2011 05:01:40 -0700 (PDT) |
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Hi Peter, LF,
is a specific type of wire recommended (or not recommended) for the coil?
Best regards
Daniele
From: pws <[email protected]> To: [email protected] Sent: Tuesday, August 30, 2011 5:17 PM Subject: LF: Re: Ferrite wideband antennas? 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 |
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