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Re: LF: Re: Ferrite wideband antennas?

To: "[email protected]" <[email protected]>
Subject: Re: LF: Re: Ferrite wideband antennas?
From: Daniele Tincani <[email protected]>
Date: Tue, 30 Aug 2011 04:54:51 -0700 (PDT)
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Hello Stefan,
 
Thanks a lot for your feedback.
 
Yesterday evening a purchased a bunch of 7 x MU400HH ferrites (10mm x 200mm each) on eBay, planning to join them together "in parallel" to form a fatter rod, no idea if it will be a good choice but let's play with this new toy ;-) Meanwhile I'm collecting ideas and hints from the web about construction (shielding, computing/measuring parameters, ect.). Projects are stacking as usual :-)
 
Best regards
Daniele
 

From: Stefan Schäfer <[email protected]>
To: [email protected]
Sent: Tuesday, August 30, 2011 12:34 PM
Subject: Re: LF: Re: Ferrite wideband antennas?

Hi Daniele,

Could it be possible to tune a ferrite loop over a frequency range as wide as 100-500KHz? Or at least over the EU NDB band (say 300-500KHz)?
Any practical suggestion (and/or references on the web) about how to build it?
I think it is no problem. A narrow band but adjustable antenna is a good choice. Just use a large variable cap, e.g. 2x500 pF. It may be helpful to use switched caps and a smaller variable cap like i did. If you have a high Q antenna, you can then easily fine tune the system.
So maybe 5...100 pF +100 pF+180 pf+270 pF+560 pF or so, depending on your L.
About the ferrites, there are several sellers on eBay who offer a russian MU400HH type. Would it be suitable for LF?
Yes, very suitable. I have exactly these types in my LF ferrite antenna and got a Q of 480. Q will change over the frequency. So maybe it is even helpful to realise a switched L, for the higher frequencies.

73, Stefan


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