Jim
Incorporate both systems for max flexibility.
With all this hi tech discussion its hard to believe that no one is
transmitting or receiving at present from the UK, and not that much interest
from EU.
de mal/g3kev
----- Original Message -----
From: "James Moritz" <[email protected]>
To: <[email protected]>
Sent: Tuesday, August 16, 2011 7:17 PM
Subject: LF: Re: ferrite coil
> Dear Mal, LF Group,
>
> >Instead of winding a tight coil on to a ferrite rod to get 270 uH and
> >tuning with a 250 p variable capacitor...
>
> The required tuning capacitance would be about 5000pF.
>
> >...instead wind an air core coil and move the ferrite rod into/out of
coil
> >for the required inductance necessary for frequency >of interest. This
> >would further reduce losses.
>
> You could tune inductance downwards in this way, but unfortunately any
> reduction would be accompanied by reduced magnetic flux due to the
received
> signal in the antenna winding. So the signal amplitude would be reduced.
> Also, I doubt if losses actually would be lower - certainly, the coil
> without the ferrite rod will have a much lower Q than with the rod in
place,
> so a point must come as the rod is withdrawn where Q decreases rapidly.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
>
>
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