Re: Why are some radios so directional?- FARMERIK

Pollock,Raphael E <rpollock@...>

Thank you both for your answers!

From: ultralightdx@... <ultralightdx@...>
To: ultralightdx@... <ultralightdx@...>
Sent: Sun Apr 11 16:01:28 2010
Subject: [ultralightdx] Re: Why are some radios so directional?- FARMERIK


--- In, "ferrite61" <dxrx@...> wrote:
> 1.) This property involves the "Q" or figure of merit of the antenna.

Higher Q does more than improve selectivity. As you've noted, higher Q is associated with lower loss, yielding better signal strengths as well. That's why I tried a variety of toroid diameters, seeking that Holy Grail of higher Q. The limiting factor is probably the Q of the tuning varactor. Crystal-set builders spend big bucks on high-Q tuning capacitors to go with their high-Q coils.

A LW coil wound on a 2.4-inch toroid isn't showing any advantages over one wound on a 1.4-inch toroid, but at 150 kHz I might do better using Litz wire. A dB here and a dB there, and all of a sudden you're hearing stations you couldn't hear before. I'm just finding it impossible to muster the ambition to wind 125 turns (25 feet) of Litz on a toroid!


Jim, KR1S 

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