> -----Original Message-----
> From: Tom W8JI [mailto:w8ji@w8ji.com]
> Sent: Monday, March 26, 2007 8:21 PM
> To: garyschafer@comcast.net; amps@contesting.com
> Subject: Re: [Amps] TMC amp toroid tank
>
> > Anyone have any experience with toroid tank coils? Is
> > efficiency normally
> > poor on the higher bands?
>
> I'd never use a torrid in a wide frequency range tank
> circuit. If the toroid behaved perfectly as in theory it
> would not work at all over wide frequency ranges.
> This is because in a normal pick up and hold tank switching
> system, without significant flux leakage in the toroid the Q
> would go to zero along with the inductance on higher bands.
> The only way around that problem is to not short unused
> turns, and then you would get into a switch arcing problem
> on higher bands!
>
> In practice most lower mu physically large toroids will
> barely have enough flux leakage to work in circuits
> requiring low Q when turns are shorted. I suspect that is
> the reason for your low efficiency.
>
> 73 Tom
>
Hi Tom,
I could see really killing it if the turns were shorted but this amp uses
taps on the toroid coil it does not short the turns.
The core is about 2 1/2 inches in diameter and about 3 inches in length. It
is wound with what looks to be about #12 wire.
There are also switched padding capacitors on the plate tune and load side.
Also 200 pf of fixed capacitor is switched in series with the plate tune
capacitor above 5 MHz band. Lots of wires running around to the switch.
Plate leads are pretty long.
This is as comes from the factory. Maybe it never worked very well from the
start. Very nicely built.
73
Gary K4FMX
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