At 4 am, I said: " Since each band would have a
filter in the output, harmonic output could easily be greater than from the
Pi-L."
That should have been "harmonic output should easily be less than from a
Pi-L"
This is an example of what happens when the computer runs without sufficient
rest.
Colin K7FM
----- Original Message -----
From: "Lamb" <k7fm@teleport.com>
To: "Steve Thompson" <g8gsq@qsl.net>; <amps@contesting.com>
Sent: Tuesday, December 18, 2001 4:55 AM
Subject: Re: [AMPS] Inductors
>
> Various means are available to vary the inductance over a limited range -
> without resorting to a large rotary inductor. How about this for a
> suggestion.
>
> Amplifier is built with small value variable C on the plate side. Then go
> though a bandswitch (or vacuum relay) to a choice of output band circuits.
> Each band is fitted with a fixed capacitor input (except on 10 and 15
> meters, where the small value air variable is sufficient). Then, each
band
> circuit has a separate L (with limited adjustment similar to a variable -L
> link or a spacing change to vary L), then to a fixed output capacitor set
> for 50 ohms. Each band would then have a separate adjustment on the front
> panel for that particular band. The output of the pi-network would then
be
> switched with either a relay or a coupled wafer. Since the pi-network
would
> not have sufficient rejection of harmonics, an additional low pass filter
> for each band segment would be switched in to eliminate harmonics.
>
> This setup would have the advantage of bandswitching with only a slight
> retuning of one capacitor. The inductor would be pretuned to that band
> segment. Parts would be easily home made. Since each band would have a
> filter in the output, harmonic output could easily be greater than from
the
> Pi-L.
>
> One possible problem might be the unused tank circuits. You would not
want
> to pick up enough voltage to blow the fixed capacitors. Shielding could
> solve that problem.
>
> Have not thought it through yet, as it is 4 am and I could not sleep.
> Perhaps a bit more sleep and I will abandon the idea. Perhaps it is
easier
> to spend $5,500 for an autotune amp.
>
> Colin K7FM
>
>
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>
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