[Amps] Building an Amp 101

Bill Turner dezrat1242 at wildblue.net
Sat Jan 18 13:18:47 EST 2014

ORIGINAL MESSAGE:          (may be snipped)

n 1/18/2014 9:52 AM, Jim Garland wrote:
> I agree that one shouldn't leave the unused segments of of a tank coil
> completely floating, and I don't do that. As you suggest, I connect the
> wiper on the bandswitch to the cold (antenna) end of the inductor so that
> the switch shorts the unused segments. For esample, if operating 10m, the
> 15m tap is shorted by the wiper to the 160m tap at the far end of the coil.


This method works and is commonly used, but there is another way, which 
I think has some advantages.

I have separate coils for each band. They are NOT magnetically coupled 
to each other even though they are in series. Each coil is oriented 90 
degrees to it's neighbor and they alternate vertical and horizontal with 
each band so the coils do not "see" their neighbor.

The tradeoff is this requires larger coils, since even though they are 
in series, they have almost no magnetic coupling between them. The 
advantage is that none of the coils need to be shorted out by the 
bandswitch and therefore no current flows through the "short". I know 
this approach will not appeal everybody but it works for me.

73, Bill W6WRT

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