[AMPS] Roller Inductors vs. Bandswitches ... which is best?

measures 2@vc.net
Tue, 6 Feb 2001 16:08:44 -0800

>I have just about collected all the parts to build my next project and I
>will soon be faced with the decision of how to switch bands with the final
>tank circuit. I see three options:
>1. Use the EF Johnson 222-101 variable inductor that I've been saving for
>the last few years.

The 222 is good for 15 out.  

> I used a roller in my last large amp, chiefly do to the
>fact that I had it and it saved all the trouble of fiddling with taps and
>2. Use a big strap wound inductor and large ceramic switch. I have the coil,
>but will need to locate a switch.
>3. Use the aforementioned coil but switch it with relays, which I would
>still need to procure. This offers the advantage of being able to remote
>control the band change at some point in the future.
>I am hoping some of the more experienced builders can offer some opinions
>and suggestions regarding the technical merits or shortcomings of these
>three choices. Is one method or the other more subject to random parasitic

No.  Parasitic resonance exists before one gets to the tank inductor. 

cheers, Theo

-  Rich..., 805.386.3734, www.vcnet.com/measures.  

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