Re: [Amps] High C out

["Phil Clements" <philk5pc@tyler.net>]

> Well, I wasn't for sure as I cant decipher what he wants. He mentioned 
> wanting to know how to increase the inductance by 300 nH, which squeezing  the 
> coil would raise it. In a Pi-L, the load C is in between the two coils  and 
> tune C at the coupling capacitor off the anode. In other words, the  added 
> coil is between load C and the load. Without knowing what he wants  to do for 
> sure, about the only thing I could advise is answer his question  about how to 
> raise inductance by 300 nH. With a circuit description in  detail, what he's 
> wanting to accomplish, and at what frequency, I dont  know what else to tell 
> him.
>
> Will

What he wants is a series L between the tube anode and the tune C to cancel
out enough anode C to keep the tune C from bottoming out at minimum on the
higher bands. This is an old common practice before vacuum variables with lower
minimum C than a "bread-slicer." Even some vacuum jobs do not have single-
digit min. C when fully open. The down-side is that the series coil will be 
there
all the time, and MAY affect tuning on some lower frequency bands. The small
inductor is in addition to the Pi and/or L coils in the tank circuit.

You cannot monkey with the Pi coil, as Q will soar if you don't stay with 
calculated
values for your particular lash-up to keep the tank Q under 15-20 or so on 10/12 
meters.

Clear as mud now??? This is an old trick; been in many handbooks.

(((73)))
Phil, K5PC


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