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[AMPS] More Input Tuned Circuits with Powdered Iron Toroids

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Subject: [AMPS] More Input Tuned Circuits with Powdered Iron Toroids
From: (Frank Donovan W3LPL)
Date: Wed, 10 Feb 1999 22:09:42 -0500
Several readers asked that I provide an update to
my 3-1000Z pi-network input tuned circuit chart after
I had completed the replacement of the National XR-50
slug tuned coil with a powdered iron core in my 160M
monoband amplifier.  It took less than an hour to complete
the replacement this evening.  The complete table of 160-10
meter pi-network component values follows this text.

As a reminder, count the "turns" in any toroidal inductor
by counting the number of times that the wire passes thru
the center of the core.  Yes, this results in a turns count
exactly one turn greater than you might count intuitively.

Input tuned circuit configuration notes:

A 0.02 uF mica blocking capacitor is connected directly in
series between the exciter and the input of the pi-network.

C(in) is the pi-network capacitor on the exciter side of
the pi-network.  It is grounded to exactly the same ground lug
as C(out).

C(out) is the pi-network capacitor on the 3-1000Z side
of the pi-network.  This capacitor is connected directly from
the filament pin to a ground lug on the chassis immediately
adjacent to the 3-1000Z filament pin.

An additional 0.02 uF mica capacitor is connected between 
the filament pins to keep them at the same RF potential.

Final input tuned circuit pi-network values:

Band   C  (in)   Powdered Iron Toroid                       C (out)
160      3700    25 turns #22 on a T68-2  (red)         3000
  80      1820    17 turns #22 on a T68-2  (red)         1500
  40        910    14 turns #22 on a T50-6  (yellow)       750 
  20        470    10 turns #18 on a T50-10 (black)       360
  15        300      8 turns #18 on a T50-10 (black)       240
  10        240      6 turns #18 on a T50-10 (black)       180


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