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Re: [Amps] Grid Dipping the Pi network in a new amp?

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Subject: Re: [Amps] Grid Dipping the Pi network in a new amp?
From: "Chuck Curran" <>
Date: Sun, 15 Jul 2007 17:41:17 -0500
List-post: <>
Hello to All, and Thanks!


I have received a number of responses, both public and private and all are
helping !  


Here is the current situation:  I have verified the tank coil inductance,
using a CHY 24 LHR meter and also a General Radio 1656 Impedance Bridge.
CHY states 6.9 uH, while GR indicates 7.1 uH - B& W states 7.0 so I feel OK.
This is for 80 meters.


I have an original B&W 852 tank coil brochure, to verify these inductance
claims.  Actually, it is for dozens of B&W items - if you want a scanned
copy, just let me know and I will do it.


I placed a 56 ohm resistor on the output, and a 1800 ohm resistor on the
tube side of the pi-network - nothing changed.  I re-read the e-mails, and I
had used 12" ( 30.5 cm ) leads for both resistors - not good.  On Monday, I
will do it with very short leads.  Tonight I have to grill !


I first used an ancient Heath GD-1A grid Dip Oscillator, circa 1956 or so,
and then  I tried a really new unit from 1964!  An Allied Knight-Kit G-30 -
neither could detect a dip.  I had replaced the filter caps in both, they
seemed OK when checking signal output on a R-390A.


I am placing the grid dip meter pick up coil above the tank coil of the
linear tank coil, with the axis parallel and the coil about .5 inches above
the top edge of the 80 meter section of the coil - lots of pictures are


Anyone willing to grid dip their tank circuit, and report on the results -









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