Yes, I am choking over Bob's comments.
Metal work looks good.
It looks like your green clip lead is the output, and the red lead is for the
1.8K termination. Getting this stuff in close and tight is necessary for 10m,
but it's probably ok for under 40m.
I don't see so much of an issue with your layout. It won't impact getting a
resonance on 40m.
You mentioned tank values that seem a bit different than what I find for a 80m
pi-net. I get for a Qo = 12, the input shunt cap is 250 pf, series L =Â8.2
uH, and output shunt capÂ1240 pF. You mentioned you're getting 7 uH for the
coil in the 80m postion. That might be too light. Look for a resonance
higher, around 4 MHz. Perhaps you can preset components with the L/C meter,
re-connect and re-test.
Steve
----- Original Message -----
From: "Robert Bonner" <rbonner@qro.com>
To: "Chuck Curran" <ccurran@wi.rr.com>, "STEVEN & NANCY FRAASCH"
<sjfraasch@embarqmail.com>, "Tom W8JI" <w8ji@w8ji.com>
Sent: Tuesday, July 17, 2007 9:29:07 PM (GMT-0600) America/Chicago
Subject: RE: [Amps] Grid Dipping the Pi network in a new amp?
Hello Chuck,
I looked over your photos.
Hereâs what I would have done different. I can hear Steve choking on his
gum.
The coil would have been in place of where the caps are. You want to keep the
strap to the coil as short as possible and have the UNIT providing all the
coilâ However, Inductance is inductance. My 77DD amplifiers used roller
inductors and the ten meter tap was only  of a turn. It doesnât take much
coil when you are strapping things together.
The caps are then strapped off the coil. The lead inductance to them is
neutralized with the caps.
Iâd get a flange for the tuning cap and get it grounded. Definitely strap
it to ground solidly. J
You can turn the coil on top of the 852 around and have it hook to the back of
the cap instead of using a massive strap over to the other side of the coil.Â
You might want to mount the 852 back somemore from the front to line up the
coil better.
Metal work looks nice.
BOB DD
From: Chuck Curran [mailto:ccurran@wi.rr.com]
Sent: Tuesday, July 17, 2007 8:10 PM
To: 'STEVEN & NANCY FRAASCH'; 'Robert Bonner'; 'Tom W8JI'
Subject: Re: [Amps] Grid Dipping the Pi network in a new amp?
Gentlemen:
I have attached a group of pictures of the amp construction. ÂI will make a
posting on the amps list server ASAP, I just wanted to provide some visual
information too.
Thanks for all of your comments!
Chuck WA9POU
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