[Top] [All Lists]

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

Subject: Re: [Amps] Grid Dipping the Pi network in a new amp?
Date: Tue, 17 Jul 2007 23:50:05 -0400 (EDT)
List-post: <>

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. 


----- Original Message ----- 
From: "Robert Bonner" <> 
To: "Chuck Curran" <>, "STEVEN & NANCY FRAASCH" 
<>, "Tom W8JI" <> 
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 

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. 
You might want to mount the 852 back somemore from the front to line up the 
coil better. 

Metal work looks nice. 


From: Chuck Curran [] 
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? 


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
Amps mailing list
<Prev in Thread] Current Thread [Next in Thread>