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Re: [Amps] Stripline design

To: Roger <sub1@rogerhalstead.com>
Subject: Re: [Amps] Stripline design
From: jeff millar <jeff@wa1hco.net>
Date: Mon, 16 Nov 2009 01:55:56 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Roger...

The best place for design examples of 2 meter amplifiers is
http://www.nd2x.net/base-1.html
It's aimed at amps using the Russian tubes but the designs work with any 
tube having a similar size and plate capacitance.

My personal favorite is the PA3CSG half wave line approach because it 
uses very few specialized components and doesn't run high circulating 
current through any capacitors or joints in metal pieces, but it does 
result in a physically large amplifier.
http://www.nd2x.net/PA3CSG-2.html

Assuming you use capacitive flappers for tuning power output coupling, 
it's very easy to design a stripline by cut and try. The strip line is 
designed to be physically large with a lot of surface area for current 
carrying. Some people talk about making it be a certain impedance, but 
that's totally not a factor. Wide lines have lower inductance and have 
to be longer, that's all. To set the line length, uses an impedance 
bridge on the output port, or couple a grid dipper into the cavity with 
the cover mostly on and adjust length with tune and load flappers at mid 
range.

The W6PO design uses two quarter wave lines on each side, presumably to 
balance currents, but that doesn't seem necessary on 2M.

jeff, wa1hco

Roger wrote:
> I'm looking at building a 2-meter amp using a stripline with a pair of 
> 3-CX800's or 4CX-800's, but I've not found any real data on the design 
> (dimensions) of the actual strip line.  Another possibility is building 
> the 6 'n 2 amp in the ARRL classic amp design handbook. I also have a 
> Henry 2002A using a single 3CX-800 with a strip line.
>
> Unlike using the tube characteristics and designing a standard Pi or 
> Pi-L network for a given Q, I've found no information on strip lines in 
> any of the hand books.  Yes, there were a couple of amps using one and 
> the dimensions were given, but if the design information was there I 
> missed it.
>
> The only thing I found on the net were the download sites that appear 
> free until you give them your information and then they want you to 
> pay.  I'd probably sign up if they told me the charges up front. 
>
> 73
>
> Roger (K8RI

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