Or find someone with Microwave Office and plug in the numbers at let it do
the math. Ive used that program for everything from VHF to millimeter wave
before retiring.
Having AutoCad to assist with the dimensional stuff is a big plus.
Carl
KM1H
----- Original Message -----
From: "Dr. David Kirkby" <david.kirkby@onetel.net>
To: "Roger" <sub1@rogerhalstead.com>
Cc: <amps@contesting.com>
Sent: Thursday, November 19, 2009 6:13 PM
Subject: Re: [Amps] Stripline design
> 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)
>
>
> The theory and the practice do not always agree too much, but some of the
> RSGB
> and ARRL manuals do cover the theory
>
> Basically you need to make a transmission which has an equal and opposite
> reactance to the tube. The reactance of a length l of a transmission line
> of
> impedance Zo is easily calculated - the equations can be found in any
> decent
> book on transmission lines. If you want some references, I can dig you out
> a few
> - I've got several on my book shelves which cover this.
>
> You will need a reasonable understanding of maths to follow the
> derivation, but
> if you only want the result, it is quite simple. It has a coth()
> (hyperbolic
> cotangent) in the formula if memory serves me correct, but a handhold
> calculator
> can compute that.
>
> The impedance of things like coax lines are easily found from theory. For
> non-standard shapes, you might like to look at
>
> http://atlc.sourceforge.net/
>
> which is free and open-source finite difference software. I wrote that
> software
> - there is no need to sign your life away.
>
> It needs a Unix or Linux or Mac OS X system to run on. (That said,
> somebody has
> compiled it to run on a Sony Playstation!) I can't be bothered with
> Windows. At
> the time I wrote it, the software was very expensive in terms of CPU time
> needed, but that will not be an issue now.
>
> I believe the results are very accurate for enclosed air-spaced lines. For
> multiple dielectrics, with open structures, the accuracy drops a bit.
>
> The problem is that while one can do a lot in theory, the practical
> aspects
> means that some things can't be modeled (at least with software I'm aware
> of).
>
> You can't consider a tube to be electrically small at 2m. If you have a
> shoring
> link at the end, you can't consider it has zero length, but neither can
> you
> model its effect accurately.
>
> So basically, while you can do all the theory, in practice it will come
> down to
> cut-n-try.
>
>
>
>
>
>
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