I based mine on the Eimac design which morphed into the W6PO. I used
flappers and aluminum discs for tuning on 4CX250/8122 copper tubing amps in
the past for 2M and never had perfect tuning stability. With the vacuum
variable (which adds its own minimum C that shortens the lines) there are no
hot spots or tuning drift which is hard to attain with some other designs.
The upper part anode chamber fits a 17" wide chassis with lots of room at
the rear for a 30A fil xfmr, bias supply. Nothing is cramped and could
easily be a table top amp of less width. I elected for rack mounting which
has other bands and a common PS for the amps.
Carl
KM1H
----- Original Message -----
From: "jeff millar" <jeff@wa1hco.net>
To: "Roger" <sub1@rogerhalstead.com>
Cc: <amps@contesting.com>
Sent: Monday, November 16, 2009 1:55 AM
Subject: Re: [Amps] Stripline design
> 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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