[Amps] Stripline design

[Carl]

----- Original Message ----- 
From: "Roger" <sub1 at rogerhalstead.com>
To: "Carl" <km1h at jeremy.mv.com>
Cc: <amps at contesting.com>
Sent: Sunday, November 15, 2009 11:42 PM
Subject: Re: [Amps] Stripline design


>
>
> Carl wrote:
>> QST and HRM had some theory/construction articles mostly by Eimac 
>> engineers.
>>
>> Ive done some stripline myself but prefer a single 3CX1000A7 and 8877 
>> which I use on 144 and 222.  I remember a dual 4CX1000A article for 2M 
>> that worked well.
>>
>> These days the only 2 x 3CX800 design Im aware of is K1FO's Lunar Link 
>> products.
> That's one of the reasons I'd like to learn a bit of strip line theory as 
> I only have dimensions for a single 3 CX-800 that I could replace with a 
> single 4CX-1500 for legal limit. What I don't know is how going from 800 
> to a 1000 watts pep to the legal limit, or running a pair of tubes might 
> change the dimensions of the strip line. I'd rather not go with the 
> "cut-and-try" approach. Of course there is always the possibility of a 
> single GU-84B/4CX2500, or the GU-73B that take reasonable voltages and 
> currents on the filament, plate, screen, and grid with what appear to be 
> pretty good gain characteristics. OTOH spares might be a bit hard come by 
> in the future.  The GS35 as I understand takes more drive and a step 
> start, but no screen circuit requirements...they're cheap too.
> OTOH I do have a pair of new 4CX-1500s on the way and already have some 
> spare pulls.
>
> The ARRL amp handbook uses a pair of the 3CX-800s in parallel for 6-meters 
> and Push Pull for 2-meters. It appears I could use the 4CX-1500s in that 
> design with little change except for the power supply.  OTOH the dual band 
> controls make the front panel a bit less than elegant in layout.<:-))
> When I finish I want to end up with the legal limit amp(s) on both 6 and 2 
> with no time limit, key down for any mode.
>
> 73
>
> Roger (K8RI)
>>
>> Carl
>> KM1H

Its simply resonant lines, either quarter or half wave modified by the tubes 
output C. Its the length and width that seems to confuse many. That can be 
calculated or cut and try with a GDO.

I use split lines with one side connected to B+ and the anode. It is 
resonated with a small vacuum variable. The other side is attached thru 
several 100pf 5kV doorknobs and grounded at the far end. Rather than fight 
the  mechanical/RF problems of a load cap I simply find a sweet spot near 
the ground end and solder a wire from there to the N connector. Efficiency, 
grid current and tuning stability is exactly as expected and the 3CX1000A7 
has no problem making a lot more than 1500W. Its been running with the same 
used tube for 25 years.

The 222 8877 is set up similar along with the required protection circuitry, 
the 3CX-1000 is near indestructible as its more like a ceramic 3-1000Z grid 
rating with 1500W Pd.

If you look at the Lunar Link pix and schematic you can get a close estimate 
of the line and enclosure dimensions as well as other requirements. Its 
actually pretty simple as Ive seen them on display at VHF/UHF conferences

Carl
KM1H

>> ----- Original Message ----- From: "Roger" <sub1 at rogerhalstead.com>
>> Cc: <amps at contesting.com>
>> Sent: Sunday, November 15, 2009 10:04 PM
>> Subject: [Amps] Stripline design
>>
>>
>>> 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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>>
>>