On Tue, 08 Dec 1998 11:12:36 -0600 Douglas johnson <iix@interaccess.com>
writes:
>Bryan, I,m building a stack of vhf amps using a 3cx800a7 tube in each
>and
>am looking for data on a 222mhz plate line for this tube, I have
>articles
>written by K1fo on the 50, 144 and 432 rf decks ,but nothing yet on
>222.
>If you or anybody can help out on this it would be
>great...........Doug,
>W9iix
That should be fairly simple Doug. The tube itself is not that important
so look for any amp using similar tube output capacity, tetrode or
triode. You can dummy up a line with minimal expense and 222 is still a
frequency you can use a GDO to ballpark with.
Another option is to just scale down (sizewise) from a 2M design ...as
compared to up from 432.
The line length is the critical dimension and the width can vary within
reason.
Again, dummy it up with cheap foil and insulators and use the GDO. Save
the Teflon for the real thing if you plan that design. Use an LCR meter
to determine the capacity per square inch of various household materials
for dielectric insulators and pick one that is close to the Teflon/Mylar
you have or plan to use. Dont expect 100% correlation, you still will
have to tweak a bit to compensate for measurement errors, dielectric
losses, etc but it should be darn close.
I like the split line circuit myself with the tube in the center. With a
bit of care and patience you can tap the output right off the line and
eliminate the hassle of a load capacitor. I do that with my 2M 3CX1000A7
and get 1500W out with 80W of drive and 60% efficiency. Sure beats the
mechanical and RF hassles of a flapper capacitor.
Carl KM1H
BTW, I still have 4 of ur sidearms working just fine!
>
>be wrote:
>
>> Looking for a 222 amplifier ready to go. Would like to have
>something
>> in the 400-500 watts or more class. What do you have out there?
>>
>> Bryan W5KFT
>>
>> --
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>
>
>
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>
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