[Amps] Stripline design

[Paul Decker]

Hi group,

NHY to all!   I am working on an amplifier mod and need some advice.  I have a currently working 70cm stripline amp based on the 3cx400A7 tube.  As everyone knows, that tube is getting rare and expensive.  Since I have a few 3cpx800A7's around here, I thought it might be a good fit to change to that tube, especially for the eme contest at the end of the month.

Besides the obvious physical size and heater voltage, there is a slight difference in cin and cpk, I'm not sure what that will do.  I've never found any design plans, but this stripline is 3.5" x 8.625" long. and the tube is 0.25" (tube center is 1.05" from end) from one end.   

To fit the 3cpx800, I would have to extend the stripline 0.375" so the tube would still be connected making it 9.0" long.  You can see what I mean here:
http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/388232_2684319340428_1029693354_32301613_317232212_n.jpg

Does extending the "null" end of the stripline make any difference?  What effect would this have?

I dug up the K1FO single 3cx800A7 70cm stipline documentation and it shows the stripline as being 3.5 x 9.6875", unfortunately I don't think that will fit in my deck without extra work.  On the other hand though, I looked at K1FO's 2x3cx800 stripline and it is 9.0" long, just like mine would be.  Any speculation on why K1FO single has a much longer stripline than I do and why his two hole has the shorter one?  My guess is the tune flappers might be in different locations and that makes the difference.

Thanks for the insight on this and 73,
Paul, kg7hf