On 01/ 5/12 09:38 PM, Paul Decker wrote:
> Hi David,
> Thanks for the reply and the great information. I can put together some
> specifics and more pictuers of the inside of the deck, and using a copper
> foil wouldbe an easy way to test it. The 3cx800 tube height is taller than
> the 3cx400 so this might play a role. Perhaps the stripline size difference
> in the k1fo's amp is due to the cabinet size, he does use a larger rf chamber
> than what I have.
The case has quite a major effect if it's distance is not much larger than the
spacing between the chassis and the stripline. I'd say if the distance between
teh stripline and the side walls of the case are less than 2-3 times the height
of the stripline, then the walls will have an appreciable effect on the
impedance of the line.
We need to know where the DC voltage is fed, and where the RF
coupling/decoupling capacitors are. Scan the original publications of the
projects.
TXLine is a free program to compute the impedance of transmission lines. It
works with microstrip line, which is your stripline, with Er=1.0. But if the
chassis walls are close, then TXLine will be inaccurate. ATLC could be your
friend, as that takes the presence of the chassis, top panel and the two side
panels, but it's a Unix program, which you may or may not be happy with.
ATLC can't take the end panels into account, as its a 2D simulator, not a 3D
one. A true 3D simulator is difficult to use and expensive.
Another modeling option might be FEKO lite.
If you can send some detailed diagrams, I could be tempted to try to model this
in HFSS
http://www.ansoft.com/products/hf/hfss/
using it's Eignemode solver. I've never used that feature, but I reckon that
might actually be useful.
If I were in your shoes, I'd not worry about the extra length. It will effect
the system, but in a way which you can easily compensate for by changing the
width of the line, so from a practical point of view, it's not a major headache.
The theory is a bit more complex, but I've given you some of it. Depending on
your background, you might prefer to ignore that or research the topic in more
depth.
> Just a quick question, what is a "GDO" you mention near the end of your
> message?
Grid dip oscillator.
http://en.wikipedia.org/wiki/Grid_dip_oscillator
> Get some rest, 73,
> Paul
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