RadioBanter - View Single Post - How to match 190 +j140 to a 50 ohm source?

Richard Clark · December 8th 07, 08:42 PM posted to rec.radio.amateur.antenna

On Sat, 8 Dec 2007 12:01:50 -0800 (PST), wrote:

I'm worried about the real part, its just that after the reactive part
is nice, I don't think matching the real part will be hard.

That is a comforting illusion, but only an illusion. If you are
versed with the Smith Chart (another archaic tool from the student's
perspective, but immensely used by the practitioner), then you would
appreciate this.

If this course is more than a side-bar to your studies (or if you are
progressing into RF or Linear design), then the Smith Chart is your
best friend.

I've just been reading on the internet and stuff about gamma matches
and at least one of them has said that gamma matches only match the
reactive part. from what you say I guess this is not true?

Only partially. You need to read it again to see if that reference
was in fact focusing on removing reactance (it does, as that is one
purpose) while soft pedaling resistance (which for the example may
have been sufficient).

Hopefully I can get up to school later and read some real material,
but for right now the internet is all i have.

It should do quite well.

We weren't given a concrete design. More like make a helical antenna
with 12db forward gain at 450 MHz--that's it.

The Helical antenna was invented by a Ham, who is also one of the most
respected professors of RF and antenna engineering, John Kraus, W8JK.
Google
kraus helix antenna
One of his students, also a professor in RF and antenna engineering,
J.C. "Mac" Mc Laughlin, N8TT, contributes to this group as well. (You
would do well to check your school's teaching directory.)

You are probably close enough, within an hour's drive, to knock on his
door at the University.

I'm about 99% sure that we set up the analyzer correctly. We tested
some dummy loads (like opens, shorts, etc) on end of the feedline and
they showed up as expected on the smith chart.

That should be sufficient.

Finally, I kid you not. Nothing about impedance matching in this
class. I know a little about L networks and the like, but I don't
know how to implement these networks at high frequenices.

It's just at a smaller scale. A stereo microscope can be an useful
aid. The trombone lines are not that problematic either and could
merit extra credit if your scores are a bit shy.

73's
Richard Clark, KB7QHC