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

Richard Clark · December 8th 07, 07:44 PM posted to rec.radio.amateur.antenna

On Sat, 8 Dec 2007 11:22:05 -0800 (PST), wrote:

yep its an end of the semester project. BUT, we never learned anything
about impedance matching, so I feel no shame in asking people like
yourself. Thanks for your help.

The shame is your course approaching the topic to the point of
construction without introducing matching! Only the most trivial
designs escape this necessity.

This, however, may suggest that the particular assigned helix design
was already selected to match, and that your construction, or its
measurement are problematic.

It may be in the measurement given that at this scale (if you in fact
observed scale EXACTLY), it is generally no more complex than
assembling tinker toys.

You may have skipped the step of normalizing your network analyzer
(which I presume you have one, given the resolution of your citation
in the subject line), or you failed to isolate the antenna from the
feed line (aka choking the feedpoint, rather more an archaic term for
students, but well known by those practiced in the art). Both amount
to the same thing.

I'm at home now, and from what I can tell, I can get a good reactive
match by changing the length of the wire from the ground plane to the
connector? (while keeping the wire from the helix to the connector
constant? I think I will try this.

How can you "tell?" The reactive is rarely disassociated from the
real.

The real part I'm not too worried about.

You should, as it is as much a problem as the reactive part.

73's
Richard Clark, KB7QHC