[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Antenna feed tweeking results



Hi folks,

Well, I spent the day tweeking my helix in a can feed for AO-40's
downlink.  Pictures are on my hamsite:
http://www.jps.net/gregd/hamsite.htm

The changes include:

- new can and cleaner holes in back for the connector and supporting
dowel.  The last one was a little mangled.  The new can is about 1/4
inch deeper, because that's where a convenient ring was to guide the
saw.

- soldered the "bump" of the N connector to the can for better ground

- replaced the 1/2 turn copper strip with a 1/4 turn like it was
supposed to be.

- bent the strip downwards to compensate for the "bump" distance
(thanks Domenico!).

- shortened the helix to 3 turns from 3 1/2, to try for more of the
grill.

- verified the grill's focus was correct, using the sun.  It was.

I've been trying the current pass out, just to see how it behaves.
Checked periodically from MA 17 to 55, and find the signal is similar
to the old feed at apogee last week; NOT what I expected.  Very
uneven signal, at times non-existant.  I might be shooting through a
tree, so this may not be a fair test, but I certainly expected better
signals at low MA than this.  The satellite's pointed sort of this way
at that point in the orbit, isn't it?  (FODTRACK doesn't predict
squint angles, so I don't know what it should be.)

I think at this point I'm going to leave well enough alone, until
the ArcJet burn is over, and the antenna's pointed back down here.

Thanks to all who have helped!

73s,

Greg  KO6TH

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home