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More 7N1JVW / JF6BCC / K3TZ PatchFeed Testing...



I finally got around to doing a little more on-the-air testing with this 
interesting little patch feed.  Those that have followed my earlier testing 
(and even a contact on AO-40) will remember I was using this patch feed on a 
portable antenna (18" DSS dish). Here are a few pictures of the portable 
setup:
http://home.swbell.net/k5oe/K3TZ_patch/K3TZ_patch.htm

After AO-40 got too hard for me to get into today (although Europeans were 
still easy copy here, many of them 59), I swapped out the helix feed on my 
"main" AO-40 antenna, a 2' BBQ grill with a helix feed.  Here is the antenna 
I have been using since last fall (select "2' Dish Mods"):
http://members.aol.com/k5oe

Using the AO-40 beacon as a test signal and both my TS-2000 and 
HTX-100-feeding-AO-40Rcv as relative signal strength meters, I began the 
testing by first measuring the beacon strength, then swapping out the feed, 
measuring again, and then reversing the operation to double-check the 
baseline.  At almost 60,000 km, and from MA=120 to 150, the QSB was 
significant and constant.  Here is what I observed:

helix feed:  S 0.5 to S 1.0, and 38 dB on AO40Rcv
patch feed:  S 0.5 to S4, and 41 dB on AO40Rcv
patch feed with 1.25" ring:  S 0.0 to S3, and 40 dB on AO40Rcv
helix feed :  S 0.5 to S 1.0, and 37 dB on AO40Rcv

Clearly, the patch was a noticeable improvement over the helix feed, even 
though the "swing" of the QSB seemed worse to listen to it (due to the patch 
being linear?).  Interestingly, I could not copy a single good telem block 
with the patch, but got occasional good ones with the helix feed.  These 
results are very similar to my original observations on the DSS dish.  The 
degradation of the signal from the ring was due, I believe, to it being too 
"deep" and cutting the patch off from the outer portion of the dish:  the 
geometry of the patch is different from a helix and requires a shallower 
"cup" to properly cut off the edge of the dish.  More experimentation 
needed...

The K3TZ page is here:
http://www.qsl.net/k3tz

73,
Jerry, K5OE
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