[amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE

Alan VE4YZ ve4yz at mts.net
Fri Sep 25 20:44:55 PDT 2009

I rarely use my Arrow and 2 dual band HTs, but, dragged them out this week
because I'm scheduled to do a high school demo in 2 weeks and thought I
better start practicing my technique again, update the KEPS in my Palm
PocketSat+ and get the battery packs charged.

So this discussion in the last couple of days is very relevant to me and
here's my 2 cents...

The only compliant I have about the Arrow is that it looses it's speckles
and the plastic tips fad to white when used outdoor for long periods :-)
Several years ago I ran it for a full year on the roof with a hygain TV
rotator and fixed EL of about 30 degrees. The arrows are now plain

First I view all anecdotal comparisons of before and after results with some
caution.  A diplexer change from the OEM to another cannot account for the
improvement in one pass with fades to the next pass with no fades IHMO.  It
is so, please tell me the science behind this.  If a defective diplexer was
acting as an attenuator then I sure can see there would be an improvement in
signal.  In my location, 2 low passes with the same max elevation on the
same satellite can be quite different depending on which part of the horizon
is below the pass - open prairie vs the noise floor of city. Sometimes there
are fades and sometimes there aren't any.  Satellites tumble.  Sometimes to
your advantage and some times they work against you.

Now, as to the Arrow OEM diplexer; with the 2 HT's I don't use it except as
a mode J filter, see

http://www.amsat.org/amsat-new/articles/Mode-J/ to reduce desense, and, a
mini UHF preamp

http://www.hsmicrowave.com/html/amateur_lna.htm , and, anecdotally I can
tell you that I can see the increase in bars on S-PO Meter and these old
ears can hear the difference when the preamp is switched on and off. 

For those of you who want to use an external diplexer such as a Comet, you
can still use the OEM diplexer at the same time as a filter.

BTW yesterday I just practiced listening and heard a monstrous booming
signal from ISS, got to hear 4 or 5 answers to questions during the Ottawa
ARISS with the Arrow and a max 10 degrees pass, no preamp needed,  LOS just
under 5 degrees.  Also AO-27 max 20 degrees over Eastern NOAM until it went
digital - ever notice it goes digital just as it hits the 49th parallel? Is
that an anti-Canadian thing?

73, Alan VE4YZ
AMSAT LM 2352 



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