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Horizon LEO Link Summary



Thanks to all who replied. Here's a summary of the 6 answers I got to my
working LEO's on the horizon question: [My comments in brackets.]

...RHCP, ...Texas Potato Masher II..., I regularly used to work SO-35 with
0.5W uplink into that antenna, [SunSat had a VERY sensitive rcvr!] and can
easily hear the FO beacons horizon to horizon. [Hearing beacons is one
thing, working the sats is another, as I'm sure Tony knows all too well.]
Tony Langdon

I`m using Tail Twist Loopyagi`s, linear antenna`s which can work in ANY
polarization without any loss or difference in gain or pattern!!! [Sadly
the URL to the actual pictures and construction data doesn't work yet...
www.loopyagi.da.ru links to the Dutch site.] Chris PA5RWE

In my opinion of the last 2 or 3 years of handheld beam operation where you
can instantly "feel" the polarization, that vertical is definately the way
to go. The few times there is enough faraday rotation to make it perfectly
horizontal is so rare as to not be worth it. For the same reason, going
circular would be wasting 3 dB all the time for the 5% of the time when it
might be beneficial. Thus its normally worse than the vertical... [He makes
then, he works them, AND he seems to make lots of mistakes AND learns from
them too! I pay attention...] Bob, WB4APR

[And Tony's reply to Bob] I've always found it necessary to make a few
adjustments, but from memory, vertical isn't too bad.  However, you do get
deep fades on UHF downlinks, and I'd be more comfortable with circular
polarisation for antennas which are fixed. Tony Langdon

When it's down real low, I use my  "SSB" antennas up on the tower instead
of the  "Satellite" antennas  which are on a short tower with  az-el
rotors. It works out pretty good with horizontal polarization only. I have
a  24 element beam on 432 and 12 element  KLM beam on 2 meters, up about 50
feet. [But 5 watts though that length of coax would produce a trickle of
ERP. Plus the need for preamps on the downlink.] Have made lots of QSO's
that way, though. I guess my best DX was  J6 - St. Lucia  a little over
4000 miles to the east on FO-29 and HC8N to the south, about 3300 miles on
UO-14. I had an "almost" QSO with GD4BEG on RS-15 once, we heard each
other, but no QSO. John, K6YK [And I'll bet that John is one of those that
works AO-10 and 40 like a telephone ;-)

Go for RHCP; The only thing you'll lose out on is that, at low elevation
(say below
10 degrees [Which is what I want Rich]), signals get scintillated to the
opposite sense so an RHCP signal would get turned round ... but its not
usually by a complete turn. But a TPM has no gain - use a beam. Richard W L
Limebear G3RWL

>From all this, (for ON-THE-HORIZON LEO work) I get: use a vertical
polarized 2 meter beam, save 3 db (my original thought) and accept the rare
times when the sat rcv antenna goes absolutely horizontal. Given the
Russian 5 watt limit on VHF and up this seems the way to go for transmit.
(And keep the coax SHORT!) Given the often weak signals from the sats with
435 downlink and with potential fading, IF one was using a state of the art
preamp/convertor or hot rcvr on 435, a switchable circular polarized beam
would probably be an improvement over a vertical beam - at 435 it's smaller
anyway! And THEN: maybe have detachable additional director "arrays" and go
for AO-10 and then add a dish and electronics for AO-40! Seems to be a clue
to getting starting with Amateur sats here!

My potential shack is a second story location with tenna's on the flat
(non-metal) roof. All other nearby buildings are single story and there are
NO trees in any direction for all least a kilometer! (Another reason to
keep the windload down!) The horizon is blocked by mountains in a few
directions up to 2.5 degrees.

Thanks to all. Too bad there is NO window of possibility to work any of you
on the LEO's, except maybe the PA. Maybe AO-10 and 40 in the future!

Thx agn, 73, and cheers from finally white Siberia, O.J. Lougheed, Irktusk

Original message:

>Where I am, I not particularly interested in overhead LEO's... nothing
>under them except Siberia! Bob and others point out all one needs is a
>small beam with 10-15 degrees elevation. But has anyone done a "study" of
>which (if any) linear polarization (horz., vert., or 45) is the best
>compromize "on-the-horizon?" This would be useful because with the legal 5
>watts max at UHF in Russia, a longer beam will be necessary. Or at this
>point is it wise to go with circular (which) polarization?
>
>73 - OJ ex-N5JXU, Irktusk


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