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Re: An V/U antenna for LEOs?



Hi Bob... and Michael...

Interesting comments about omni antennas.  My observations related to UO-14
have been very similar.  First, I've done most of my operating with a 19 in.
dual band flexible whip, and had the best luck in the middle of the pass.
The bird is essentially full quieting and one or two divisions on the HT
S-meter for a few minutes, particularly on near overhead passes (Say 50
degrees of more, especially at 75 degrees or more) but very marginal at the
edges.  For example, I heard TI5JD near the end of this morning's pass, but
the satellite was weak, and I couldn't hear myself, even between the
alligators.

I tried UO-14 with my FT-2700RH set up at my parents' place where I have an
omni 6 dB gain collinear on the roof at about 30 feet, and  have been unable
to hear it.  The most likely culprit seems to be old coax with too much
loss, though cable TV leakage causing desense is a possibility, too.  I can
hear my own signal through RS-13, and have heard SO-35 on the same antenna,
so the 2 meter sides seems side seems ok.

I've also worked SO-35 (Parrot and Mode J) with a 3 db gain collinear inside
my own apartment with a very short coax run.  I've tried UO-14 inside the
apartment with a bunch of different antennas, but no go.  The signal seems
to be covered up by a carrier, presumably from the cable-TV system.  I have
to walk well away from the building to hear the bird on my HT.

Hope this helps!
Frank
wb2bxo@AMSAT.Org

----- Original Message -----
From: Bob Bruninga <bruninga@nadn.navy.mil>
To: Miguel A. Vallejo <ea4eoz@jazzfree.com>
Cc: <amsat-bb@AMSAT.Org>; <shr@dei.inf.uc3m.es>
Sent: Saturday, October 14, 2000 8:28 PM
Subject: Re: [amsat-bb] An V/U antenna for LEOs?


> On Sun, 15 Oct 2000, Miguel A. Vallejo wrote:
>
> > After almost 8 years since my last contact via satellite, I'm trying to
> > back again to this world. I've been listening with a walkie and rubber
> > duckie antenna some UO-14 and UO-11 pases and surprisingly, the signal
> > was really great!.
>
> Yes, Mobile or HT satelite operation gets rid of COAX LOSS.  That is why
> it worsk far better than a HOME station.  Also siec an HT or a CAR  ROOF
> can see exactly the same sky as an antenna 75 feet up, there is no reason
> for any coax.
>
> But no matter how you cut it, the Satellie signal will be 6 to 10 dB
> further away at low elevation angles.  Thus you get a good signal for the
> center few minutes of the pass but  must have a gain antenna to see any
> more.
>
> > > Now I look for an aerial, that permits me to work these LEOs (SO-35,
> > UO-14, FO-20, FO-29, etc) with a 50 watts dual band multimode rig... I
> > tried to test a egg-beater antenna, but I'm unable to find the RG-62
> > cable... Will a low gain vertical do the job? O:-)
>
> No.  You need gain.  Try the 19.75" 2m whip over a ground plane.  It has
> almost 8 dBi of gain at the 435 MHz downlink abouve about 30 deg.  Thus it
> works best when the satllite is also at its closed point.  It wont hear
> anything below about 20 deg tho, nor will any other simple omni.  The
> satellites is 6 to 10 dB further away, and nothing but a beam will pull it
> out..
>
> de WB4APR
>
> > How do you work these sats? Please, feel free to write at my own address
> > with your antena set-up and the performance you got with it... I need
> > some ideas!
> >
> > Thanks in advance!
> >
> > /-------------------------\
> > |    Miguel A. Vallejo    |
> > |   ea4eoz@jazzfree.com   |
> > \-------------------------/
> >
> > ----
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> >
>
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>
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