[amsat-bb] Re: satellite average elevation & new birds

[Clayton Coleman]

Just a short time ago after I moved into a new shack, I operated for a
month with an Elk at 15 degrees on a tripod.  Armstrong rotor.  I worked
all the current satellites right up through the first week we had AO-73's
transponder available.

Pay close attention to comments WB4APR has made about setting the fixed
elevation based on the lowest horizon you can work.  For example, if it
takes ten degrees for you to clear a mountain, twenty five degrees is
probably okay.  If you have a clear horizon view, fifteen is probably
okay.  The goal is to have as much gain available at your lowest elevation
to increase your available range.  YMMV

PS A preamp goes a long way in a fixed elevation setup.

73
Clayton
W5PFG
 On Dec 17, 2013 7:24 PM, "Ted" <k7trkradio at charter.net> wrote:

> I'm kind of looking for an update from Bob, but can't find his email right
> now...
>
> But the question is, in view of what appears to be some renewed interest in
> working the new cube sats, et al, is asking Bob to comment on his earlier
> thoughts on using antennae at fixed elevations. For me, I'm using my Elk on
> a Rat Shack rotor at a fixed el per Bob's recommendations. (I'm still
> struggling with PCSAT32...!!!%^&*!!) but, this antenna set up is very cost
> effective and seems to perform pretty well.
>
> For example, Joel Black has asked for some advice in an earlier posting. My
> concern is that new operators or those returning run out and spend a bunch
> of $$$ on a new setup. No one knows how long the current crop will last or
> if a new crop is in the future, so probably some caution on the Visa is
> warranted.
>
> Just asking  (and especially Bob)
>
> 73, Ted
> K7TRK
>
>
> -----Original Message-----
> From: amsat-bb-bounces at AMSAT.Org [mailto:amsat-bb-bounces at AMSAT.Org] On
> Behalf Of Bob Bruninga
> Sent: Tuesday, April 12, 2011 8:23 AM
> To: amsat-bb at AMSAT.Org
> Subject: [amsat-bb] Re: satellite average elevation
>
> > we used a horizontally polarized yagi fixed at 30 degrees above the
> > horizon.  That worked very well..
>
> Thanks for the confirmation.  Yes, elevation rotation is simply not needed
> at all for LEO spacecraft and modest beams.  A mild, fixed tilt modest beam
> is just perfect.
>
> But, the "30 degree" angle myth is very pervasive throughout amsat,
> whereas,
> the optimum angle is more like 15 degrees.
>
> A 30 degree up-tilt gives up too much gain (-3 dB!) on the horizon where
> signals are weakest and where satellites spend most of their time, and puts
> the gain in an area of the sky where the satellite is already 6 dB stronger
> and is rarely there (giving you max beam gain where you need it least).
>
> If you look at the sketches on the web page, the optimum angle is more like
> 15 degrees up-tilt.  It preserves max gain on the horizon within 1 dB
> (where
> it is needed most) and focuses the breadth of its gain on the area of the
> sky where the satellites spend something like 95% of their time.  For the
> missing 5%, the satellite is right on top of you and almost 10 dB stronger
> without any beam at all.  Oh, and the 15 degree up-tilt beam is also
> perfect
> for Terrestrial operations as well.
>
> See the sketch on: http://aprs.org/rotator1.html
>
> In some future life, if we ever get back to HEO's and huge OSCAR arrays,
> then elevation rotors have a place.  These high-gain beams have such narrow
> gain patterns, that higher precision tracking is a must.  (Though it is
> complete overkill for LEO's).
>
> Using these OVERKILL arrays for LEO's adds significant complexity to LEO
> operation requiring higher precision tracking, elevation rotors, better
> timing, fresher element sets and automated operation.
>
> Using a TV rotator and 15 degree fixed tilt beam is much more forgiving...
>
> Bob, Wb4APR
>
>
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>
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