[amsat-bb] Fixed elevation - how many elements?
hbasri.schiers6 at gmail.com
Mon Jun 17 12:31:43 UTC 2019
10 dBi gain antennas have enough 3 dB beamwidth that you can fixed EL at 15
deg, and still have good horizon gain (where it is most needed), and only
see loss directly overhead for a 20 or 30 sec period (Might even be
shorter). See Bob Bruninga's posting about how this works, it is VERY
informative. Applies only to LEO birds.
I am about to use an EAntenna with 5 el on 2m, 8 el on 70cm, with specified
gain of 10 dBi
On Sun, Jun 16, 2019 at 12:19 PM Kenneth P Alexander via AMSAT-BB <
amsat-bb at amsat.org> wrote:
> Hi Martin,
> I think you've analyzed your situation pretty well when it comes to numbers
> of elements, beamwidths, etc. A few thoughts:
> - if you can try a few satellite passes from around your property with a
> handheld yagi, like an Arrow just gain a little first hand experience to
> see what your minimum elevations are going to look like.
> - you might be surprised to find that some houses are more "transparent"
> to VHF/UHF signals than others. There are several ops here who regularly
> work satellites with portable antennas from inside their houses. Don't
> consider every obstacle to be impenetrable.
> With all that said, if I was in your position I'd go for a 3 or 4-element
> 2m yagi and I'd go to the extra trouble of getting crossed yagis so you can
> use circular polarization to reduce signal fading. For 70 cm the
> 7-elements on my Arrow handheld antenna has always been sufficient, and go
> for crossed yagis again. If you think the trees will really be a problem
> then go with 4 elements on 2m and a few extra on 70 cm, but realize that if
> you're buying commercial antennas you're stuck with what the sellers
> offer. This is about as much as I'd want to swing around with an
> inexpensive azimuth rotator (You didn't say what kind of rotator it was)
> Finally, my antenna situation at home was even more awful than yours. My
> back yard was smaller than my living room and it was surrounded by 3-storey
> townhouses on all sides. I decided to become a rover and it was the most
> adventure-packed 2 years of my life! I travelled all over eastern VE3 and
> western VE2 and activated just over 70 grids, many of which had never been
> activated before. Amsat ops are always looking for new activations and are
> very grateful to thos who have the chance to get out there and activate
> I hope this helps a little. You'll get plenty more replies and have lots
> to sort through soon!
> Ken Alexander (VE3HLS)
> So Phisai, Thailand
> Blog: bueng-ken.com
> On Sun, Jun 16, 2019 at 2:44 PM Martin Cooper via AMSAT-BB <
> amsat-bb at amsat.org> wrote:
> > I'm contemplating building a couple of yagis, possibly even crossed
> > ones, and putting them up at fixed elevation (i.e. az-only rotator).
> > What I'm unclear about is how many elements to consider.
> > My location is really pretty dreadful for seeing sky. There's a big
> > hill to the NE that restricts me to above 40 degrees in that
> > direction. I'm in a single-storey house, with neighbouring two-storey
> > houses to the NW, SW, and S. In between all that, there are other
> > single-storey houses, and trees in most of the gaps between houses. I
> > can't afford to put up a tower (and it could never get above the hill
> > anyway), so I'm looking at not too much above my roofline.
> > To at least get through the trees, I'd think more elements would be
> > better. But more elements narrows the beam, and at fixed elevation,
> > that, at some point, will restrict even further how much of the sky I
> > can play with.
> > I'm looking for thoughts on how many elements would be recommended,
> > and how many would be too many, for a fixed elevation, both for VHF
> > and UHF. Ultimately, I'd like to be able to get on the linears, so not
> > limited to the FM sats. Any thoughts would be much appreciated.
> > Thanks in advance.
> > Martin.
> > KD6YAM
> > _______________________________________________
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> > expressed
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