On Tuesday, May 17, 2011 15:43:27 Joseph Apuzzo wrote:
> As in GPERDICT for locating satellites and say QAntenna for antenna design
> 9600bps modem emulators to send digital information etc.
> Focusing on just satellites and not the whole area of radio communications,
> it can be more focused on how software ( F/OSS ) plays a role in the hobby.
> I think communicating via satellites for around $100-600 is an interesting
> thing to do. ( you can do it with a hand held and a home-made antenna
> http://www.wb5cxc.com/satant.html )
> maybe mention the RIT high altitude balloon
>
> I started working in satellite communications back in 1987 when I worked
> for a small company (DX Communications), which made the down-link
> equipment for cable companies ( as well as some K-Band receivers )
> So I do have some background on this topic.
>
> Sorry are people NOT taking me seriously on this topic?
> Maybe the LUG is not the correct venue for this?
Okay -- some interesting things about satellite communications:
1) you need antennas with high gain
2) antennas with high gain get it by having a narrow beam width
[that's exactly where the gain comes from]
3) narrow beam width means needing to TRACK the satellite
4) tracking means needing to steer the antennas
5) the satellites generally use circular polarization
The combination of these 5 things above means you generally end up with 2 Yagi
antennas, one mounted in a horizontal polarization, one mounted with vertical
polarization, and then fed the same signal 90° apart electronically using a
short piece of coax cable in order to create circular polarization. These are
then mounted to a set of 2 rotators (one per axis) to allow Azimuth and
Elevation steering, then connected to a computer which uses the Keplerian
Elements of the satellite you want to track in order to keep the antennas
pointed at the satellite. The satellites also usually have separate up/down
frequencies, just like repeaters do.
In short, there's quite a bit that goes into this kind of rig. I haven't done
any of this stuff at all -- but my dad has. Even when I was a wee pup way
back when and had a TI-99/4A my dad would use it sometimes with a satellite
tracking program and would print out these long lists of Az/El tables for how
to steer the circularly polarized Yagis in the back yard for various ham
satellites. To me as a kid it was annoying because my computer was unusable
for a few hours -- but at the same time it was fun to see that the computer
could also be an indispensable tool for this work, which would be tedious to
do by hand. My dad seemed to get a kick out of doing the satellite stuff for
a while, then he got into "moon bounce" (which is literally that), then got
into Amateur Radio TV (and I mean "live" TV, not slow-scan TV), and other
stuff. The term "Ham Radio" encompasses a whole lot more than it sounds like.
> On Tue, May 17, 2011 at 2:48 PM, Gary Mort <[email protected]> wrote:
> > Amateur Satellites like Nano Sattelites? I think there is an open source
> > design for a cube sat I ran into a while ago[under 1kg small cube's
> > ]...or amateur such as bouncing signals off existing sats?
> >
> > On Tue, May 17, 2011 at 5:12 AM, Joseph Apuzzo <[email protected]> wrote:
> >> Starting to research on short and long digital communications ( with
> >>
> >> special focus on amateur-satellites )
> >>
> >> D*STAR
> >> http://en.wikipedia.org/wiki/D-STAR
> >>
> >> D-RATS
> >> http://www.d-rats.com/
> >>
> >> There is enough cross-over to ground it in "open source".
Definitely.
> >> But what I would really like is to pair up on this topic with someone
> >> who can help me with the Amateur Radio parts.
I'm game.
> >> The intent would be to give the talk to our group but also to any other
> >> group that would be interested like Maker fokes (Squid wrench) or any
> >> local HAM group.
> >>
> >> So I'm looking for 1) suggestions 2) people I should work with.
> >> Again would not be ready for a talk until Fall at best ( taking my Tec.
> >> test in June then will be able to work hands on etc. )
> >>
> >> Joesph Apuzzo
> >> GNu-Joe
I think I've given you some hints as to what to look into above if you want to
start doing satellite work.
I'm going to try to get my old Packet setup up and running, for starters.
-- Chris
--
Chris Knadle
[email protected]
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