[URC] Suit Sat

[Alwyn Lloyd]

Awesome.


> The only problem is that Meryki is due in something like 18 hours,
> so there's a slight possiblity i'll be busy.

ooh, well I'm hoping everything works out well on that front :)

> I've got an FM-92 (with a custom ROM so you can set it's VCO directly)
> that works well on 2 meters. I've also got a hand-held scanner that
> will receive FM in the 2m band if anyone wants to borrow it. The
> only other 2M gear I have is a crystal driven rig, and I don't think
> it's going to be easy to get hold of a crystal for 145.990MHz in a
> couple of days.

The handheld scanner should be enough shouldn't it?   Perhaps with a
preamp...

>
> If you're interested, and haven't done any LEO satellite listening
> before, check out www.amsat.org (good for operational information
> on the satelites, and pretty much -the- organisation for amateur
> satellite stuff) and www.heavens-above.com (excellent source of
> pass times for not only ISS and amsats, but also lots of other
> stuff).


Thanks for the links.. something to predict its path will be fairly
useful.

As for the polarisation issue, what about circularly polarised antennas?
aren't they useful for avoinding the changing polarisation issue?
http://home.comcast.net/~ross_anderson/quadix.htm
http://www.amsat.org/amsat/articles/houston-net/antenna.html

according the the articles i have read, they're expecting a 10-15 minute
window for recieveing..   the park at steves or even james oval would be a
good location.

and well, i think recording the whole thing would be a good idea.  there
are 9 different messages... of about 30 seconds duration each.. then a 30
second gap.  so we'd need 10 minutes of contact time to get it all.... :0


Well, i'm keen.  is anyone else??

Alwyn

>
> Stuff you'll probably want to keep in mind:
>
> 	- The polarization[0] of the radio wave 'tumbles' when
> 	passing through the atmosphere, and changes from second
> 	to second. With the wrong polarization/orientation of
> 	your antenna, you can get a loss of something like 20dB[1].
> 	One way of dealing with this is to physically hold your
> 	receiving antenna and (with 2m) wave it around slowly
> 	like a light sabre[2].
>
> 	- Passes for something in a low orbit can be quite fast.
> 	  Normally only a few minutes, with the object moving a
> 	  large distance across the sky. A watch accurate to the
> 	  nearest second, and a laptop with tracking software
> 	  makes life a lot easier here. Also a compass if you don't
> 	  have a pretty good idea where South is.
>
> 	- Although it's not as bad at 2m as it is as 70cm, you'll
> 	  probably have to take into account the doppler effect
> 	  on the signal. Most satellite tracking software will
> 	  calculate the frequency difference for you on the fly.
>
> 	- To use satellite tracking software, you need up-to-date
> 	  Kepplarian elements for the orbits that you want to track.
> 	  These are realeased pretty much daily by NASA, but if they're
> 	  just shoving this thing out the door of the ISS, it might
> 	  be interesting trying to get hold of accurate ones for
> 	  the SuitSat ahead of time. They will need to be accurate
> 	  or the pass information will by out, sometimes by a lot
> 	  (i.e. you're pointing an antenna at entirely the wrong
> 	  part of the sky, 2 hours before or after the pass).
>
> 	- Much of the time of a pass is going to be <30' or so
> 	  off the horizon. Nearby trees and buildings are going
> 	  to get in the way. Football fields are good, but councils
> 	  can get upset if you drive your cars on them. The
> 	  football fields near Steves are good and flat, and also
> 	  surrounded by the river (which aparrently makes a good
> 	  ground plane).
>
> 	- Passes directly overhead are the best to use if you can
> 	  get them. They are longer, the doppler change is slower,
> 	  they are easier to track, and the object comes *much*
> 	  closer. Buildings don't get in the way as much.
>
> 	- SSTV stuff has lots of different standards. On the bright
> 	  side, there is lots of software, and it's quite easy to play
> 	  with even without using radios. Use a tape recorder, or
> 	  mobile phones or something to get a feel for it beforehand.
> 	  Ben, Bryden and I have gotten it to work over the wackest
> 	  connections. There is lots of software out there, just make
> 	  sure that the stuff you use does the mode the SuitSat does,
> 	  and isn't going to by crippleware.
>
> 	- The Amsat people, if given a choice will prefer orbits over
> 	  North America and Europe. Unless it's in a polar orbit,
> 	  Perth might not get that many passes. It might be a good
> 	  idea to record the audio off any passes you try for in
> 	  case you mis-time trying to decode it in real-time. It
> 	  might not work as well later, but might give you a chance
> 	  to try and do the SSB side of things when you're not
> 	  juggling everything else.
>
> If anyone is interested in doing this, i'm interested, but quite likely
> busy. I'm happy to lend stuff to help (I have a few antennas, feedlines,
> connectors etc. as well as the gear above). If you want to practice
> there are also am-sats already up there that operatate on 2M FM. Well,
> at least one.
>
> David
>
> [0] The axis that the electrical component of the E/M wave is travelling
>     along. CB etc is vertically polarised, so you put the antennas
>     vertically. TV is horizontally polarised, so you put antennas
>     horizontally. There is also circular polarization.
> [1] http://www.qsl.net/n9zia/cir_pol_rpt.html
> [2] This has led to concerned citizens calling the police previously.
>     Some people are just too easily spooked.
>