[amsat-bb] A refresher needed...

[Daniel Estévez]

El 02/12/15 a las 04:00, Mark Lunday escribió:

Hi Mark,

Lets try to answer some of your questions.

> 1.	Based upon the AMSAT page, I conclude the following birds are
> active: ISS (FM), LILACSAT-2, AO-73, AO-85, SO-50, NO-44, NO-84, FO-29,
> XW-2F, AO-07.

Yes. However, LilacSat's transponder is only active some days, as you
can see. Also, NO-44's health is not very good and its giving several
problems. I hear that, for instance, it shouldn't be used over Region 1
(Europe and Africa) to prevent it from transmitting on 144.390 (which is
used by meteor scatter people).

> 2.	At the top of the AMSAT satellite status page, there is a blank line
> for satellite status, with reports.  Is this a new satellite that is not yet
> turned over to operations?

That's probably nothing. Reports not correctly labelled or a software bug.

> 3.	Which of the following satellites will work when NOT illuminated?  I
> remember AO-7 and NO-44 won't, and AO-73 will, but not sure about SO-50,
> FO-29, NO-84, AO-85, XW-2F.

AO-7 only works when illuminated. NO-44 I'm not sure about its status.
As I said, it's not doing so well. The rest of them work fine in eclipse.

Also, note that on weekdays AO-73 will only run high-power (300mW)
telemetry when illuminated and transponder and low-power telemetry when
in eclipse. In weekends it's always transponder and low-power telemetry.

> 4.	What is the best way to tell if a satellite is illuminated?  Could
> be before sunrise at my QTH if the bird is east, or after my sunset if the
> bird is west.  How can I tell?

In fact a satellite can be illuminated even if it is over the nigh side
of Earth, because it high above the surface. For instance, AO-7 will
spend about half of the year always illuminated.

If your satellite tracking software doesn't tell you (Gpredict) does,
you could use Illum by DK3WN. Look for it here:
http://www.dk3wn.info/software.shtml

> 5.	I need more info on APRS.  I set it up to relay my position from my
> car on 144.39 many years ago, but Bob Bruninga has often said APRS capable
> of so much more.

You can send text messages, get weather reports, send "objects" for
locations of interest, etc. Take a look at http://aprs.fi to see what
other people are doing with APRS.

> a.	Is satellite APRS helpful just for isolated locations, for relaying
> information?

Not sure. Probably most people use it just for playing. You can do valid
DX QSOs by satellite APRS if that's your thing, also.

> b.	How long does the satellite transmit the information packet (what is
> the lifetime of the packet?)  

The satellite retransmits the packet almost immediately after receiving
it and only one time. This is the same as a terrestrial digipeater does.

> c.	What if the amount of packets to be transmitted by the satellite
> takes longer than the visibility of the satellite at my QTH?  I won't hear
> certain data, right?  

As I said, the satellite doesn't do store and forward, but rather
repeats the packets immediately. What happens if many people are using
the satellite is that the packets will collide and won't be heard by the
satellite. The same happens with a terrestrial digipeater.

> d.	What is everyone else using satellite APRS for?

As I said, probably just for fun, but perhaps there are people in remote
locations using it for relaying some useful data (although you probably
could also use HF APRS for that).

Hope you find this useful. Probably other people can add more
information or another point of view.


73,

Dani M0HXM/EA4GPZ.