Order Tray | Contact Us | Home | SIG Lists

[aprssig] RE: 6 meter APRS or meteorscater?

Robert Bruninga bruninga at usna.edu
Wed Jan 23 21:44:04 UTC 2008


Found some background on Meteor Scatter today.

It looks like packet rates are on the order of one packet per
minute or so.  But this assumes point A to point B.  When we
assume that we have a dozen or more point-B's, (by adding many
6m receivers to the existing national network of APRS Igates),
then the performance would multiply to something like a packet
every several seconds (on average)!  For an EmComm method of
getting Email out of a situation area, that's pretty good. 

Here is our project:
http://www.ew.usna.edu/~bruninga/meteors.html

Oh, also found that the daily reliability is worst at 8PM and
best at 8 AM by a factor of 3 or so.  And annual reliability is
worst in February and best in the summer by a factor of 4 or so.
But the message still gets through.

Here are some data points I got out of some old reports.  Notice
the 4th example when 4 receivers were added!

* 600 mi, 2 kbd, 200W, 1 RX, 10+10dB antennas, worst case wait
time was between 1.3 to 3.3 minutes for a 150 byte message at 38
MHz.

* 500 mi, 2 kbd, 400W, 1 RX, 10+10dB antennas, worst case wait
time was between 1 to 4 minutes for a 50 byte message at 38 MHz.

* 1000 mi, 2 kbd, 400W, 1 RX, 10+10dB antennas, worst case wait
time was between 2 to 8 minutes for a 50 byte message at 38 MHz.

* 600 mi, 2 kbd, 2Kw, 4 RX, 2+10dB antennas, wait times 3 to 10
seconds for 130 bytes at 38 MHz

* 400-900 mi, 2kw, 8+14 dBi, 15 to 48 secs for 130 bytes at 38
MHz

* 600-1200, 750W, 2Kbd, Dipole +13 dBi, 2 to 5 minutes for June
46 MHz, PSK, -126 dBm for 15 bytes.

Again, looking at using simple 100 to 200' long wire antennas,
to keep the RX sites simple and un complicated.  Belly-scatter
by aircraft also helps...

Bob, WB4APR

> -----Original Message-----
> From: Robert Bruninga [mailto:bruninga at usna.edu] 
> Sent: Wednesday, December 19, 2007 5:56 PM
> Subject: RE: [aprssig] RE: 6 meter APRS or meteorscater?
> 
> Here is more of the idea for an APRS meteor Scatter first
> response communications system:
> 
> 1) I already mentioned adding 50.63 MHz receive monitors
running
> 1200 baud APRS to many strategic Igates.  This listens 24/7
for
> outgoing emergency emails from the affected area.
> 
> 2) How about we use 2 meters, 147.585 at 9600 baud to throw
any
> emergency response traffic back into the area...
> 
> Using 100 Watts, a good beam pointed at the affected area from
> about 500 miles away, and then continuously beaconing any
needed
> APRS one line messages back into the area at 9600 baud, would
> let anyone driving around in the area possibly receive this
> traffic on their D7 or D700 radios without having to keep a PC
> runnning.
> 
> We have demonstrated that 6m works great, and 2m can work
during
> meteor scatter, so this is an area ripe for experimentation.
I
> think the 6m will work fine.  But we need people to test the
> success rate of forcing a message into an area using 2m.  And
to
> determine if 9600 baud is that much better than 1200 in this
> case...  
> 
> It is the one-hand-clapping advantage of APRS that can help
make
> this testing more successful.  Receivers just inject into and
> Igate,  Then Transmitters test at will.  When the other end
> receives their packet, they can see it themselves on the
> APRS-IS.  For this test, then I would receommend transmitting
> every single packet with a unique serial number embedded in it
> so that the APRS-IS dupe filters will not filter out all the
> successes.
> 
> Any teams want to start testing?
> 
> Bob, WB4APR
> 
> > -----Original Message-----
> > From: aprssig-bounces at lists.tapr.org 
> > 
> > >> Since Meteor scatter is a continuous statistical
> > >> process, then as long as the outgoing message has 
> > >> been in the TX queue for X minutes, then there is 
> > >> a 99% probability that it was received and injected 
> > >> into the internet.  Done.
> > >>
> > >> We can experiment to find out what X is.
> > >> One X for using a 2 dBi gain vertical and 
> > >> another X for using a small beam.  
> > >
> > > Huh??   How would you aim a beam at randomly 
> > > occurring events? 
> > 
> > Say if you were in New Orleans, you would point your beam
> > towards the highest density of potential listeners that are
> > about 500 to 1000 miles away.  That is the optimum range for
> MS.
> > So I'd point towards the Eastern Seaboard.  Then hammer
away.
> > See my meteor.txt with the original APRSdos:
> > http://www.ew.usna.edu/~bruninga/meteors.html
> > 
> > > I'd be ready to give this a try...here in the 
> > > greater L.A. area,  weak-signal 6M receive is 
> > > totally buried under 50-100 uV of lower-sideband 
> > > "grunge" from channel 2 ...
> > 
> > You could still make a great TX site for the TX end of the
> > test...
> > Bob, WB4APR





More information about the aprssig mailing list