[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: HT uplink test via ISS? Keyboarders uplink test too.

On Tue, 22 May 2001, Vince Fiscus, KB7ADL wrote:

> Also, as a test, us straight keyboarders need to increase our power out in 
> order to determine how much ERP is required to overcome ISS APRS congestion 
> and interference from beacons. Recommend starting out with one hundred 
> watts into an eggbeater or beam, then digipeat a packet telling those 
> actually monitoring what you believe the best ERP to be to digipeat through 
> unattended APRS beacon interference.

Looking at ISS downlink logs, I don't see the justification for the above
comments.  What I observe on the ISS downlink over the USA over the last
few weeks is more like this:

1) I have not seen evidence that there are many unattended APRS packets.
2) I do see evidence that there are many TNC BEACONS set on automatic, and
although some of these use Gridsquares or include a positions report, the
packets are clearly not generated by APRS software.  Look at the header...
3) I think more than 80% of all packets are not APRS nor APRS generated.
Look at the logs.

APRS is very sharing of channel capacity.  Notice how over 3000
simultaneous users constantly share a SINGLE frequency in the north
american continent?  In any local RF area, from 20 to 200
can exist on the one channel.  Remember, APRS by definition was
designed for maximum channel sharing by a large number of users.

Conversly,a few MANUAL keyboarders can maintain a packet throughput that
can effectively saturate the ISS uplink...  Manual keyboarders can
generate about a packet every 3 seconds...

We both agree that there are too many automatic unattended beacons, but
the data proves that the vast majority of these are not APRS...

So we need to be careful about casting aspersions...  ALso, there is
nothing wrong with "automatic" generated packets during a pass at an
"attended" station.  Someone that sets his BText to what he wants to send
and sets BEACON to "1" (the highest rate possible in a KPC-3) will send
far fewer packets (1 a minute) than someone at a keyboard banging away on
the ENTER key (2 packets per second).  Similarly, WinAPRS and both kenwood
radios will only send one message packet a minute...

I do agree with you 100% that no one should be operating on the ISS
channel UNATTENDED no matter what the process without prior arrangmenets.
The key word here is "unattended".  The ISS PACKET system is designed for
live activity.  Only stations with operators should be on the uplink
during normal operations.

de WB4APR, Bob

Via the sarex mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe sarex" to Majordomo@amsat.org