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Re: Hey did you know that . . . .

>Echo/AO-51 turned 1 year 4 days ago?.... Now, I 
>wonder when will we see  Echo's UI digipeating....
> ...[and] a way to link with the Kenwood radios.

There is no technical reason why digipeating cannot be 
enabled.  It is probably just a matter of priorities on the 
busy command team.   The ECHO web site says:

>>Due to restrictions in the Satellite, there can be 
>>no digi... on Echo at this time.....  Echo ...
>>will only pass AX.25 packets beginning with a 
>>certain character... 'P'...  Therefore, the digi 
>>packet will not get through the SCC unless the 
>>destination station call sign begins with... 'P'.

But a UI or any APRS packet can be addressed to 
any special callsign (In APRS it is called an ALTNET).
Any packet user (including APRS) can just set their
AX.25 destination (or ALTNET) to something like 
"PECHO" and the problem is solved.  If ECHO has 
the digipeat bit set ON, then digipeating via one 
of the shared digital uplink channels probably could

Note that this restriction of addressing the packet
to a address starting with a "P" will prevent POSITS
from the D7 and D700 or any MIC-E packets, from 
being digipeated because the packet then begins
with the first digit of latitude.  But, it will allow those 
radios in MESSAGE mode to send and receive APRS 
messages from radio to radio if they set the right 

Note:  (if you change your UNPROTO in the kenwood,
write it down first, since it shows your version
number of the firmware in your radio and you will want 
to restore that when not trying to digi via ECHO.

Don't forget though, that ECHO is 9600 baud so 
normal terrestrial TNC's at 1200 baud wont work.
But the D7 and D700 with their built-in 9600 baud
TNC's are perfect for this application.  I assume the
Alinco with built-in TNC will also work, but it will
need an external PC to interface to the human op.

I think this will be a great capability and will not
interfere with normal FM and other experimental
modes on ECHO.  UI digipeating can share the 
9600 baud digital channel which is ON most of the 
time anyway.

In fact, we can get around the "P" restriction
even for position reports by simply shifiting 
our LATITUDE digits to the right one space.
ANy latitude below 10 degrees already begins
with a "P" in the Mic-E format used by these
radios.  So instead of entering DDMM.HH for
latitude, simply enter 00DD.MM and this position
can be properly interpreted on receipt.

If eventually this "P" restriction could somehow 
be expanded by just a few more digits, (I have 
been told this is not  currently possible with 
existing firmware and hardware on ECHO)  then:
  "A" would open it up for ANY APRS packet
  "R" allows D7/700 POSITS in latitudes 20-29
  "S" allows D7/700 POSITS in latitudes 30-39
  "T" allows D7/700 POSITS in latitudes 40-49
  "U" allows D7/700 POSITS in latitudes 50-59

and so those 5 additional characters, if they could
somehow be permitted, would open up ECHO to 
support handheld and mobile satellite communications
on the digital channel, with minimal impact on any
other uses of the satellite.

Hopefully one day, the digi bit can be enabled
for an experiment to see how well this works.

de Wb4APR, Bob
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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