RE: [amsat-bb] PACTOR on the birds

["Christensen, Eric" <CHRISTENSENE@xxxxxxx>]

While I agree whole heartedly with the statement "Best to operate in UI
mode..." there are times when connected packet is needed and not directly
with the bird, but rather through the bird, similar to what is being done on
INMARSATs.

73s,
Eric KF4OTN



-----Original Message-----
From: Robert Bruninga [mailto:bruninga@usna.edu] 
Sent: Tuesday, 11 April, 2006 17:46
To: amsat-bb@amsat.org; Christensen, Eric; andre@pe1rdw.demon.nl
Cc: fieldops@amsat.org
Subject: RE: [amsat-bb] PACTOR on the birds

>>> "Christensen, Eric" <CHRISTENSENE@ECU.EDU> 
>So how would one do a connected packet via 
>an amateur satellite?

The best way is by using the PACSAT protocol.  

FOr conventional connections, the 1-ack-per-packet
CONNECTED packet format is very inefficient via satellite
and a waste of bandwidth on a busy uplink channel.  In
most cases, the ACK is not needed since the SENDER can
see his digipeated packet and have a good idea that 
the receiver got it too.  Its getting digipeated is where the
problem is, and adding ACKS to that problem only makes
things worse..

Best to operate in UI mode and sned retries when a given
packet is not digiepated...

de Wb4APR, Bob



I don't think that PACTOR is 100% duty cycle.  Compared to the bandwidth
that is available on some sats it would take up a very small sliver of the
bandwidth.  Or are you looking at duty cycle in a different way?

I could see the Doppler correction being a problem but if it were computer
controlled couldn't you correct that fast?  And if the connection wasn't
being used on a LEO the Doppler wouldn't be that fast, right?

Eric KF4OTN


-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org] On Behalf
Of Andre v Schayk
Sent: Tuesday, 11 April, 2006 13:32
To: amsat-bb@amsat.org 
Cc: fieldops@amsat.org 
Subject: Re: [amsat-bb] PACTOR on the birds

Christensen, Eric schreef:

>Can anyone tell me why I couldn't use PACTOR a satellite, given I had
enough
>room, etc...  Trying to think out loud.
>
>73s,
>Eric KF4OTN
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>
The reason is twofold, a technical one and an operational one.
The technical one is that pactor is not dopler tolerant, the tolerace
for pactor 1 is less then 80 hz, I think pactor 2 and 3 are even more
critical.
The operational problem is that it is very bad practice to use a 100%
dutycycle mode on most linear sats, some will alow psk31 sstv and other
modes but most don*t.

73 de Andre PE1RDW
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