On address fields in AX.25 packets
 

Hi,

I am currently implementing a TNC following the specs in the v2.2 AX.25
protocol. Platform: An ATmega32 microcontroller. Will be a neat, little
package when I'm done.

Anyway, as I am rather tired now and the AX.25 paper appears to have
no other answer than "impossible" to my problem, I have a question
for this forum:

What if I wish to put a seven character callsign in the address field?
True, seven octets are reserved for each callsign, but one of these is
for the SSID. Can it be done?

What happens if I extend the source address field to eight octets?

Dependent on the TNC at the receiving end?

Will the last character simply be discarded?

Will the frame get rejected as not correctly formatted?

This problem is not hypothetical. The target application is a picosatellite
which has been assigned (Tentatively, at least) a seven-character call.

Perhaps I'd better spend my time talking the post- and telecom authority
into giving us a six-letter call, rather than trying to work my way
around a protocol limitation... :-)

--
73 de LB1LF

Odd Erling, ARK

"Das Lied schläft in der Maschine" -Einstürzende Neubauten

In Ham radio we can use a tactical address (LAX-1, SPACE-1), etc.
I would just use something like that, and then ID the transmission via
the payload data, such as "LB1LF Space Satellite"

In Ham radio we can use a tactical address (LAX-1, SPACE-1), etc.
I would just use something like that, and then ID the transmission via
the payload data, such as "LB1LF Space Satellite"

Gene Storey wrote:

In Ham radio we can use a tactical address (LAX-1, SPACE-1), etc.
I would just use something like that, and then ID the transmission via
the payload data, such as "LB1LF Space Satellite"

-I was thinking of doing it like this - just curious as to if it was
possible to put a longer call into an address field. Working packet abroad,
for instance - RA3A/LB1LF will hardly fit into six octets... :-)

The tactical address, btw, is NCUBE-1, assigned call is LA1CUBE.
(See www.rocketrange.no/ncube if interested - unfortunately,
there is not much information on the amateur payload. In short, the
secondary objective of the satellite will be 9k6 digipeating. Depending
on how much memory is available after all the programming is done, perhaps
limited store-and-forward capability will be added as well.

Thanks for your input. Hopefully AMSAT will respond to my enquiry as
well. There are quite a few details to work out if one wishes to do it
all by the book. :-)

--
73 de LB1LF

Odd Erling, ARK

Sleep: A completely inadequate substitute for caffeine.

Gene Storey wrote:

In Ham radio we can use a tactical address (LAX-1, SPACE-1), etc.
I would just use something like that, and then ID the transmission via
the payload data, such as "LB1LF Space Satellite"

-I was thinking of doing it like this - just curious as to if it was
possible to put a longer call into an address field. Working packet abroad,
for instance - RA3A/LB1LF will hardly fit into six octets... :-)

The tactical address, btw, is NCUBE-1, assigned call is LA1CUBE.
(See www.rocketrange.no/ncube if interested - unfortunately,
there is not much information on the amateur payload. In short, the
secondary objective of the satellite will be 9k6 digipeating. Depending
on how much memory is available after all the programming is done, perhaps
limited store-and-forward capability will be added as well.

Thanks for your input. Hopefully AMSAT will respond to my enquiry as
well. There are quite a few details to work out if one wishes to do it
all by the book. :-)

--
73 de LB1LF

Odd Erling, ARK

Sleep: A completely inadequate substitute for caffeine.