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Re: Why FULLDUPE On is good? (Re: iss)

> Hello all. This is Yoshi.JF6BCC.
>   So waht is the advantage of FULLDUPE mode on ISS ?  Is there any
> good reason to choice it?


The Full Duplex mode on the ISS TNC would allow it to ignore the DCD 
status that prevents it from transmitting due to a busy channel.

Ground stations should not use Full Duplex, because the ISS TNC
cannot hear you when it is transmitting.

With the number of stations in the US transmitting on this side of the
world you would expect the TNC to be digipeating packets very quickly.
This is not the case as we have observed.  With the Full Duplex mode
activated, the digipeater would ignore the busy channel on its input and
immediately transmit the packet.  It is true that there may be a packet
immediately behind it that could be lost, but the efficiency could possibly
be improved in the digipeat mode.  I say possibly because there are
many stations on the ground competing to be decoded by the digipeater.
This interference prevents the ISS TNC from decoding very many packets.

It is unfortunate that the Pico Packet TNC does not have a remote 
management feature so that a designated ground station could 
reconfigure the unit.  It would be nice if PacComm could burn an EPROM 
for the unit with default parameters.  Kantronics does make a TNC that 
can be remotely managed.  A remote management feature would ease 
the burden from the Astronauts busy schedule to manually make these 
changes in the TNC.  Since the Pico Packet is flight certified, it may
be easier to replace the EPROM.

I will have to try burning a UIDIGI EPROM and see if it works in my Pico
Packet.  If it does, then there could be a solution to replace the Pico
Packet EPROM with a UIDIGI firmware that would allow the Pico Packet
to have remote management capabilities from the ground.  A UIDIGI
EPROM can be burned with all the default parameters required.  This
is what we use for APRS digipeaters in my area and they work very
nicely.  I would be happy to burn a UIDIGI EPROM for the ISS TNC if it
works in the Pico Packet and they could install it.


Tim - N8DEU
Huntsville, Alabama

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