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Re: Mobile 9600 Baud SOLUTION!




Hi Bob,

As I remember, the read-my and list-my features were implemented before
the PACSAT broascast protocol came to life. At that time we had to use the
DOS application PG (not PB) to download the directory and/or files. There
was a choice to download only my-files. It was a feature that was
implemented using ax.25 in connected mode, thus very inneficient if many
users were trying to use the spacecraft. When the PACSAT broadcast
protocol was implemented, it was decided to keep the search-and-request
capabilities on the ground to simplify onboard software. The tradeof was
the need to download the directory. The net gain was very positive
compared to the old method. Another problem with some older spacecrafts
was the limited amount of code memory. Many features could not be
implemented due to the lack of memory space. Also, the time required to
search through the directory to select files for a specific user was
something to take in consideration.  Given that and probably few other
reasons, the complexity was left to the user software on the ground. 

I would strongly agree that the PACSAT broadcast protocol on both downlink
and uplink (read the NUP) have improved the overall eficiency of the
communication system. The PACSATs did also make full use of the natural
broadcast characteristic of radio waves (specially for satellite
communications). 

What we need now is more ideas and volunteers to implement new features on
both spacecraft and terrestrial software. Indeed there are limitations on
how much can be done with the active spacecraft software, but new birds
will eventually fly and new software will have a chance to be used. In
order to make it possible we should develop, test, test, test, and test
software on the ground. We need testing platforms (hardware) and joint
cooperation between the various developers, and the amateur satellite
community. I believe we have a vast field of experimentation and
development. We need new protocols and new applications. The current
hardware is still fine for many applications. We need software and we have
to write it ourselves. Any volunteers for a open project?

73,

-- Edson, N1VTN

On Sat, 7 Nov 1998, Bob Bruninga wrote:

> > Bob Hart said: Thanks to all [re: his query about Mobile PACSAT antennas]
> > There were many thoughtful and interesting ideas, but no "Silver Bullet".
> > It appears  the descriptors "mobile" and "9600 baud" are mutually exclusive
> > ... the PACSAT Protocol ... expects you to [capture] the directory
> > and any downloads. If you miss a bit here and there during a pass, [your
> > station must request] fills for the holes ... [BUT] if the antenna is
> > marginal and you miss lots of bits you end up using all the subsequent
> > passes requesting fills. Meanwhile you [have missed new Directorys with
> > more traffic and] things [only] get progressively worse...
> 
> BINGO!  THE SILVER BULLET is to IMPLEMENT the most important function
> which is IN THE PROTOCOL, but never impelmented. And that is the ability
> to LIST-MY or READ-MY messages.   Then who cares about the directory. AND
> a marginal antenna will werk perfectly.  You just wait until the OVERHEAD
> Pass (6 per day) for all three satellites and your mobile ?turnstile?
> antenna will be more than adequate for the few minutes you need.   THus,
> anyone with a dual band FM radio can go PACSAT MOBILE easily for the
> purpose of sending and receiveing their own messages.
> 
> I know that no one wants to mess with the software on a *working*
> satellite, but we must make sure that any NEW PACSATS implement the
> LIST-MY and READ-MY capablility or we are shooting ourselves in the
> foot...
> 
> de WB4APR, Bob
> 
> In otherwords, the Hardware designers of the pacsats DID make a
> transmitter and receiver that was capable of working with OMNI antennas,
> but back in 1992 the emphasis was on BULK delivery of all the BBS traffic
> and BULLETINS.  The resulting PACSAT protocol works perfectly for this
> with dedicated GATEWAY stations and gain antennas, but the omission of the
> READ-MY  capability completely obviates the mobile users WHICH IS HARDWARE
> CAPABLE.  Its a software issue.  BUT... I fully understand the reticence
> to mess with a working satelite, but we for sure must not launch any new
> satellites with this omission.  LIST-MY and READ-MY are essential commands
> in the 1999 and next century... (considering that MOBILE operations is
> about the only AMATEUR radio digital mode that can compete with the
> Internet)...
> 
> Just wait until after December when anyone with a Kenwood 9600 Baud HT can
> copy the downlink, and then finds out that the satellite is useless to
> them...
> 
> I was writing a long dissertation on this problem and will post it later
> tonight...  But this message is the essence in a nutshell...
> 
> bob
> 
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