From: makinc@hhcs.gov.au
Newsgroups: aus.radio.packet
Subject: Re: A broadcast service.
Date: 28 Jul 92 04:05:54 GMT
Organization: Aust. Dept. Health, Housing and Community Services

In article <terryd.711757277@extro.ucc.su.OZ.AU>, terryd@extro.ucc.su.OZ.AU (Terry Dawson) writes:

>>I actually didn't think of a FEC protocol I must admit, however
>>it would negate one of the major advantages of the idea, that is
>>it can be received with minimal equipment.
 
> I don't know baout that .. it would certainly preclude a dumb terminal
> hanging off a modem, but any sort of pc (in its truest definition) hanging
> from a modem would work fine.

Yeah but it requires specialised software.
 
>>Each message will have a message ID and, probably, a CRC (I
>>haven't decided yet).  Each message will be transmitted several
 
> I assume the CRC would also be sent in a printable ascii form and not
> as a binry checksum ?

I think so.  The Reuters stuff I'm reverse engineering at the
moment doesn't have it, but I'm waiting for the real spec which
has it fully detailed.
 
>>times over a 24 hour period so you will have a decent chance of
>>getting it.  I think the reduction of throughput by 2/3rds
>>(ie down to 800 baud), using some sort of AMTOR FEC mode but with
>>more bits, is too much of a penalty for the reliability it would
>>give.
 
> Why limit the system to 1200 bps ? Surely it is possible to squeeze a
> little more than that from a 7910/2206 type modem and a voice channel ?

aaarrrrggggghhhhhhh  Repeat after me, THIS IS A MINIMAL SYSTEM,
DESIGNED FOR BUGGER ALL EQUIPMENT AT THE RECEIVER!
 
> Ok, you're not keen on the FEC idea .. I can tell .. how about having the
> system alternate .. FEC/vanillla/FEC/vanilla .. ? Nah .. I don't think
> I like it either ..

phtuie
 
> What about a checksum/crc per line, instead of per bulletin ? .. I guess that'd
> be messy to read .. 

Yeah.  And why?  What is so earth shatteringly important that it
has to be totally perfect?  The only thing I can think of is
AMSAT Keps, and since the data is transmitted several times in a
day you can easily receive a couple of copies, or if the checksum
fails wait for the next broadcast, or log into the BBS and get it
via packet!
 
> Oh well .. it'll certainly be good for non-hams to monitor ..

<DING!>  He got it! :-) 

>>> I realise this would prevent people with 'dumb terminals' from making
>>> simple use of the thing, but would aid in sedning the stuff about
>>> in a relatively error free manner .. who uses a dumb terminal these days ?
 
>>Most packeteers. :-(

> Huh ?

Most people run dumb terminal programs for their
allsingingandalldancingIcandoeverything PK-292123453242MBX/PERCOLATOR
or run C=64s. :-(  For a basic setup they won't even have to
change software. 

> I'd prepare an article/project for publication in one of the _non_ amateur
> magazines .. ie Electronics Australia .. Silicon Chip .. whichever pays best
> and has survived the current current economic situation .. for people interestedin Amateur Radio but haven't gotten a license yet, it'd be a great resource :-)

Not until we have it running.  One local (Phil, vk1pc) came up
with the idea of using the local beacons as the transmitters. 
I'm going to chase up that route tonight! :-)

Carl.

-- 
Carl Makin, MVS/ESA Systems Programmer, VAX/VMS Dabbler. 
Dept. Health, Housing and Community Services, Canberra, Australia.
sserve.cc.adfa.oz.au!hhcs!makinc   -   UUCP
makinc@hhcs.gov.au		   -   Internet
vk1kcm@vk1kcm.act.aus.oc	   -   Packet Radio
"I'm from the Government and I'm here to help you."