From: ees1mw@EE.Surrey.Ac.UK (Mike Willis)
Newsgroups: rec.radio.amateur.misc
Subject: Re: Packet, Clover, Piccolo, bandwidth.
Date: 27 Aug 92 08:43:49 GMT
Organization: University of Surrey, Guildford, UK.

In article <9208261537.AA19587@swgen-t> pjml@swmis.nerc-swindon.ac.UK (Pete Lucas) writes:
>Seems to me that we have a problem! This months RADCOM has a diatribe
>against HF-packet written by some Antipodean type.
>
>I accept that HF packet as currently practised is *not* good, but i dont think
>AMTOR is an answer. AMTOR is a byte-oriented protocol; therefore it
>limits the nature of what can be sent. Normal AMTOR has uppercase letters,
>figures, minimal punctuation. Thats it. Even worse than conventional RTTY!
>
>What is needed is a protocol that is not byte-oriented, so we can use it to
>ship binary files, and non-ASCII text; then it could handle cyrillic, Kanji
>etc. with few problems, as well as fax.
>
>The method of encoding; PSK is not good (for all the reasons already
>discussed). Something like Piccolo is far better; this was *designed* to
>be used on noisy HF paths with the S/N ratio being unity or less! Problem is,
>the installed user-base of TNCs. Not a lot can be done about this, unless
>everyone runs out and buys Racal LA1117 Piccolo-modems.
>
>perhaps its time for a change in bandplans too; surely manually generated
>CW is just as much a 'digital' mode as packet, RTTY, Amtor etc?
>A packet station on 28.245MHz would help get some of the intruders to give
>up & go back whence they came.....
> 
>       -Pete Lucas- G6WBJ - pjml@swmis.nsw.ac.uk@nsfnet-relay.ac.uk

Well firstly, packet is totally unsuited to HF in its current standard.

No, apart from getting rid of all the old guard at the RSGB, (having met
some of them, I know what they are like.), what we need is a form of
forward error correction appled to packet. We also need a more efficient
modulation scheme than the FSK currently used. PSK would be a start.
Modern DSP modems can make all kinds of compensation for noise and
non-linear channels, and can adjust in real time. We also must get round
this silly 300 baud limitation. Most of the world is not America and
couldnt care less what the FCC say. How about trellis coding?
Reed-Soloman? Interleaved Convolutional or a combination to take care of
the FEC, plus positive ack for the lost packets. 64 level phase/amplitude
coding would allow us to send 6 bits per Hz, With 200 Hz bandwidth plus
filtering taking up a channed of not much over 300 Hz we could have 1.2
kb/s. Allowing for coding overhead at say 50% (but make it variable to
account for good/bad channels) that would give us 600b/s data rate. Still
slow but much better than Amtor.

What we really need is a standard. The hardware is already available from
the likes of LL-Grace and AEA. I am sure Bob could provide the software
for the Modem, if he can decode space probes at many dB below the noise, a
APSK modem should not be to hard. A PC can quite happily manage the 
coding/decoding.

The other thing we need to get away from is the resistance to change and
the fixed ideas that are choking the hobby. 

Mike
From: alanb@hpnmdla.sr.hp.com (Alan Bloom)
Date: Fri, 28 Aug 1992 00:19:26 GMT
Subject: Re: Speaking of Q-Codes...
Organization: Hewlett-Packard, Santa Rosa, CA