[NLRS] higher speed packet - Was RE: Important matter for VHFers

[Marciniak, Ed]

Consider that a DSL modem might give something like 7-8 bits/Hz, but at a S/N ratio of 30+ db, doesn't have to deal with selective fading from motion of the transmitter/receiver or scatterers in between, and can analyze the channel at initialization with the assumption it doesn't change over the life of a session. The obstacles are formidable.

Theoretically, JQAM ( http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=18491 ) can provide high data rates per bandwidth with 16QAM and 64QAM. I haven't run into anyone running it. Has anyone on the list here?

(Approximately, the theoretical limits for 16QAM and 64QAM, are somewhere in the 20 and 25db range respectively with a bit of forward error correction applied and the bit rate adjusted to compensate)

-----Original Message-----
From: nlrs-bounces at mailman.qth.net [mailto:nlrs-bounces at mailman.qth.net] On Behalf Of tom ring
Sent: Monday, April 25, 2011 9:15 PM
To: Dr. Gerald N. Johnson
Cc: 'nlrs at mailman.qth.net'
Subject: Re: [NLRS] Important matter for VHFers





On 25 Apr 2011 at 14:07, Dr. Gerald N. Johnson wrote:

<snip some good comment>

> If we worked at it we could get higher speeds than 9600 in 15 KHz
> bandwidth. It would take multiple tones like land line modems that get 
> nearly 56 KB in less than 3 KHz bandwidth. It would take serious modem 
> modifications to accommodate varying pass bands without having to 
> negotiate phase and amplitude equalization for each transmission. 
> Probably would have to use complex forward error correction.

And it's all been done if it's possible with present technology.  The only 
question is how much is patented, how much is already open source, and how much 
is secret.  The sets will overlap.

tom
K0TAR

> 
> >
> 73, Jerry, K0CQ
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