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

[Dr. Gerald N. Johnson]

I've seen commercial satellite data modes using some QAM mode years ago. 
I don't remember but it seemed to be more than 16, maybe not as many 
points as 64. Perhaps 36QAM.

But probably not in 3 kHz bandwidth either.

JT modes swap signal strength for forward error correction and data 
speed including some hinting from stored data of what calls might be 
heard. Some think there's a bias there that sometimes the software makes 
contacts out of noise.

73, Jerry, K0CQ

On 4/29/2011 7:32 PM, Marciniak, Ed wrote:
> 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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