Message-ID: <4F247AE2.2080306@iup.uni-heidelberg.de>
Date: Sat, 28 Jan 2012 23:46:58 +0100
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <3992CC59F7A14AA694628529761EC5DE@AGB>	<4F1F695F.7020400@charter.net> <CAA8k23Rm-kX4nz4nOcaD6Rrbh7-cd+OiP1Jra+SVHriaFwdcMQ@mail.gmail.com>
In-Reply-To: <CAA8k23Rm-kX4nz4nOcaD6Rrbh7-cd+OiP1Jra+SVHriaFwdcMQ@mail.gmail.com>
Subject: Re: LF: WOLF DATA MODE S/N FIG ?
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1d40d84f247b351f72
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


...so Andy, would you suggest it may be useful even on VLF, where the 
phase is rather stable over a longer time?

73, Stefan

Am 28.01.2012 20:18, schrieb Andy Talbot:
> I've been thinking about the maths behind Wolf and it gets quite interesting.
> One thing we can say, its definitely a spread spectrum system !!!!!!!!
>      SRI USA Hams :-(
>
> A message of 15 characters taken from an alphabet of 40 (A-Z 0-9 and a
> few punctuation) give 80 source bits of data after compression.
> These are expanded to 480 data bits in six parallel tail-biting
> convolutional encoders.    In pure error correction terms this seems
> like mega-overkill, so there's more than meets the eye going on...
> Interleaving may or may not then be employed, but it doesn't affect
> things.
> The 480 bits are then merged with another 480 bits of a PN seqeunce
> (in a not totally dissimilar way that I suspect Opera does) to allow
> the decoder to lock to the sequence.
> The whole lot is then transmitted at 10 Symbols/s BPSK so the whole
> message takes 96 seconds
>
> The underlying data is 80 bits, so without any sequential merging, to
> a rough approximation it equates to about 1 bit every 1.2 seconds, so
> you could say the effective bandwidth is 0.833Hz and the very strong
> FEC will allow something like +2 to +3dB S/N for decoding in this
> bandwidth.    So therefore something like 3dB up on WSPR, and about
> the same as OP8 with the same mean power.   (I know PSK and FSK don't
> have the same noise performance, but just ignore the details for now!
>   There's probably a couple of dB in it when signals are weak)
>
> But its not this simple.  Being a fully coherent system, and unlike
> WSPR/JTxx/Opera and any other non-coherent mode, successive messages
> can be overlaid.  They can even be used as part of a soft decision
> decoding tree, and theoretically could go on for ever -  providing it
> is possible to maintain synchronisation.
>
> So by continuously looking at repeated message, the effective
> bandwidth will get lower by the average of the number of times it has
> been repeated.   Two repeats 3dB or half BW, 4 repeats 6dB , 8
> repeeats 9dB  etc etc
>
> Does this seem about right ?
>
> Andy
> www.g4jnt.com
>
>
>
> On 25 January 2012 02:30, John Andrews<w1tag@charter.net>  wrote:
>    
>> Graham,
>>
>> There is no single s/n figure or specified BW in which to measure it. WOLF
>> works by building copy up over a period of time, and assuming good
>> frequency/phase stability, a half hour or more is practical.
>>
>> The data rate is fairly fast, 10 b/s, with a 960 bit message, so that a
>> complete frame of data is sent in 96 seconds. You get three quick reports in
>> the first 96 seconds, and then decodes every 96 seconds after. Each message
>> is 15 characters, with no rules about callsign format.
>>
>> Tests done some years ago show it roughly equivalent to QRSS60 in terms of
>> signal level. It does give some clues as to whether a signal has been
>> locked-in, and has the possibility of partial copy, unlike some "all or
>> nothing" modes. Fifteen characters in a half-hour is of course much faster
>> than QRSS60 would permit. 2-way QSO's are fairly easy with some advance
>> agreement on what to do with the 15 characters.
>>
>> The downsides are the need for a linear transmitter system (as this is PSK),
>> receiver/transmitter stability and frequency accuracy. It works at 600
>> meters, but is fairly useless at 160 meters and up.
>>
>> The newest version is by DL4YHF, and may be found at:
>> http://www.qsl.net/d/dl4yhf//wolf/ .
>>
>> Note that this version has 5 b/s and 20 b/s variations. Testing has shown
>> that the program tends to provide copy in the same amount of time, so
>> there's no overriding advantage to either.
>>
>> John, W1TAG
>>
>>
>> On 1/24/2012 7:27 PM, Graham wrote:
>>      
>>> WOLF DATA MODE S/N FIG ?
>>> Long time since I used wolf , anyone have the
>>> expected decode min s/n level ?
>>> and now what s/n was ref to , as changes
>>> may of taken place over time
>>> Tnx -G.
>>>
>>>
>>>
>>> No virus found in this incoming message.
>>> Checked by AVG - www.avg.com
>>> Version: 8.5.454 / Virus Database: 271.1.1/4162 - Release Date: 01/23/12
>>> 19:34:00
>>>
>>>        
>>