Message-ID: <F4491236631044FC9C53742E1D817C69@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <4956BFEE.19110.2EE6D21@v.d.heide.on-line.de> <001601c968e6$912297e0$4201a8c0@home> <4957D4F8.9000709@telus.net>
In-Reply-To: <4957D4F8.9000709@telus.net>
Date: Sun, 28 Dec 2008 20:43:12 -0000
MIME-Version: 1.0
Importance: Normal
Subject: Re: LF: Re: WSPR and CW
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-1";
	reply-type=original
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Scott,,

JT65

I did a test with jt65 a while ago .. it stopped working about 3 db before 
the wspr .beacon  the K1JT version gave a s/n level about 3 dB better than 
the multipsk version ....not sure why as they where sent on alternate 
odd/even slots via the same sound card/tx system

The test encountered a little mid band qrm  from a mal adjusted cw beacon at 
the time , but the results are at

http://groups.google.com/group/uk500khz/web/jt65-a--jt2-tests

G ...

--------------------------------------------------
From: "Scott Tilley" <sthed475@telus.net>
Sent: Sunday, December 28, 2008 7:35 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: Re: WSPR and CW

>
> Hi Jim
>
> Interesting comments and its pretty much what I experience on WSPR HF.
> Another factor to consider with WSPR is the soundcard sampling rate it
> uses 12000sps.  Some have had issues with this as noted in a recent post
> on the WSPRnet blog:
> http://wsprnet.org/drupal/node/339
>
> This coupled with lack of time sync likely explains the issues
> encountered by 'super ham.'
>
> One thought would be to lengthen the sequence to deal with the 600m fade
> period OR allow WSPR to have an averaging function much like JT65.  With
> careful use of the average function in JT65 I was able to work many very
> small stations off the moon that would otherwise be impossible.  I bet
> the same would hold true for LF/MF and it would make all those not quiet
> good even sequences useful.
>
> Has anyone tried JT65 on 600m???  That should send 'super ham' spinning...
>
> 73 Scott
> VE7TIL
>
> James Moritz wrote:
>> Dear Klaus, Laurence, LF Group,
>>
>> I have been doing some experiments with WSPR on 2 PCs linked by audio
>> cables. I would certainly agree with KL1X about the importance of clock
>> accuracy - I found that an error of 5 seconds was enough to completely
>> prevent decoding. Fortunately, the clock on my shack PC is accurate 
>> enough
>> that setting it against an MSF-controlled clock once every several hours 
>> is
>> OK.  I also found that the "QSO version" of WSPR in WSJT 7 and the WSPR 
>> 1.01
>> beacon software will correctly decode each other's signals, although in
>> either case the QSO mode requires reception of all the overs of the QSO 
>> in
>> order to display the callsigns, due to the format used. When using the
>> beacon software for reception, be aware that it may take some minutes for
>> the decode to appear after the signal has been received - this seems to 
>> be
>> due to the "off line" nature of the signal processing used.
>>
>> Recent experience here is that the WSPR mode offers advantages compared 
>> to
>> CW, either manual or QRSS, on the 500kHz band due to the low SNR and the
>> fading experienced. Many signals are either always below the audible 
>> noise,
>> or not audible for long enough for aural CW copy without large numbers of
>> repeats. With QRSS, and a sufficiently long dot period, one can indeed
>> detect very weak signals, but the fading often prevents receiving, for
>> example, a complete callsign without losing some symbols and so also
>> requiring repeats. QRSS works much better on 136k, where the fading 
>> period
>> is much longer.
>>
>> WSPR certainly decodes signals that are too weak for aural reception. In
>> sensitivity terms, I think it is comparable to QRSS 3. WSPR has the
>> advantage over QRSS 3 that the message duration is shorter. The 2 minute
>> transmission period of WSPR is a reasonable match to the fading period
>> experienced on 500kHz, so there is a good chance of sending the message
>> successfully before the signal fades out. I have yet to see any readable
>> trans-atlantic CW or QRSS signals at this QTH, while copy of WE2XGR//2 
>> using
>> WSPR was reasonably consistent, producing a decode for about 25% of the
>> transmissions. The redundancy in the data should also make WSPR 
>> relatively
>> resistant to errors caused by QRN impulses, although the QRN level has 
>> been
>> low here recently. For beacon purposes, WSPR also has the huge advantage
>> that reception, logging and reporting is automated, so the operator can 
>> go
>> to bed sometimes!
>>
>> While WSPR does work well, I don't think it is the final word in LF/MF
>> digital modes - In particular, the information in a QSO is largely
>> restricted to "rubber stamp" exchanges. So I will certainly be interested 
>> in
>> trying other modes, and look forward to see the results of Klaus' work.
>>
>> Cheers, Jim Moritz
>> 73 de M0BMU
>>
>>
>>
>>
>>
>>
>>
>>
>
>



>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.176 / Virus Database: 270.10.0/1866 - Release Date: 
> 12/27/2008 20:49
>