Message-ID: <FB4E7A1FEC7143429E593AAC25E90D32@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <4AAB7F2D.25346.12CA10F@dave.davesergeant.com>
In-Reply-To: <4AAB7F2D.25346.12CA10F@dave.davesergeant.com>
Date: Sat, 12 Sep 2009 14:08:43 +0100
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Subject: Re: LF: WOLF/WSPR Sound card issues
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Dave,

I'm not sure if the  actual frequency error is critical to the  wspr system, 
from the problems I experienced last year with the  system, as the  quality 
of the  received transmission in terms of  signal to  noise was identified 
as the 'only' factor that determined the  ability of the  system to  decode.

As the  data would appear to be' array processed' with decodes extracted 
from a received 2 dimensional block of data, any frequency error is not 
significant, however it was discussed that the  possibility existed that the 
exact time interval of the  symbolisation 'frames' may be truncated by a 
sound card clock running 'fast'

This was proposed as an explanation to the  observed situation, where a 
strong constant  signal, resulting in the  reception of  a full set of  sync 
frames failed to decode, where as a signal from the  same station, 
considerably weaker either by a power  reduction or coinciding with a deep 
qsb fade produced a reliable  decode to the  systems lower  operating limit. 
By off air measurement of the  time frame, it  could be  observed that the 
transmission finished  some 2 seconds before the  end of expected period. 
switching to a usb card and re running the  test, resulted in the  correct 
time frame and 100% decode of a 'clean' stable signal.

The Initial card   M-Audio delta-4  ,  substitute card ADS-rdx-150, 
interestingly I have  used the  44khz AWE-64  isa soundcard for wspr 
recently and where as long range decodes looked to be reliable, Gary g4wgt 
who is some 25 miles , has noted a high percentage of failed decodes , but 
not a total failure as when the  delt-4 was used.

May be (we hope)  later  issue of wspr will have a clock check facility?

G .







 --------------------------------------------------
From: "Dave Sergeant" <dave@davesergeant.com>
Sent: Saturday, September 12, 2009 11:59 AM
To: <rsgb_lf_group@blacksheep.org>
Subject: LF: WOLF/WSPR Sound card issues

>
> I have been trying to work out why I have such bad copy of WOLF and
> WSPR (on HF as well as 500kHz) and others report it as 'plug and go'
> and came across a page at http://wsprnet.org/drupal/node/336 which
> explains the problem exactly. It seems that both WOLF and WSPR are
> designed for current sound cards which have 48,000 and 96,000 clock
> rates. Mine is obviously from the old stable so has 44,100 etc rates.
>
> For information it is the sound card interface built into the
> motherboard, an ASR Rock K7S41GX dating from 2003 with generic AC'97
> sound. Zilch more given about its spec in the manual.
>
> I did a test using a 40m broadcast carrier on 7355kHz, with the K2
> tuned to get a 1.5kHz tone.
>
> Argo reports it correctly at 1502Hz, pretty spot on
> Wolf (default 8000Hz sampling) reports 1553Hz
> WSPR (2000Hz sampling) reports 1534Hz
>
> Obviously the interpolation works differently for the different
> sampling rates of WOLF and WSPR but the effect is obvious.
>
> Being an older card there is no way it will support the 48,000 etc
> sampling rates natively, and there is certainly no switch. In Wolf I
> can play around with the calibration, but there seems no way to do this
> in WSPR.
>
> At least I now know why I, and presumably others, have problems.
>
> 73 Dave G3YMC
>
> http://www.davesergeant.com
>
>
>



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