Message-ID: <47ADFB8F.5050001@telia.com>
Date: Sat, 09 Feb 2008 20:14:23 +0100
From: "Johan H. Bodin" <jh.bodin@telia.com>
User-Agent: Thunderbird 2.0.0.9 (Windows/20071031)
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <001501c8690d$0e706f40$410d7ad5@w4o8m9> <001501c869db$a296b840$97188351@w4o8m9> <000d01c86aa8$96510040$ae197ad5@w4o8m9>
In-Reply-To: <000d01c86aa8$96510040$ae197ad5@w4o8m9>
Subject: Re: LF: Re: M0BMU WOLF Beacon
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


Dear Jim, LF group,

yes, all Wolf GUI settings were left at "factory default" except the
speed which was changed to Wolf 20. Your signal was strong, clearly
visible in the waterfall (well, with some imagination...) but I was
really surprised to see correct "print" already on line 1! I had
expected to go through a lot of tweaking and calibration before getting
any copy at all, if any...

I played a little with Stewart's command line version a few years ago -
DL4YHF's real-time Wolf GUI is really a giant step forward in "user
friendlyness" :-)

Your guess about sampling rate is absolutely correct. There is only one
clock involved - the 80MHz (TC?)XO in the receiver hardware (the ADC
clock). Perseus output sampling rate is fixed at 31250Hz (in the current
beta release). This sampling rate is re-sampled to a "standard" rate by
Windows when listening through the soundcard, and by the VAC software
(Virtual Audio Cable) when routing the signal to other programs such as
Wolf. Unfortunately, the VAC software seems to use a quite sloppy
algorithm for resampling, probably to reduce the CPU load. At some
output sampling rates, there are distorsion products that look like some
kind of "in-band aliasing" and these are not more than 40dB down or so
:-( Maybe this percent of THD goes unnoticed by "normal" VAC users who
listen to mainsream music (which is usually 100% distorsion anyway ;-) )

Hopefully, a future release of the Perseus software itself will include 
a good "VAC mechanism" and appear as a "Recording Device" with
selectable standard sampling rates in the Windows Control Panel...


Thanks for the signal!

73
Johan SM6LKM

----

James Moritz wrote:
> Thanks to SM6LKM for the reception report - the usual problem people have
> receiving WOLF is getting the correct calibration of audio sample rate and
> receiver frequency offset set up. But  I was interested to see Johan has
> used nominal settings, and it looks like these are just right. I guess if
> you are using an SDR system with a "virtual" sound card feeding data to the
> WOLF decoder, the sampling clock in the SDR defines both the receive
> frequency and the "audio" sample rate. So in this case there will only be
> one unknown requiring calibration , which could be done using any convenient
> carrier, making life much simpler.