Message-ID: <3C6BADA9.B0B8CF6D@usa.net>
Date: Thu, 14 Feb 2002 13:29:29 +0100
From: "Alberto di Bene" <dibene@usa.net>
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To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: HELL Tests on 137.400 kHz
References: <200202140546_MC3-F1F2-D9F6@compuserve.com>
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"Holger 'Geri' Kinzel, DK8KW" wrote:

>> I am preparing a Web page that will show a perfect copy of a Jason
>> signal,, while that very same signal is practically undetectable with Argo.

>... that is some interesting information, and I will definetely run more
> tests in Jason soon to get a better feeling for it's capabilities.

Well, it seems that I spoke too soon.......
During the lunch interval I discovered that I have been baffled by the
AC97 standard again....
What happened is that I started at the same time both Jason and Argo,
while Winamp played a WAV file obtained by mixing a Jason signal
with a measured amount of white noise (43 dB stronger than the
Jason signal), using Cool Edit  (TNX to Stewart Nelson for this tip).

Jason did a perfect decoding having been set with a center frequency
of 800 Hz.  Argo did not show anything at this frequency.
However I have just discovered, by chance, that the signal is visible
on Argo around 825 Hz.........
Jason samples at 11025 Hz, while Argo uses 5512.
The AC97 driver of the sound chip on my laptop performs the
downsampling needed to accommodate the requests by both programs
at the same time. Apparently the correctness of this downsampling
process leaves much to be desired.... a lesson for the future.

So the bottom line is that, at least for the present test, what is
decoded by Jason is also visible on Argo. Sorry for having
misled you. But the tests will continue.

73  Alberto  I2PHD