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LF: Re: Demodulator program for the W & G Pegelmesse

To: [email protected]
Subject: LF: Re: Demodulator program for the W & G Pegelmesse
From: "Matti Niemela" <[email protected]>
Date: Wed, 13 Mar 2002 20:18:18 +0200
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Thank You Alberto for nice PHD Radio-program. It works great with my R&S
SPM19 level meter. The sound quality is surprising good. The one second
delay is not a problem.

73 de Matti/OH2ZT
----- Original Message -----
From: "Alberto di Bene" <[email protected]>
To: "LF Mailing List" <[email protected]>
Sent: Wednesday, March 13, 2002 3:59 PM
Subject: LF: Demodulator program for the W & G Pegelmesse

Many LF enthusiasts have a Selective Level Meter, generally
made by Wandel & Golterman. Some of these units have a
demodulated output, others don't, instead providing a last
IF output at 10 kHz on the rear panel.

For this last kind of equipment I have written a sort of last IF
stage in software, which accepts as input a frequency between
40 and 20000 Hz, and extracts the AM, USB or LSB modulation
it may have, playing it through the PC sound card.

The program sports also a graphical Phase Meter, which works
only when AM is selected, and measures the incoming carrier
phase referred to the program 'BFO' phase. It can be used for
a very superfine tuning. A frequency difference of 1 Hz between
the incoming signal and the BFO produces a whole revolution
every second, so frequency differences of 10 mHz are easily

The program does not touch the audio mixer, so it's up to the user
to set it correctly. Basically you have to set the Recording panel
so that only Line In is selected, and the Playback panel so that
only Wave is selected. Make sure that Line In is *deselected*
for Playback.
Of course you will have to connect the 10 kHz output of your
Selective Level Meter to the Line In of the sound card.

The program has a very serious problem, as the played audio lags
the input by almost a second, so tuning is quite difficult.
This is due to the processing of the signal, and to the MME system
of Windows. There are ways to improve this, and maybe I will
pursue this, depending on my spare time and the acceptance
of the program.

Bear in mind that this is just a first cut, more an alpha version than
a beta, so do not have excessive expectations.... I wrote it more
as an exercise, using some routines I had already written for
the version 0.93 of Jason (to be released).
Of course any criticism, suggestions, bug reports are welcome.

The program can be downloaded from :

73  Alberto  I2PHD

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