Receiving DRM with the DX-394
 

The DX-394 can be readily adapted to have a 3rd IF at 12kHz to feed a
computer sound card with which free software can decode DRM transmissions.
Jan Terpstra has designed a two transistor 455kHz-to-12kHz "quick and dirty"
converter that he and I have built. Today I successfully received DRM
transmissions from Sackville using the DX-394 with the converter and the
free DReaM software running on a Celeron 450MHz computer.

The DReaM software is intriguing in its own right and is capable of doing AM
and SSB demodulation from the 12kHz IF using DSP. Remarkably, I think it
excels the stock AM demodulator at very weak signal reception and provides
selectable bandwidth in 1kHz steps from 1 to 15 kHz.

For more on DRM on the DX-394 visit/join
http://groups.yahoo.com/group/RADIOSHACKDX394/ .

Tom

"-=jd=-" wrote in
:

On Wed 23 Jun 2004 07:20:04p, "Tom Holden"
wrote in message :

The DX-394 can be readily adapted to have a 3rd IF at 12kHz to feed a
computer sound card with which free software can decode DRM
transmissions. Jan Terpstra has designed a two transistor
455kHz-to-12kHz "quick and dirty" converter that he and I have built.
Today I successfully received DRM transmissions from Sackville using
the DX-394 with the converter and the free DReaM software running on a
Celeron 450MHz computer.

The DReaM software is intriguing in its own right and is capable of
doing AM and SSB demodulation from the 12kHz IF using DSP. Remarkably,
I think it excels the stock AM demodulator at very weak signal
reception and provides selectable bandwidth in 1kHz steps from 1 to 15
kHz.

For more on DRM on the DX-394 visit/join
http://groups.yahoo.com/group/RADIOSHACKDX394/ .

Tom



I have two of these and have started scrounging :) In the mean time my
PCR-1000 may also be useful ;)


With an unmodified ICOM PCR-1000 radio and the Dream software, I was
able to decode the RNW broadcast out of Bonaire on LSB by tuning up
about 5k, purely by accident. I also had to "reverse" the signal (a
config setting within the Dream software).

I was actually to the point where I thought it wouldn't work and had
left the Dream software running while I tuned around a bit just to get a
better feel for the sound of the raw stream...

Now, It did not decode it flawlessly - it would only decode about 5 to
10 seconds before dropping out for a bit. But the audio I heard was
comparable to listening to NPR on a local FM station.

There's a kit I could get for about $25USD that would modify the 1st IF
to 12kHz (I think that's what it was), but I don't want to mod my
receiver.

In any event, the bits I was able to hear sounded great.

-=jd=-



Interesting !!!!! Just downloaded the Dream software and have begun
playing with it :) The Drm station I can hear at the moment are not very
stron, but managed to get a snippet of things to come I hope !!!. You
might also try using th packet output from you PCR. I seem to be able to
get partial recognition of the signal from eithe port on the RX. Would ne
nice if the software supported the RX though to make at least inital
tuning from station view work :)

--
Panzer

"Tom Holden" wrote in message
. ..
AM demodulator at very weak signal reception and provides
selectable bandwidth in 1kHz steps from 1 to 15 kHz.
Tom

Tom, how are you adjusting the bandwidth in 1kHz steps with the software?

Thanks.

Al KA5JGV
San Antonio, Tx.

Hello there!

Does anyone know if there is any service targeting Africa, the mid
africa. I have a Sony ICF 7600D .... I've that modification manual for
DRM. Can I receive DRM from here?

Thanks in advance.

Raqueeb Hassan
Congo (DRC)

----- Original Message -----
From: "Al - KA5JGV"
Tom, how are you adjusting the bandwidth in 1kHz steps with the software?

The software does more than DRM. The bandwidth selection is in AM mode not
DRM.

In the AM mode, the Evaluation page of the DReaM software has 15
radiobuttons to select bandwidth. Under the spectral display, a red bar
shows the bandwidth selected relative to the demodulator centre frequency,
which you set by clicking on the display. For example, if you have tuned the
radio toan AM station so that the carrier is at 12 kHz, you see a spike in
the display at that frequency. Clicking on the spike centres the DSP filter
on it. Then you can vary the filter bandwidth. It's all done in the math in
the software.

You can also select USB or LSB, thus shifting the filter to one side of the
carrier. Works great on AM with carrier to suppress interference that's one
sided. Just think of it as a 3rd IF with variable bandwidth and passband
tuning with an AM demod and a product detector - yes you can demodulate
suppressed carrier AM too.

73, Tom

"Raqueeb Hassan" wrote in message
Does anyone know if there is any service targeting Africa, the mid
africa. I have a Sony ICF 7600D .... I've that modification manual for
DRM. Can I receive DRM from here?

A schedule of DRM transmissions is published at
http://www.drm.org/livebroadcast/globfieldtrial.htm . While none appear to
target central Africa, it may be possible to receive others. With your
unmodified radio, tune to the frequencies scheduled and listen for a hash
noise louder than that 10kHz away to either side. If you hear it and it
moves the S-meter a couple of units higher than either side, you will have a
good chance of decoding it.

Regards,
Tom

"Tom Holden" wrote in message
...
The software does more than DRM. The bandwidth selection is in AM mode not
73, Tom

Tom, thanks for the detailed information. I have used this program many
times for DRM and never realized there was an AM option to it. You're right,
it's quite impressive what all can be done with this mode. I have a Ten-Tex
RX-350 so all the DSP options are already there, but for a radio without
these features, this program is great. All interested in DRM or DSP that
have a 12kHz IF should try it.

Al KA5JGV