K3: DRM listening?

[K1LI]

Now that I'm enjoying SWLing again, I'd like to try to "decode" Digital
Radio Mondiale. Has anyone succeeded in doing this without buying a
purpose-built DRM receiver?

--
73 -- Brian -- K1LI
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[ab2tc]

Hi,

Yes, I have been using the K3, LP-Pan, PowerSDR, Virtual Audio Cable and a free decoder program called Dream. It was quite a while ago and the experience wasn't that great. The slightest fade and the decoder would lose the signal. Also, there are precious few DRM transmitters that can be heard in North America. The future of DRM is pretty murky. As you can guess from my description, it's also quite a few programs that all have to be set up correctly, none of them being really simple.

AB2TC - Knut

Brian Machesney wrote

Now that I'm enjoying SWLing again, I'd like to try to "decode" Digital
Radio Mondiale. Has anyone succeeded in doing this without buying a
purpose-built DRM receiver?

--
73 -- Brian -- K1LI
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[Jim Brown-10]

On Fri, 11 Dec 2009 12:25:40 -0800 (PST), ab2tc wrote:

> As you can guess from
>my description, it's also quite a few programs that all have to be set up
>correctly, none of them being really simple.

Some of the programs you mention would appear to be un-necessary. If the DRM
decoder will work with detected analog audio, all should be needed is a feed
from the K3 line output to the computer sound card. That requires nothing more
than a simple 2-wire cable. Or is there more that I'm missing?

73,

Jim K9YC



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[ab2tc]

I am not sure if the 13kHz FM filter is wide enough, but if it is, your suggestion should work. I didn't have the FM filter at the time. I think PowerSDR allows 15kHz for its DRM mode and it may have less group delay distortion than the crystal filter. The decoder is finicky.

Knut - AB2TC

Jim Brown-10 wrote

On Fri, 11 Dec 2009 12:25:40 -0800 (PST), ab2tc wrote:

> As you can guess from
>my description, it's also quite a few programs that all have to be set up
>correctly, none of them being really simple.

Some of the programs you mention would appear to be un-necessary. If the DRM
decoder will work with detected analog audio, all should be needed is a feed
from the K3 line output to the computer sound card. That requires nothing more
than a simple 2-wire cable. Or is there more that I'm missing?

73,

Jim K9YC

<snip>

[KK7P]

In general, DRM decoders expect a receiver IF of 12 kHz and a bandwidth
of up to 20 kHz.  The K3 can provide neither without modification.

Some DRM modes are narrower and can be accommodated if the FM roofing
filter (nominal 13 kHz) is installed.  But getting the IF output to the
DRM decoder still requires modifications to the K3.

Some DRM decoders are free, others require a licensing fee.

WinDRM is different, being a mode designed for Amateur radio use,
primarily for digital voice but also for file transfer.

73,

Lyle KK7P
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[P.B. Christensen]

> Some DRM modes are narrower and can be accommodated if the FM roofing
> filter (nominal 13 kHz) is installed.  But getting the IF output to the
> DRM decoder still requires modifications to the K3.

DRM decoding with the K3 is easy with the SDR-IQ together with SpectraVue,
VAC and DReaM software.  I set SpectraVue to an 11 kHz passband, engage VAC
and start listening to DRM.   Been using it that way for the past several
months with excellent results.

Paul, W9AC

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[David Pratt]

Could the 8.215MHz output from the IF OUT jack be fed to a simple mixer
with a 8.203 or 8.227MHz crystal to provide a 12kHz i.f.?

I have used this method very successfully on the Sangean ATS-803A and
Lowe HF-225 receivers with both DReaM v.1.6.1cvs and DRM Software Radio
v2.0.38 programs.  But this was by converting the 455kHz i.f. to 12kHz.

David G3DMP

In a recent message, Lyle Johnson <[hidden email]> writes

>
>In general, DRM decoders expect a receiver IF of 12 kHz and a bandwidth
>of up to 20 kHz.  The K3 can provide neither without modification.
>
>Some DRM modes are narrower and can be accommodated if the FM roofing
>filter (nominal 13 kHz) is installed.  But getting the IF output to the
>DRM decoder still requires modifications to the K3.
>
>Some DRM decoders are free, others require a licensing fee.
>
>WinDRM is different, being a mode designed for Amateur radio use,
>primarily for digital voice but also for file transfer.

--
David G4DMP
Leeds, England, UK



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[Jim Brown-10]

On Fri, 11 Dec 2009 13:07:31 -0800, Lyle Johnson wrote:

>In general, DRM decoders expect a receiver IF of 12 kHz and a bandwidth
>of up to 20 kHz.  The K3 can provide neither without modification.

I'm confused. What "20 kHz bandwidth" are we talking about? The output of the
detector?  Are you saying that the IF in a DRM-compatible RX has a center
frequency of 12kHz, and that the detector has to look at that 12 kHz IF?  

>Some DRM modes are narrower and can be accommodated if the FM roofing
>filter (nominal 13 kHz) is installed.  But getting the IF output to the
>DRM decoder still requires modifications to the K3.

Like what?

73,

Jim K9YC





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