No DRM around? Roll your own!

[ThaDood]

I was looking at this European company for their AM C-QUAM TX's, but found a neat DRM milliwatt transmitter,  http://www.aspisys.com/drmax.htm  So, if we don't have DRM here yet, we can literally roll our own Part #15-wise.

[Josh]

Is there a redundant mode to dmr? As I recal dmr is based on STANAG4285, wich in its usually found emission on hf is not in the mode best suited for error free or weak signal decoding. The 75Bd S4285 mode is incredibly hardy though, but doesn't lend itself to voice transmission due the low bitrate.

[ThaDood]

Maybe this site might explain things about various DRM,            http://www.drm.org/what-is-drm/

[Tim Bucknall]

from my experience with enforcement in the UK, the inspectors would not even be able to tell a drm signal from background noise so you could pretty much do what you want :-)


however its the am stereo tx that gets me excited , thanks for the link :-)

[Stretchyman]

I'm confused at what they offer as encoding is done externally? So it's just an amp?

Can anybody enlighten me with any schematics?

Str.

[JimIO]

Same way you generate SSB with a sound card because DRM is SSB.
Search for "sound card ssb modulator" or "i and q phasing modulator".
You gonna build one?

[Brian]

I'm confused at what they offer as encoding is done externally? So it's just an amp?

Can anybody enlighten me with any schematics?

Str.

It's basically just an AM transmitter modified to take a 2nd audio input.

I altered a transmitter to do this years ago and used the DREAM software to generate the DRM with some success.

Nobody except me was able to hear it though..........

[Stretchyman]

Looks like I already have if it's a standard A.M. Tx with another audio I/P.

I suspect however for SSB it has to be a 'Linear' amp and I use Class E Generators so not suitable.

Plenty of Linears out there so no need for me to intervene!

Str

[redhat]

I'm confused at what they offer as encoding is done externally? So it's just an amp?

Can anybody enlighten me with any schematics?

Str.

It's basically just an AM transmitter modified to take a 2nd audio input.

I altered a transmitter to do this years ago and used the DREAM software to generate the DRM with some success.

Nobody except me was able to hear it though..........

Actually it requires I and Q modulators to produce the DRM waveform at RF frequencies.  That is the easy part, generating the DRM baseband in the first place is where the money is.  You want stereo?  Prepare to pay Dolby(or Fraunhofer) $2K for a license to use their encoder.

Not worth it, unless you have a 3KW peak capable transmitter to get 300W RMS out of it, and are interested in NVIS only.  I too tried it a few years back, only got one report.

+-RH

[ChrisSmolinski]

I do not understand why someone would want to transmit DRM.

I don't even understand why someone would want to listen to DRM. 

[Brian]

I'm confused at what they offer as encoding is done externally? So it's just an amp?

Can anybody enlighten me with any schematics?

Str.

It's basically just an AM transmitter modified to take a 2nd audio input.

I altered a transmitter to do this years ago and used the DREAM software to generate the DRM with some success.

Nobody except me was able to hear it though..........

Actually it requires I and Q modulators to produce the DRM waveform at RF frequencies.  That is the easy part, generating the DRM baseband in the first place is where the money is.  You want stereo?  Prepare to pay Dolby(or Fraunhofer) $2K for a license to use their encoder.

Not worth it, unless you have a 3KW peak capable transmitter to get 300W RMS out of it, and are interested in NVIS only.  I too tried it a few years back, only got one report.

+-RH

I know that but the TX needed to be modified to take that modulation.

I was only testing it on MW.  No reports and I wasn't looking for any either.

[ChrisLobdel]

I agree with Chris S., DRM on SW is a complete and utter waste.

[redhat]

I agree with Chris S., DRM on SW is a complete and utter waste.

I think the intention was good; make SW more listenable and add interactive multimedia.  The reality is it just doesn't work all that well without a lot of effort on the part of the listener, efforts that would make analog better too.

+-RH

[R4002]

I agree with Chris S., DRM on SW is a complete and utter waste.

I think the intention was good; make SW more listenable and add interactive multimedia.  The reality is it just doesn't work all that well without a lot of effort on the part of the listener, efforts that would make analog better too.

+-RH

Indeed.  My higher-end portable Chinese-made shortwave radio doesn't even have support for it....makes me wonder how the parts of the world with higher amounts of SW listenership (a lot of which is done with much cheaper radios) plan on implementing DRM broadcasting and shutting down analog when most of their listeners are using lower-end shortwave radios that receive AM mode only. 

[ChrisSmolinski]

Indeed.  My higher-end portable Chinese-made shortwave radio doesn't even have support for it....makes me wonder how the parts of the world with higher amounts of SW listenership (a lot of which is done with much cheaper radios) plan on implementing DRM broadcasting and shutting down analog when most of their listeners are using lower-end shortwave radios that receive AM mode only.

In general, if you have a strong enough signal for DRM, you have an excellent signal for analog. And if you have a weaker signal, you have enough for analog, and not enough for DRM, so you get nothing. DRM seems to be a solution in search of a problem.