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Author Topic: No DRM around? Roll your own!  (Read 534 times)

Offline ThaDood

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No DRM around? Roll your own!
« on: August 14, 2018, 1538 UTC »
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.
« Last Edit: September 03, 2018, 1542 UTC by ThaDood »
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Offline Josh

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Re: No DMR around? Roll your own!
« Reply #1 on: August 14, 2018, 1634 UTC »
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.

Offline ThaDood

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Re: No DRM around? Roll your own!
« Reply #2 on: August 16, 2018, 0335 UTC »
Maybe this site might explain things about various DRM,            http://www.drm.org/what-is-drm/
« Last Edit: September 03, 2018, 1542 UTC by ThaDood »
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Offline Tim Bucknall

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Re: No DMR around? Roll your own!
« Reply #3 on: September 01, 2018, 1806 UTC »
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 :-)

Offline Stretchyman

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Re: No DMR around? Roll your own!
« Reply #4 on: September 02, 2018, 0720 UTC »
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.
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Offline JimIO

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Re: No DMR around? Roll your own!
« Reply #5 on: September 02, 2018, 1339 UTC »
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?


Offline Brian

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Re: No DMR around? Roll your own!
« Reply #6 on: September 02, 2018, 1447 UTC »
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..........

Offline Stretchyman

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Re: No DMR around? Roll your own!
« Reply #7 on: September 03, 2018, 0734 UTC »
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
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Offline redhat

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Re: No DMR around? Roll your own!
« Reply #8 on: October 09, 2018, 0906 UTC »
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
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Offline ChrisSmolinski

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Re: No DRM around? Roll your own!
« Reply #9 on: October 09, 2018, 1228 UTC »
I do not understand why someone would want to transmit DRM.

I don't even understand why someone would want to listen to DRM.  8)
Chris Smolinski
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Offline Brian

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Re: No DMR around? Roll your own!
« Reply #10 on: October 10, 2018, 2023 UTC »
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.

Offline Chris Lobdell

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Re: No DRM around? Roll your own!
« Reply #11 on: October 13, 2018, 2247 UTC »
I agree with Chris S., DRM on SW is a complete and utter waste.
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Offline redhat

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Re: No DRM around? Roll your own!
« Reply #12 on: October 14, 2018, 0220 UTC »
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
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Offline R4002

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Re: No DRM around? Roll your own!
« Reply #13 on: October 15, 2018, 1532 UTC »
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. 
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Offline ChrisSmolinski

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Re: No DRM around? Roll your own!
« Reply #14 on: October 15, 2018, 1607 UTC »
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.
Chris Smolinski
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