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Dream DRM software "receiver"

Posted: Sun Feb 22, 2009 5:52 am
by K9EZ

Re: Dream DRM software "receiver"

Posted: Mon Nov 09, 2009 8:14 am
by Kelly
Interesting! Thanks for the link Kent.

So does anyone have any thoughts or inside skinny on why the US has pretty much disregarded the potential use of DRM on the Medium Wave band? I've seen demos of DRM at the NAB a couple years ago and was pretty impressed. Other than the inability to allow for a hybrid digital/analog approach, the modulation scheme seems like a reasonable transitionary move for the AM band by allowing broadcasters to use the X-Band for 1kW ND DRM transmissions within a market, simulcasting their analog channel.

Someone told me once that in order to get something like that in front of the Commission, it would have to be driven by either Broadcasters, or private industry.

Re: Dream DRM software "receiver"

Posted: Fri Nov 13, 2009 6:15 pm
by RFWarrior
DRM has all the same issues IBOC has - the only difference is a bit more flexibility in bandwidth and injection ratios (I.e., SSB injection). DRM was tested in a hybrid mode and when they saw signs of the same problems that IBOC is having now, they opted not to pursue it further, so it's only offered in digital only mode - no broadcaster would take that on without a whole lot more receivers out there than currently exist in the US market, although as others have noted, it could be provided as an option for new licensees. Note also that DRM on MW in Europe is run at much higher power levels. IBOC is run at 28 dB below the analog carrier. So it's not really a fair comparison coverage wise. I have a DRM AM transmitter in Eastern England that can be received in Geneva, Switzerland - but it's pumping out about 80kW of digital signal.... that's a lot of potential "hash" :)

Best,

Jeff

Re: Dream DRM software "receiver"

Posted: Fri Nov 13, 2009 7:20 pm
by Deep Thought
a lot of potential "hash"

Actually, probably not. The occupied bandwidth in pure digital mode shouldn't be much more than the analog bandwidth would be. What gets me is all this nattering on about extending the FM band to 76 MHz fails to take into account the need for all new FM radios here in the US while an obvious digital fix is to run those 'failed' AMs we hear so much about in full digital mode at full power, but new receivers for that is considered a deal-breaker. If iBiquity wasn't so preoccupied with ripping off broadcasters and instead put money toward subsidized receivers there could be a whole new service born from and coexisting in the Ancient Modulation band.

Re: Dream DRM software "receiver"

Posted: Tue May 14, 2013 9:50 am
by GoobeNet
To bring back a dead thread, i just decided to try this on my FM... as a subcarrier. So far, so good.

Using Dream DRM as the encoder (run the app with a -t flag for transmit), set the offset to 67,000hz and voila! I have a DRM-based subcarrier being generated by a PC right into the SCA input on my 8400.

Goodbye IBOC.

Almost so simple to think nobody's tried doing this before.

Re: Dream DRM software "receiver"

Posted: Tue May 14, 2013 11:41 am
by Deep Thought
GoobeNet wrote:Almost so simple to think nobody's tried doing this before.
:mrgreen:

Re: Dream DRM software "receiver"

Posted: Tue May 21, 2013 7:25 am
by amguy
Deep Thought wrote:a lot of potential "hash"

Actually, probably not. The occupied bandwidth in pure digital mode shouldn't be much more than the analog bandwidth would be. What gets me is all this nattering on about extending the FM band to 76 MHz fails to take into account the need for all new FM radios here in the US while an obvious digital fix is to run those 'failed' AMs we hear so much about in full digital mode at full power, but new receivers for that is considered a deal-breaker. If iBiquity wasn't so preoccupied with ripping off broadcasters and instead put money toward subsidized receivers there could be a whole new service born from and coexisting in the Ancient Modulation band.
As a small am station owner..would be willing to try the full digital mode..but I also totally agree with Deep that if iBiquity would put money toward subsidized receivers it might make us small guys consider this! Since I'm not the smartest guy(I bought a stand alone AM..proves the statement right?), in full digital mode either in DRM or IBOC would that still require low power at night because of skywave? And why hasn't the FCC looked at the DRM?

Re: Dream DRM software "receiver"

Posted: Tue May 21, 2013 9:41 am
by GoobeNet
Why the FCC hasn't looked at DRM? Simple answer, money. iBq was the only folks who provided the FCC with a "hybrid" solution. When i talked to the DRM folks down at NAB, they said it'd "never work in the US due to the frequencies being incompatible"... When i told them that we can just shove it in anywhere they kinda looked at me like i shot their dog thinking "oh, crap, why didn't we think of that!".

Re: Dream DRM software "receiver"

Posted: Tue May 21, 2013 12:59 pm
by Deep Thought
amguy wrote: in full digital mode either in DRM or IBOC would that still require low power at night because of skywave?
Modulation scheme doesn't change the propagation physics on MW so yes, you'd still have to protect other stations (and vice versa) even with digital. The protection ratios might possibly be loosened up some (right now it's 1:20 co-channel) but unless *everyone* goes digital at once there is no way to do that. However, the coverage you would have should be interference-free out to where the radio loses lock.

But it'll never happen anyway...it would require a massive program to replace 100 times as many radios as the ATSC conversion replaced TVs, and there is no cable/satellite feed for your radio if you want to keep the one you have. Chicken, meet egg. And I'll reiterate that moving AM to channels 5 and 6 is a non-starter for the exact same reason.

Re: Dream DRM software "receiver"

Posted: Wed May 22, 2013 9:22 am
by GoobeNet
I'm still looking into how the DRM synchronus mode works with AM. Apparently, much like AM stereo, it lives side-by-side in quadrature with the normal carrier. I have some software that can do it... Just gotta plug it in and find out how it really works. First i need an AM transmitter that can do I/Q and regular audio (like AM Stereo).

--
Alex

Re: Dream DRM software "receiver"

Posted: Thu Jan 02, 2014 4:25 pm
by okcradioguy
GoobeNet wrote:To bring back a dead thread, i just decided to try this on my FM... as a subcarrier. So far, so good.

Using Dream DRM as the encoder (run the app with a -t flag for transmit), set the offset to 67,000hz and voila! I have a DRM-based subcarrier being generated by a PC right into the SCA input on my 8400.

Goodbye IBOC.

Almost so simple to think nobody's tried doing this before.

So, this might be a very good option for delivering audio from point A to point B for a station, if they controlled both ends. Can ask the specifics on the hardware end, on both ends? I'm assuming you're running audio into a sound card, and out another sound card to the SCA input of your exciter? On the other end, are you using a hardware solution to decode the subcarrier, then running that tap over to the computer sound card to decode? Or are you using some SDR dongle?

Thanks in advance! This is VERY intriguing !!

Re: Dream DRM software "receiver"

Posted: Tue Feb 04, 2014 10:51 am
by ai4i
Here is the solution to using DRM on your AM station and without losing your analog listeners:
Do it with one of the many many AMs whose listeners are all listening to the station's 250w FM translators on TV towers.
The DRM transmitter, if the AM day and night signals are acceptable at the translator sites, will also double as a free STL.

Re: Dream DRM software "receiver"

Posted: Fri Feb 21, 2014 10:38 am
by GoobeNet
It's simple software through and through. I'm using a high grade soundcard to maintain tilt and frequency response (echo AudioFire12, yes, overkill, but it was what i had around).

SDR on the RX as i'm breaking spec to begin with, it's hard to even find a radio to receive DRM in native form, let alone dig it out of the SCA section. :)

When i find that elusive "free time" DeepThought and myself are going to see if i can use an old SCA radio as the RX to feed a PC for decoding, or even use a little IC in the radio itself.

--
Alex Hartman