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DRM: In Band "ON" Channel

A

audiophile.

Guest
15 kHz total (10 kHz DRM) Special "single channel simulcast" that uses 10 kHz DRM with one analog sideband.

Simulcast: 15 kHz total (10 kHz DRM): A 5 kHz spectrum saving mode, using only one sideband of the AM signal. Under development as an extension of a current product only 10 kHz wide Ð 5 AM and 5 DRM.

http://www.drm.org/broadcastmanual/summarytable2.php
 
audiophile. said:
15 kHz total (10 kHz DRM) Special "single channel simulcast" that uses 10 kHz DRM with one analog sideband.

Simulcast: 15 kHz total (10 kHz DRM): A 5 kHz spectrum saving mode, using only one sideband of the AM signal. Under development as an extension of a current product only 10 kHz wide Ð 5 AM and 5 DRM.

http://www.drm.org/broadcastmanual/summarytable2.php
Click to expand...

This site is frustratingly short on details, but the way I read it this mode is not backwards-compatible with standard analog receivers. The digital sideband would occupy the space where the other analog sideband used to be, and existing analog receivers would demodulate it, mixing a loud hiss with the audio.

Single-sideband analog receivers would be able to decode the analog just fine, and there *are* millions of such receivers out there - but they still form a very tiny fraction of the radios in use.

IMHO there is no magic bullet. You **cannot** stuff a digital signal with enough bandwidth to pass listenable audio into the same 10KHz channel as an analog signal. Either you:

  • Stuff the digital into your own channel, and interfere with yourself
  • Stuff it into adjacent channels, and interfere with whoever may be in those channels
  • Stuff it somewhere else in the spectrum
 
I was at a SBE meeting with Nautel a few years ago and they said then that DRM is not compatible with current analogue AM radio stations. That's one of the reasons other countries are starting to look at IBOC. Compatibility testing has taken place in Japan.
 
This site is frustratingly short on details, but the way I read it this mode is not backwards-compatible with standard analog receivers. The digital sideband would occupy the space where the other analog sideband used to be, and existing analog receivers would demodulate it, mixing a loud hiss with the audio.
Click to expand...

Unless it is transmitted in a way to cause amplitude cancellation, or in reduced amplitude to an acceptable noise level. If it was tranmitted on your main carrier frequency there is likely to be better spectrum protection within the channels bandpass and a less digital power might give acceptable results.

Single-sideband analog receivers would be able to decode the analog just fine, and there *are* millions of such receivers out there - but they still form a very tiny fraction of the radios in use.
Click to expand...

Not true. This is how Powerside works. The Main carrier still present - no BFO needed.

IMHO there is no magic bullet. You **cannot** stuff a digital signal with enough bandwidth to pass listenable audio into the same 10KHz channel as an analog signal. Either you:

  • Stuff the digital into your own channel, and interfere with yourself
  • Stuff it into adjacent channels, and interfere with whoever may be in those channels
  • Stuff it somewhere else in the spectrum
Click to expand...
Frankly, I don't mind the notion of interfering with yourself. At at least you hold all the cards and choose the tradeoff level that meets your specs.
 
audiophile. said:
Unless it is transmitted in a way to cause amplitude cancellation, or in reduced amplitude to an acceptable noise level. If it was tranmitted on your main carrier frequency there is likely to be better spectrum protection within the channels bandpass and a less digital power might give acceptable results.
Click to expand...

That's a thought - transmit the digital out of phase on either side of the carrier so it cancels out in the analog receiver. I suppose you drop the one analog sideband to allow one side of the digital to get through free of analog interference.

Man, you could sure have a hissy mess if the analog receiver's passband wasn't symmetrical! (or for that matter, if the transmitting antenna/tuning network/transmitter/propagation path weren't symmetrical)

Single-sideband analog receivers would be able to decode the analog just fine, and there *are* millions of such receivers out there - but they still form a very tiny fraction of the radios in use.
Click to expand...

Not true. This is how Powerside works. The Main carrier still present - no BFO needed.
Click to expand...

I was reading this as having the digital on one side of the carrier and the analog on the other -- then, the single-sideband receiver would strip the digital and pass only the analog. It could be that's not how this works. The BFO is a different issue.
 
Some 15 years ago, I sat with my neighbor who was a tech for Bell Labs. We talked out loud about different ideas to send a digital stream, simultaneous with an monaural analog program, on AM. His idea kept going back to phase modulation, using a C-Quam style stero signal. The analog would only be heard on analog, and digital noise only on digital recievers, with any noise being cancelled by the 180 phase difference.

I took the idea to my chief engineer, who's a pretty bright guy. He was fascinated by the ideas, but it kept coming back to ONE problem. There is just NOT enough bandwidth in 10kc to do BOTH. Like squeezing a basketball through a garden hose, sooner or later, it'll split and leak. It appears he was right. Ibiquity AM IBOC proves it. Leonard Kahn is right, again.

For it to work on AM, analog must cease, and the standard would have to be all digital all the time, ending, in my opinion, illegal sideband interference. It is a very big dissapointment to me. I really thought that this would work. It's a failure.
 
AMFMSW wrote: "There is just NOT enough bandwidth in 10kc to do BOTH. Like squeezing a basketball through a garden hose, sooner or later, it'll split and leak. It appears he was right. Ibiquity AM IBOC proves it. Leonard Kahn is right, again."

Do you know about Leonard Kahn's Cam-D system?

http://www.wrathofkahn.org/
 
I am familiar with Cam-D. I think Leonard kahn is a technical genius, up there with Armstrong. The problem seems to be, they both suffered from presenting their ideas successfully.

My first encounter with a Kahn product was the Voice Symetrex (am I correct in the name?). It was in a junk closet at a station in Mt. Holly NJ, along with a Gates Sta-Level. Our audio chain was using a CBS volumax/audimax pair, and sounded like crap. After replacing the rectifier in the Gates, I jumpered it into the audio chain. The difference was awsome. I then put a repaired Symetrex in the chain, and it sounded as smooth as a baby's ass. It allowed us to go to full modulation in ages without distortion. The PD asked what I did, and was astonished that the junk he was ready to throw out was a savior. I believe the Voice Symetrex was Kahn's first offering.
 
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