FM Band - More Stations (using existing [approved?] tech)

[kfbkfb]

My idea is to use only the HD Radio "digital" carriers (no analog FM, no full bandwidth HD Radio)

The spectrum between +/-75kHz would be empty, thus, no analog FM to interfere with nearby FM stations or in another radio market.

It seems to me that using just the HD Radio carriers would allow more stations (HD Radio subchannels) without expanding the FM band or using yet another modulation method requiring new radios.


Kirk Bayne

 

[TheBigA]

My idea is to use only the HD Radio "digital" carriers (no analog FM, no full bandwidth HD Radio)

The HD carriers don't exist without the main signal. That was the idea trademarked by iBiquity 20 years ago.

 

[kfbkfb]

With approval, is there any technical reason why the HD Radio carriers can't be transmitted without the analog FM (thus [probably] avoiding interference with other FMs, which prevents completely filling the FM band)?


Kirk Bayne

 

[davideduardo]

The HD carriers don't exist without the main signal. That was the idea trademarked by iBiquity 20 years ago.

AM can go pure digital, as the current "permanent test" in Fredrick, MD, has shown. However, there is no current provision for an all-digital FM system.

Unlike DAB or DRM, the digital AM and FM systems in the US were designed to be backwards compatible with analog AM and/or FM.

 

[TheBigA]

AM can go pure digital, as the current "permanent test" in Fredrick, MD, has shown.

That's not using the HD system, which was in the OP. However you can hear an all digital AM signal on an HD receiver.

With approval, is there any technical reason why the HD Radio carriers can't be transmitted without the analog FM (thus [probably] avoiding interference with other FMs, which prevents completely filling the FM band)?

The FM carrier is the one that's licensed. The power and the signal are based on that.

 

[Kent]

My idea is to use only the HD Radio "digital" carriers (no analog FM, no full bandwidth HD Radio)

The spectrum between +/-75kHz would be empty, thus, no analog FM to interfere with nearby FM stations or in another radio market.

It seems to me that using just the HD Radio carriers would allow more stations (HD Radio subchannels) without expanding the FM band or using yet another modulation method requiring new radios.

Granted, my information is about 15 years old, but I was told that would be possible, at least from an engineering standpoint. An engineer said he was 95% confident you could get between six and ten channels on an HD signal with no analog signal taking up space. Sound quality, however, wasn’t included in his calculation. So, you probably couldn’t get 10 music channels on one signal, but you might be able to get that many talk stations.

The bigger challenges for a venture like that, however, are logistical. HD Radio has been around roughly 20 years, and it still isn’t widely consumed by the public. There's also the issue of HD Radio being a proprietary service and the royalties involved in running it. Converting en masse to all digital would render a ton of devices obsolete, and the public isn’t exactly clamoring to buy radio equipment. Radio's biggest strength is that it comes basically free with other products consumers want.

Something else to keep in mind is that the Eureka 147 system used in Europe would also work on FM if we didn't have analog signals. I'm not familiar enough with that technology to know about how it works in the real world, though I don’t believe an HD Radio receiver will decode it. So, we're highly unlikely to see that system adapted in any reasonable timeframe.

 

[davideduardo]

With approval, is there any technical reason why the HD Radio carriers can't be transmitted without the analog FM (thus [probably] avoiding interference with other FMs, which prevents completely filling the FM band)?

The question is "why?" There is no significant reason to eliminate analog FM, which would make almost all home and portable radios obsolete and similarly make well over half of all car radios useless. And the improvement of HD / digital over FM analog is not significant to most people, a fact which would create a lot of "I don't need that" reactions.

 

[TheBigA]

I was told that would be possible, at least from an engineering standpoint. An engineer said he was 95% confident you could get between six and ten channels on an HD signal with no analog signal taking up space.

How would it be licensed? Everything in HD is based on the main carrier.

 

[PTBoardOp94]

The HD carriers don't exist without the main signal. That was the idea trademarked by iBiquity 20 years ago.

There is provision in the HD Radio standard for full digital operation on FM.
I do not think the FCC has authorized that mode of operation, but they could do so at their pleasure.

 

[kfbkfb]

My idea is only about adding signals in the FM band (not analog FM signals, just HD Radio carriers in FM slots not usable for analog FM due to channel spacing or analog FM in nearby markets).

Since HD Radios are already for sale, no new radios would need to be developed, perhaps just FCC approval to transmit HD Radio "digital" carriers only (note: this is not the all digital HD Radio mode for the FM band).

My main idea is to add more signals to the existing FM band using existing tech in such a way as to not cause any (or very little) interference with the existing analog FM signals.


Kirk Bayne

 

[davideduardo]

That's not using the HD system, which was in the OP. However you can hear an all digital signal on an HD receiver.

The iBiquity system is an HD system. But it is not DAB such as used in much of Europe and a few other places.

HD radio in the US consists of a digital signal that shares the bandwidth with the traditional analog signal.

The FM carrier is the one that's licensed. The power and the signal is based on that.

Acctually, the allocation is for a frequency. The current FM authorizations are for either all analog or analog and digital. But there is no reason why, should there be demand and should the FCC find all digital to be in public interest that stations could not convert to pure digital.

 

[kfbkfb]

My idea leaves existing analog FM untouched, just using the HD radio carriers only (again, this is not the all digital HD Radio FM band mode) to sandwich more signals (not analog FM, just the HD Radio carriers, leaving +/-75kHz completely empty) into the existing FM band.

Upon further thought, FCC approval would almost certainly be need since there is no analog FM source for HD1, one thing that would need to be tested is: can existing HD Radios tune in the HD carriers without the analog FM signal existing?


Kirk Bayne

 

[kfbkfb]

My motivation is to place signals (using the existing HD Radio tech standard in a new way) in the FM band that don't interfere with existing analog FM.

FCC and/or HD Radio IP owner(s) would probably have to approve this use of the HD Radio carriers.


Kirk Bayne

 

[PTBoardOp94]

My idea leaves existing analog FM untouched, just using the HD radio carriers only (again, this is not the all digital HD Radio FM band mode) to sandwich more signals (not analog FM, just the HD Radio carriers, leaving +/-75kHz completely empty) into the existing FM band.

You're going to have to explain how the two bolded phrases are not contradictory before anyone can make a sensible reply.

 

[kfbkfb]

My idea is to add new signals [in this case, the HD Radio digital carriers only, but configured as though there was an analog FM signal too, which there wouldn't be] in the FM band in such a way as to use currently unusable FM channels/slots and keep interference to a minimum.

(I think I'll make a simple sketch [with the old school paper and pencil] and scan it to try to better explain what I'm thinking about)


Kirk Bayne

 

[TheBigA]

My idea is to add new signals [in this case, the HD Radio digital carriers only, but configured as though there was an analog FM signal too, which there wouldn't be] in the FM band in such a way as to use currently unusable FM channels/slots and keep interference to a minimum.

In most populated areas, there's no room in the FM band for any more signals. All the empty space has been taken for translators or LPFM.

 

[Red Plume]

"MA3" is the standard for all-digital on the AM band, and "MP3" is the already developed standard for all-digital on the FM band.

"MP3" is unfortunately named and should not be confused with MPEG1 Layer 3, which is a commonly used audio file format.

Edit: Reworded due to a misunderstanding on my part.

 

[Red Plume]

The spectrum between +/-75kHz would be empty, thus, no analog FM to interfere with nearby FM stations or in another radio market.

I can't see it working in the exact way you're suggesting, but a variation that might work would be an all digital MP3-HD that could fit on a second adjacent where an analog signal would not fit.

 

[kfbkfb]

Here's my (potentially award winning [obviously pen and paper wo/liquid paper corrector]) sketch of what I mean (using some KC area stations as examples):

I get a weak signal on 94.5, hence the ?, AFAIK, 94.3 and 94.7 can't be used at all in the KC area.

The HD Radio digital carriers are transmitted at a lower level than analog FM, but testing would need to be done to see if HD Radio digital carriers alone in a sequential FM channel would cause much interference.


Kirk Bayne

 

[Red Plume]

Here's my (potentially award winning [obviously pen and paper wo/liquid paper corrector]) sketch of what I mean (using some KC area stations as examples)

Thanks for including the illustration.

I think the big problem here would be that HD signals on the first adjacents would take away the right of the analog station to upgrade to HD in the future.

I don't think there's an advantage to using IBOC-without-analog over a full channel "M-P-3" HD signal in your example.