I think your 94.7 and 94.9 signals might overlap.
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FM Band - More Stations (using existing [approved?] tech)
- Thread starter kfbkfb
- Start date
I think your 94.7 and 94.9 signals might overlap.
IIRC, Analog FM + HD Radio still fit in an FM channel (HD Radio uses previously unused spectrum space in an FM channel), the advantage of not having a signal in the space normally taken by the analog FM signal is reducing interference with nearby signals (probably in different radio markets, but maybe also sequential stations in the same radio market).
Anyway, that's my idea for using existing tech in a new way to transmit more programs in the FM band without expanding the band or developing a new modualtion scheme (and marketing new radios to decode the new type of signal).
Kirk Bayne
Anyway, that's my idea for using existing tech in a new way to transmit more programs in the FM band without expanding the band or developing a new modualtion scheme (and marketing new radios to decode the new type of signal).
Kirk Bayne
No, they encroach on the first adjacent channels. Here's a spectrum analyzer screenshot from Wikipedia: https://en.wikipedia.org/wiki/HD_Radio#/media/File:FM_spectrum_IBOC.png
Kirk - thanks, the sketch was illustrative.
A concise way to describe your suggestion might be: keep all current licenses in analog FM, and additionally issue some new licenses which are prohibited from broadcasting in analog, but only HD Radio.
Because all incumbent licensees are permitted to use HD Radio, I don't think there would be many new stations created from this plan. The nominal HD Radio mask is +- 200 kHz from the carrier, so any HD-only station on 94.7 or 95.1 would definitely be interfered with by KCMO.
A license on 94.5 might work. It would depend on the spacing rules that would be devised for an HD-only broadcast and an incumbent analog broadcast, since you mention there is a weak signal heard on 94.5 at your location.
By the way, according to iBiquity documentation, the full-digital FM HD spectral mask is the same as the hybrid mask without the analog portion. The digital carriers are not moved. So what you have described is in fact the HD full digital modulation.
If the goal was simply to create more services in the FM band, I think requiring broadcasters use HD Radio and have at least one additional subchannel would be more impactful.
A concise way to describe your suggestion might be: keep all current licenses in analog FM, and additionally issue some new licenses which are prohibited from broadcasting in analog, but only HD Radio.
Because all incumbent licensees are permitted to use HD Radio, I don't think there would be many new stations created from this plan. The nominal HD Radio mask is +- 200 kHz from the carrier, so any HD-only station on 94.7 or 95.1 would definitely be interfered with by KCMO.
A license on 94.5 might work. It would depend on the spacing rules that would be devised for an HD-only broadcast and an incumbent analog broadcast, since you mention there is a weak signal heard on 94.5 at your location.
By the way, according to iBiquity documentation, the full-digital FM HD spectral mask is the same as the hybrid mask without the analog portion. The digital carriers are not moved. So what you have described is in fact the HD full digital modulation.
If the goal was simply to create more services in the FM band, I think requiring broadcasters use HD Radio and have at least one additional subchannel would be more impactful.
That's what I get for not checking (just assuming) FM +HD bandwidth before making my proposal 
I noticed my (old) Sony HD radio will tune in both odd and even FM frequencies so...
Maybe the HD Radio only carriers (in my sketch) could be transmitted on the even FM frequencies, such as 94.4 or 94.6 (perhaps a mandate from the FCC requiring that HD capable FM radios must tune in the even FM frequencies too).
Kirk Bayne
I noticed my (old) Sony HD radio will tune in both odd and even FM frequencies so...
Maybe the HD Radio only carriers (in my sketch) could be transmitted on the even FM frequencies, such as 94.4 or 94.6 (perhaps a mandate from the FCC requiring that HD capable FM radios must tune in the even FM frequencies too).
Kirk Bayne
It doesn't matter. After all these years virtually no one listens to the HD Radio subchannels as it is. Broadcasters have been turning them off, not clamoring to add more.
All the development in the past 10 years is with wireless 4G/5G connectivity, streaming, smart devices and apps. No one is buying radios at all, never mind HD Radios. Your next new car will probably have in-dash streaming apps font and center, FM radio buried in a sub-menu, HD Radio disabled by default and AM radio removed altogether.
I like tech just for the sake of tech, hence my moderate interest in HD Radio.
I guess the impetus now will be to develop a very low data rate (monophonic), moderate bandwidth (maybe to 10kHz or 12kHz) audio codec so that even more streamers can listen to acceptable sounding audio (at least on their smartphone speakers) on existing cell phone networks without overloading them.
Kirk Bayne
I guess the impetus now will be to develop a very low data rate (monophonic), moderate bandwidth (maybe to 10kHz or 12kHz) audio codec so that even more streamers can listen to acceptable sounding audio (at least on their smartphone speakers) on existing cell phone networks without overloading them.
Kirk Bayne
Those days are gone too. 3G has been turned off and 4G is now the entry level for data speed. Most people have unlimited data plans and are not concerned with reducing audio bandwidth. Low quality audio already sunk AM radio, today's streamers aren't going to repeat that mistake.
I'm confused. The "impetus" for whom? Who will be doing this?
Right now no one's buying cars either, so the prognostication of HD disappearing and FM being buried in a submenu somewhere is a little premature.
The cell networks won't be overloaded by users playing audio at normal bitrates, like 64-128 kbps. Audio codecs are getting more efficient so that quality shouldn't have to be compromised. Stereo is best as many smartphones/tablets/PCs have stereo speakers. Streaming shouldn't just sound acceptable, it should be at least as good as the best quality FM radio sound.
The biggest sinker of AM radio wasn't the audio quality but that metro areas outgrew the stations' coverage as cities grew and suburbs became the places to move. That was a problem at least as far back as the mid-70's, when AM was still at least half of all radio listening and FM was an extra add on in new cars.
AM audio quality is a bigger problem now because of all the electronics in cars.
Streaming audio quality is already quite good and getting better everyday. The biggest problem for streaming is that it's dependent on multiple other technologies. I've yet to find an internet provider that can meet its service uptime promise. Bluetooth also has a loss rate that's definitely noticeable compared to wired devices. I don't know how long working out those problems will take, though one could reasonably argue that today's music consumer doesn't care much. If the average listener cares, (s)he would seem to value the convenience over the quality. After all, you don't see portable CD players anymore.
It could work but the FCC bases its spacing requirements on radios from the 1960s which had horrible adj channel rejection...in Austin, 93.3 was a Class C move-in that is only 400khz away from other Class Cs...the 93.3 signal is less than 35 miles from the other Cs where normally it should be 65+ miles...it moved in before the current rules were adopted and granted a waiver under grandfathering.. there is NO interference whatsoever
And much of the world allows second adjacents in the same market. It is not a problem, and never has been even going back to the 60's when I built a bunch of FMs in South America.
Is anyone else just flat-out confused at this point? Although, I think Kirk's "sketch" helped me out here, and the idea does have some good concepts to borrow, I'm still not entirely sure how, in today's FM band, this wouldn't congest the band further. I'm all ears, though.
Hi-Fi and low data rate audio codec(s) = good enough for mono smartphone speakers and it minimizes cell phone network usage (Higher Fidelity stereo [or in a perfect world - discrete quadraphonic] audio codecs could be offered for a higher price for streaming users concerned about getting very high fidelity audio).
On the HD Radio digital carriers only (just the ones that would be used if there was an analog FM signal too) issue, I was thinking along the lines of a type is signal that wouldn't be FM and would (probably) be ignored by the vast population of FM radios yet use existing tech.
If all HD Radios could tune in the even FM frequencies, then the low power HD Radio carriers placed around even frequencies should be far enough away from other FM signals (local and nearby markets) to not interfere.
Kirk Bayne
On the HD Radio digital carriers only (just the ones that would be used if there was an analog FM signal too) issue, I was thinking along the lines of a type is signal that wouldn't be FM and would (probably) be ignored by the vast population of FM radios yet use existing tech.
If all HD Radios could tune in the even FM frequencies, then the low power HD Radio carriers placed around even frequencies should be far enough away from other FM signals (local and nearby markets) to not interfere.
Kirk Bayne
Sone of what you're describing sounds like the "FMeXtra" standard in the early 2000's, which was built to run inside the FM carrier the same way RDS does. I wish that FMX had a better run, honestly.
Also, several of my home radios have 100 khz spacing on FM!
Something to consider; is currently estimated penetration of HD radio receivers, primarily factory installed in vehicles, is around 21%.
The risk of pushing 80% of listening away from radio to streaming or something else by forcing analog out becomes very likely.
To me, that wouldn't be any benefit to radio's existence. More than likely, could hasten the end.
The risk of pushing 80% of listening away from radio to streaming or something else by forcing analog out becomes very likely.
To me, that wouldn't be any benefit to radio's existence. More than likely, could hasten the end.
The problem with Kirk's sketch is that it assumes the HD carriers occupy less bandwidth than they actually do. I can't find a real link on the NRSC website, but if you do a search for "nrsc 1026sf" you'll get a link to the pdf. Page 8 of that PDF details what an all-digital FM spectrum would look like. As you can see, despite the fact that HD radio is touted as "in band, on channel" it is actually "in band, adjacent channel". In Kirk's proposal, the HD carrier of the 94.7 signal would drown out KCMO and the HD carrier of the 94.3 signal would drown out KFKF.
Ironically, probably the best way to increase the station count on FM would be to eliminate HD radio and transition to a different allocation process that allows for 2nd adjacent channel spacing in metro areas (as discussed previously) and more relaxed 1st adjacent channel allocations. Most radios built since the 1980's have much tighter filters than the FCC allocation rules allow for. If the 94.5 frequency in Kirk's sketch were allocated a new station and the 94.3 and 94.7 frequencies were allocated to new stations in an adjacent market that would likely serve the public better than adding new HD signals.
Dave B.
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