I am curious to where radio is going can FM and AM be used other than listening to sound?

You can but why would you want to?

The cost is high for the equipment and monthly transmission charges and the geographic coverage area is small.

One of my first jobs in the real world, was as an engineer for a company called Seiscor, they made oil field monitoring and control equipment, and it transmitted digital data over FM radios.

Had a baud rate of 33. Thats 33 characters per second.

But it worked.

They also had a "tower light "monitor for radio/tv stations, that sent a signal, if the red light at the top of the tower went out.

How about an "open" FM band (liberty). Any kind of signal (AM, FM, TV, INTERNET BROADCASTS, taxi cab radios, etc), as much power as you can afford. No regulation.

33 baud is more like 3 or 4 characters a second using the accepted definition of baud. That's fast enough for a lot of remote monitoring equipment that don't have much to tell anyone.

The FM band is currently being used to send data, as in IBOC and RBDS.

Of course you specified two way which is not currently being done, but it could be. you would have to have much more power in the consumer end transmitter to be two way and hit a 100kw FM signal form anywhere within its footprint. the obvious answer to that is as someone mentioned on another post multiple transmit locations all over a city of interest.

More importantly...

Can the FM band be used for sending interesting, compelling, entertaining, interactive, local focused programming?

How about sending music videos on FM? Is there enough bandwidth for that?

Yes, 3 plain old NTSC TV channels will fit!
88.0 - 94.0
94.0 - 100.0
100.0 - 106.0

Microsoft has watch that uses FM Broadcast subcarriers.
http://news.com.com/2100-1041_3-6083432.html

Old idea... in 1990 (or so) I bought a pager watch made by Seiko/Receptor. It functioned as a normal pager as well as providing weather reports, stock market updates, game scores, and other information.
Data was transmitted to the watches on broadcast fm subcarriers, rather than the "normal" 450 mhz pager frequencies.
The Receptor company (AT&E) was local (Tigard) at the start, so the first service was the Portland area.

kgw--In Japan, the first three VHF channels reside in what we consider the FM Broadcast band. Channel 1 is 90-96 MHz, channel 2 is 96-102 MHz, and channel 3 is 102-108 MHz. Their FM band is 76-90 MHz.

The question as originally posed in this thread is very broad. Could signals other audio be transmitted in the AM or FM broadcast bands? Of course they could be. Can data transmissions be done in these bands? Yes.

There is a semantic problem occurring in this thread, with regards to the terms AM and FM. AM and FM are analog methods of transmitting signals by radio, but the layman is thinking of the respective broadcast bands when he sees those terms. The proper engineering question here is whether the parts of the spectrum where "AM" and "FM" broadcasting take place today (520-1710 kHz and 88-108 MHz, respectively) be used for other purposes someday.

If the current 88-108 MHz band were one day used for on-demand data streams, then the infrastructure would have to change from what we have today (a high powered transmitter at some central location) to a cellular type of system. This is because it would not make a lot of sense to broadcast a data stream for a single user to all of Portland. This idea is not mine but was discussed in another thread on this board.

Years ago, I read of a small AM station which leased a subaudible signal to the county for synchronizing traffic lights. I cannot remember the call letters or city, but that contract apparently covered the bills to keep an otherwise unviable small-market AM station on the air.

In the '60s, I remember reading (in Popular Electronics magazine?) about U.S. elevator music-playing FM stations that transmitted some sort of audio marker that was used by specialized receivers to mute the audio during voice tracks, IDs and commercials. The receivers were sold to retailers and offices as part of a Background Music Service in competition with Muzak.

The article explained how to build your own modifications to a radio that would allow you to do the same thing without paying the station a fee.

SCA was used,and may still be in use? for muzak and elevator music.There were receivers for it,some "standard" receivers had a switch to select it,or you could build a kit and add it on to your existing tuner.

It might have been abandoned for RDS though,I'm not sure.

I believe SCA is still in use because every time a new technology comes along, someone always wants to protect it. My only experience with an SCA receiver wielded poor fidelity with a great deal of noise and the main channel trying to override it.

KJIB used to run something called Physcians' Radio Netowrk (PRN) on a subcarrier. It was, of course, radio for doctors and was mostly spoken word...news for docs. It had lots of ads for various prescription drugs and other things of interest to the medical community.

It required a special receiver and, as I recall, the signal wasn't the greatest. Sometimes it had a phased, swooshy kind of sound to it.

Muzak still uses SCA in a few markets including Portland. In Portland the SCA is UHF instead of FM at 67 and 92 which are the standard frequencies.
The fidelity is subpar as compared to our digital satellite signal so we only use it where the satellite dish is objectionable.
At some point we will no longer have enough subscribers to justify the monthly fees and will have to convert the remaining systems to another delivery system.

Indeed it is possible for FM Stereo, SCA, RDS and IBOC digital to exist together on one broadcast FM channel... In the Portland area, KBOO (90.7) is one example of this.

"In Portland the SCA is UHF instead of FM at 67 and 92 which are the standard frequencies. "

You are mixing apples and trucks. UHF is a band of frequencies. FM is a modulation method.

Within the 200 kHz bandwidth of an FM station, there are different sources of "stuff". The first 15kHz is the standard L+R mono signal of the station's signal. Additionally, you have a 19kHz pilot carrier and the 38kHz DSSC L-R component of the stereo signal....which goes from 23-53 kHz. Above that, you have a variety of things available out to the 200 kHz bandwidth. Two of those are the SCA standard frequencies of 67 and 92 kHz. Those can have different things. Muzak uses those frequencies to attach their signal to the FM signal. Normally, those are limited to 5-7.5kHz, hence the lower fidelity.

Does UHF in this context mean something different than Ultra High Frequency? For some time, I had been wondering whether anyone puts digital subcarriers instead of the traditional narrow band FM subcarriers at 67/92 kHz.

Years ago, I experimented with building SCA decoders, with not-so-great results. In my experimentation, I noticed that the SCA subcarrier suffered from a lot of intermodulation with the main channel contents. Some people with experience in SCA technology told me that there are two things that professional SCA systems do to get around this:
1) The main FM detector in the receiver is a dual-tuned quadrature detector instead of the single-tuned circuit that is commonly found in low cost FM Stereo radios. This helps to reduce distortion.

2) An outdoor yagi antenna is used, and if the station transmitting the SCA subcarrier is using circular polarization, the receiving yagi might be oriented at 45 degrees with respect to the horizon. The 45 degree tilt is supposed to help cut down multipath.

I think that UHF in this case does mean ultra high frequency. In the past, I have logged what I called "background music" on 956.410 and 956.436 Mhz (in narrow FM mode). I just now checked these frequencies and don't hear anything... perhaps wet trees, soaked antenna have killed reception today, or they may be no longer using these frequencies?

Didnt MUZAK belong to KPNW at one time ?

Seiko had an entire division dedicated to this. Remember the Message Watch from the early 90's? It was a pager/watch that also received sports scores, lotto numbers, dow jones, etc... It sent its signal via the FM-band.

See 11/03/06 7:48 pm post above, and welcome, Dude!

"Man that rug really tied the room together"

This topic is confused. It depends if the basis for the question was "under present FCC rules" or not.

Do the rules allow something other than analog audio (voice/music) on the main carrier?

Do the rules allow something other than analog audio (voice/music) on the main carrier?

Yes. The rules have been relaxed a bit on the area above ~60kHz.

Isn't 956 mhz nearly SHF or super high frequency?

Guys, I believe the subcarriers used for SCA, like the stereo subcarriers at 19 and 38 kHz, are amplitude modulated. The subcarriers themselves are like an ultrasonic "tone", part of the frequency modluation of the main carrier along with baseband audio, but those subcarriers are then modulated by amplitude.

AM for the subcarriers, along with suppression of one sideband, is why they can all fit on the main signal. It's also why the signal-to-noise ratio of the stereo subcarrier degrades in fringe areas before the main, FM carrier.

Interesting that 7.5 kHz was once considered a severe compromise in quality. Now, it's hi-fi compared to what some AM stations are doing at night.

Semoochie asked:

"Isn't 956 mhz nearly SHF or super high frequency?"

I thought the band edge *might* be 1000 mhz, but the definition of UHF is 300 to 3000 mhz. This chart shows the band structure with links to services in each band (some don't work). The "classic" definition, which makes the break between bands on the "3" is bent a bit, perhaps to avoid splitting services into two bands... for example a service from 2900 to 3100 mhz is listed as SHF.

http://www.jneuhaus.com/fccindex/spectrum.html

Some time ago, I read that broadcasters are free to use any modulation technique on their SCA subcarriers, as long as the level of these subcarriers is kept below some limit defined by FCC regulations (see FCC link below).

The SCA subcarriers that I have run across were indeed low-deviation FM. When experimenting with SCA, I looked at the subcarriers (after filtering) on an oscilloscope. There were slight amplitude variations that coincided with the main program audio, but these were obviously not intentional.

I tried two ways of decoding SCA: using a 565 PLL chip (Radio Shack used to carry this part, and their databook used to have a schematic for an SCA detecoder) and using a narrowband FM receiver chip out of an old cordless phone. Neither decoder sounded very good. The PLL chip decoder had some subtle heterodyne squeals accompanying the sound in addition to "splatter" from the main channel. The narrowband FM receiver chip didn't have squeals, but there was still splatter. I learned two lessons out of this:
1) When you do low-deviation FM, you save bandwidth, but you pay in noise. The SCA subcarrier only deviates by about +/-5kHz, so the quality won't be much better than if AM or SSB were used.
2) Regular FM Stereo tuners usually don't pass the SCA subcarriers faithfully enough for good reception. Low distortion detectors and possibly wider IFs are needed for good SCA reception.

Wikipedia page on SCA (with examples of uses for subcarriers):
http://en.wikipedia.org/wiki/Subsidiary_Communications_Authority

FCC page on SCA:
http://www.fcc.gov/mb/audio/subcarriers/

I remember the break on the 3s now that you mention it but hadn't thought of it for over 30 years(hey, another 3)!

None of the sidebands of the Stereo L-R signal
is NOT removed, rather, the subcarrier is suppressed.

Double Sideband Suppressed Carrier

The L-R is amplitude modulated onto a 38 kHz suppressed carrier to produce a double-sideband suppressed carrier (DSBSC) signal in the range 23 to 53 kHz.
A 19 kHz pilot tone, at exactly half the 38 kHz subcarrier frequency and with a precisely defined phase relationship to it, is also generated. This is transmitted at 8-10% of overall modulation level and used by the receiver to regenerate the 38 kHz subcarrier with the correct phase.
The final multiplex signal from the stereo generator is the sum of the baseband audio (L+R), the pilot tone, and the DSBSC subcarrier (L-R). This multiplex, along with any other subcarriers, modulates the FM transmitter.

By removing the subcarrier, the amount of power in the sideband is greatly reduced. Otherwise there would be a much
higher power requirement to transmit both the baseband and sideband signals the same distance. Other considerations require the use of pre emphasis of higher frequencies at the transmitting end to overcome the noisy nature and easily damaged nature of the sideband because it is propagating at the outside regions of the waveform and tends to get bruised when it bumps into stuff.

http://mediaeng.com/baseband.html

http://en.wikipedia.org/wiki/FM_radio

SCA adapter kits and modified portables: http://members.aol.com/fmatlas/home.html

Also, the only source I know of for TV-SAP radios (for those having friends who want a more convenient way to hear Golden Hours.)

Golden Hours will soon be on HD3.

While SAP is a stronger, clearer signal than SCA, its accessibility to the blind plummeted when program-selection switches on TVs gave way to remote-controlled on-screen displays (and then DVI cut ito GHR's hours). I would imagine an HD subchannel will be no easier to select.

GHR is promoting "web appliance" stream receivers which are easier to operate than a contemporary TV or computer, though I don't know if they're available yet, they require a subscription to use, and will tie up a landline if DSL or cable are not undertaken at additional expense (though metropolitan wi-fi, when it gets here, may offer an alternate, albeit geographically limited, delivery method).

This is essentially a step back toward the original leased-line distribution.

Putting RRS's on cable as a TV audio and/or FM channel (offered at ultra-basic service level as community access) would probably make a better solution, though analog cable channels are now all booked up, and I know few folks who bothered or even knew how to connect an FM receiver to cable.

(Some here may remember pre-MTS when HBO's stereo audio was carried on FM cable.)

HD subchannels are *easy* to select (on the limited number of HD sets that I have used). There is no complicated menu, like the TV sets have. If you are on the main channel (and it is in HD) just punch the "up" button or click the tuning knob up one notch to get to HD-2. I assume one more punch or knob click will jump to HD-3 (can't test yet in Portland). HD subchannels can also be stored as presets, for easy selection.

Yep... pre-MTS TV stereo on FM on cable... MTV was on in stereo in my area using this system.

Well, that's good news. I haven't examined an HD TV. (Will have to go back on basic cable when analog to air ends.)

Oh! I was talking about IBOC FM HD... Golden hours will soon be on be on HD-3, I assume Semoochie was talking about FM here ?

The HD-TV tuners work much the same way... easy to navigate through all HD channels and subchannels with up/down punches of the remote.

Yes, I was talking about FM HD. From what I understand, AM HD doesn't have the ability to transmit multiple signals.

Last night, perhaps storm related, KOPB-FM (91.5) was off the air for a while, but their HD-FM transmitter continued to operate.

KOPB became one of those "hidden channels" that the HD advertisers tout... "normal" KOPB programming was only on HD-1, rock music on HD-2... no sign of HD-3, Golden Hours yet.

OPB must be shuffling equipment around; while 10 blinked when the lights dimmed last night, there have been other glitches for over a week.

Sorry, let me just sway this topic back to the SCA point for a second:

88.3 has what appears to be Russian programming on its 67. KBOO has Korean on 67 and Vietnamese on 92.

KMHD used to have some kind of Teletype on its 92 but it shut down July of 2005.

This was observed at my home in "The Coove", about 2 miles away from the 1550 towers (near Evergreen High school, basically) on a modified Sony ICF-36. (Thanks again Dr. Elving, if you are reading this!)

Love the Radio Entertainment Network during the weekends on Golden Hours (Ch. 10 SAP-78.62kHz), by the way.

Now, swaying back to the main topic..........

Um, yeah, it can. Whaddya want?

Another use for the FM sub-carriers was for paging.

Back in the late 1980's and early 1990's there was a company that was using the sub-carriers for numeric and alphanumeric paging. They were trying to build a nationwide network using FM stations. I don't remember their name.

The pager scanned all the FM frequencies looking for an idle tone to lock on to. There was usually only one station, but sometimes two, in any given market that the paging company would contract with to carry their data.

I also don't remember how the data was delivered to the radio station whether it was via satellite or telco...It was too long ago!

They had building penetration issues with their signal as the receiving antenna was inside the pager and therefore only some very small fraction of a wavelength.

The company pretty much went away after SkyTel built their 931 MHz. nationwide paging system and other paging carriers built their networks.

When I was in the AF, working on F4 Radars, and missile guidance systems, I learned, part of the AIM 7 air to air missiles guidance system is an FM signal that carries info to the missile, and it also uses an AM signal for other info.

And it isnt music for the target aircrafts enjoyment.

Decades ago, WLW-AM in Cincinnati used frequency-shift keying on its carrier, a form of FM, to send slow speed morse code messages to US operatives in Cuba and elsewhere. It was undetectable to ordinary listeners.

I have read about SCA's being used for paging.

I think some areas might still have SCA's in use like that...but I know Portland doesn't, at least none that I have heard...........

Why would WLW want to spy on anyone in Cuba?

WOR was another station that experimented with using FSK for low speed data transmissions for the government. I wasn't aware that any of this had gone beyond the experimental stage.

This is actually a brilliant idea because WLW and other 50kw clear channel stations would get a pretty stable signal into that area nightly, and the Cuban authorities wouldn't expect that the U.S. government would "hide" messages to its operatives in the signal of a commercial broadcast station. To think of all the time that Castro's people probably spent looking for these types of transmissions on the shortwave bands--heh, heh, heh!!

FSK has a weakness, and it is it's inability to penetrate high multipath environments. In fact, on the comm. FM band, any subcarrier at subcarrier frequencies above the main, pilot and diff signals are at the outside of the envelope and suffer from a host of transmission/reception anomalies. Think 3D ... the L+R is at the core, the pilot a thin sphere around it, covered by a thicker sphere which is the L-R. SCA Subcarriers and their modulation are even further out there, like outermost electron shells orbiting the nucleus. They are the part that gets bumped into the most by conditions non conducive to propagation.

How about using ASK on a FM station?
ASK = Amplitude shift keying.
To send secret messages of course.

I don't know, you'd have to ASK an expert.

A narrow-shift FSK teletype network using the carriers of AM BCB stations was proposed in the sixties, and probably built, though whether it was ever actually implemented remains unknown. http://www.rl.af.mil/History/Communications/MFSurvivable.GIF is a map showing its arrangement in the Northeast.

It (or something else but similar) was apparently also known as "BROFICON" (Broadcast Fighter Control). Available details are murky; a lot of weird defense ideas were proposed, tried or only briefly used during that era. Most proved unfeasible, uneconomical, or were quickly obsoleted by the shift from bombers to ICBMs.

Two decades ago a KFI engineer found panels at the transmitter labeled for (previously removed) switches for FSK RTTY operation, plus an old teletype test tape. Whether this was defense related or (my guess was) part of an early earthquake-resistant police/fire emergency network hasn't been determined. (It had a home-brewed look with label-gun markings, which doesn't sound military to me.)

While WLW got into Europe very well on its wartime experimental power of 500KW, its penetration into Cuba is not as good as some other U.S. clears. While many remember WLW being used for the "special broadcasts" to Cuba in 1962 (when it was reportedly still capable of making 500KW), other old engineers have contended a couple different stations were used then instead.

One well-known use of BCB carrier FSK was WIOD's longtime relaying of the Navy Fox broadcast (presumably to Gitmo), using a +-10hz shift; see item 23 in Barry Mishkind's FAQs: http://www.oldradio.com/current/bc_am.htm Also interesting is the BBC's use of FSK for power grid load shifting control during the sixties. In the thirties some experiments in broadcast fax were made by newspaper-owned stations.

Well, this is ancient history now and probably off-topic, interesting only to geezer geeks like myself. But those over 50 here may remember hearing the pilot tone broadcast all night by KNBR until about 1963 as part of CONELRAD. http://users.adams.net/~jfs/belmont.htm

Outsider, WLW was just a distribution point for the State and Defense Departments.

If I recall correctly, there were three AM clear channel signals which were given experimental "super status" by the government in the 1940s. They were upgraded to a half-million watts, but the government had more direct access.

In the days before the Emergency Broadcast System, the idea was that these three stations could cover the entire country if all other communications had to be shut down.

Andy, if I recall, the FSK on WLW was at some very low data rate, to avoid propagation issues, and to prevent CW keying transients from being audible using ordinary AM radios without BFO.

I had an older friend years ago who consulted on the design and construction of that big transmitter at WLW. He said the modulation transformer had its own building, and was cooled with water circulated through an outdoor pond.

He also said there was a constant PR battle regarding the intensity of the RF field. Any loose or rusted metal in the area would receive the station, some people had lights that stayed lit when they turned off switches, making it hard to sleep at night. At one point some guy set up a hot dog stand a few blocks from the transmitter, with the franks connected directly to a dipole for cooking.

I remember , i think it was the 80's with experiments in sending an emergency signal over normal radio broadcasts, that would turn on your radio if it was off, so you could hear tornado warnings, etc.

First proposed in the early seventies as a civil defense system, but being late in the Nixon administration, people found the idea of the government turning on their TVs and radios to make announcements too scary. The proposal was to make the capability mandatory for all AM/FM/TV receivers, and for a capable receiver to be mandatory in all vehicles.

Instead, NWS incorporated auto-alerts (tone selcall) into their new VHF system around 1976, but coverage was spotty (and remains incomplete). I remember having to log its screeching tests when on Coast Guard radio watch from a plain Motorola receiver we had to put across the shack in the window to get enough signal.

There was also WGU-20 on longwave, now gone. http://en.wikipedia.org/wiki/Wgu-20 and http://www.geocities.com/radiojunkie3/WGU20.html

The idea of auto-activating broadcast receivers is being floated again in the Homeland Paranoia era.

However, while running errands the other day and seriously wondering whether the wet pavement was going to freeze in the evening, it occurred to me I could just take my Sony Walkman (with WB) along and plug it into my cassette adapter for mobile use. I'm not sure I could find up to moment wx info quickly on regular local broadcast these days.

China recently looked at various means of distributing alerts and found one based on their cellular phone system would be most effective and cost efficient, as cell phones have become the primary means of communications in many areas of the huge country. Some tests have been made on something similar here.

(Well, while we've wandered off-topic into weather alerts, I might as well mention Roseburg's "Mount Nebo Goat Reports" of the early 70s on KRSB, when it was discovered the distribution of the goats on the mountain were a more accurate forecast than what they were getting from NWS PDX in those days... After it was written up in Reader's Digest, they became the "World Famous Mount Nebo Goats.")

The weather station's announcer sounds a bit robotic. Anyone know his name?

Otto.

Ha. The first synthesized voice, "Perfect Paul," earned the nick of "Sven" because of his pronunciation. He was replaced by "Craig" and "Donna" in 2002. http://www.nws.noaa.gov/nwr/newvoice.htm

In 2003, "Tom" was added, who can emphasize when needed. http://en.wikipedia.org/wiki/Weatheradio

Sidebar: If memory serves correct, Perfect Paul was a Kurzweil invention (I even remember seeing/hearing a Kurzweil "Reading Edge" reading machine which used Perfect Paul as its default voice.)

I think Craig and Donna might be Lernout & Hauspie "people" like Microsoft Sam is.............

Whoops sorry--they are Speechify voices, using actual recorded samples of human speech which are then strung together by the computer to produce the spoken output.

Kinda' like how a Wavetable systhesiser--your computer most likely has one in its sound card--produces very realistic sounding music when compared to the old-skool FM synthesis method like the old Ad-Lib and a bevy of others employed.

(I remember reading this on some page about synthetic speech somewhere on the Internet.....but apparently my memory isn't serving correctly................)

Yea, the one had a swedish accent. The newer voice still has trouble with saying Cascade Locks.

"Microsoft has watch that uses FM Broadcast subcarriers." A Portland group offered a watch that used the FM bands over 15 years ago!

> How about using ASK on a FM station?
> ASK = Amplitude shift keying.
> To send secret messages of course.

Intentionally superimposing AM on an FM signal has (or is currently) being done. I can think of two examples:

1) FM translators can broadcast their legal ID in Morse code. This Morse code ID can be in the form of a tone that amplitude modulates the carrier by 30% or more. Properly done, this would be inaudible on normal FM receivers.

2) The German "zweiton" stereo television system used this approach to indicate a stereo transmission. In zweiton stereo, there are two FM sound carriers. The main carrier contains the normal monaural audio. The secondary carrier is 242 kHz above the main carrier and contains either the left channel audio or a second audio program. If this secondary carrier is present, then an identification tone is amplitude modulated onto the main sound carrier.