Are such radios sold in the USA via the internet? Is the station really "fixed"? Someone gave my uncle a radio which is said to have a special "chip" that receives a Greek radio station. He mentioned to me that years ago he had another one that suddenly switched to a Philipine station and he gave it to a Filipino colleague. Amazon and Alibaba have such Metrosonix radios but not station specific, but also do not seem to allow being sold in the USA. THe search terms I used were .
Yes, but not quite in the way you describe: In the USA, additional SCA carriers used to be quite common on most FM stations. They were used to subscription handle background music (MUZAK), commercial free radio, and all kinds of data broadcasting (stocks, paging, sports scores, traffic reports, etc).
Most of that died starting in about 2002 with the introduction of digital FM radio. The IBOC signals occupy the spectrum just outside of the normal FM stereo signals formerly occupied by SCA sub-carriers. SCA and IBOC cannot coexist on the same frequency.
In the USA, FM broadcast channel spacing is 200KHz. Stations licenses in a given geographic area are assigned on alternate 200KHz slots giving broadcasters a 200KHz guard band to allow for junk receivers with rather wide IF bandwidth. SCA sub-carriers never went above about 80Khz, so there was no increase in occupied bandwidth. IBOC changed all that by grabbing all the spectrum between +/-100kHz and
+/-200KHz: Such an IBOC transmitter is now transmitting on top of the adjacent channels frequency. If the adjacent channel is not occupied, no problem. If there's a station there, big problem.
In some parts of Europe, FM stations are assigned on 100KHz channel spacing, making both SCA and IBOC an impossibility. I don't know which countries are like that.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Tradionally SCA was used for "elevator music", it was a subcarrier on an FM broadcast station, a way for the elevator music company to distribute its product. You could build your own SCA adapters, once ICs came along they were really common in the hobby magazines, but it was one of those things that you couldn't share the results with someone else. It was for private listening only.
But yes, then at some point it was a way for "ethnic" broadcasters to beon the air without the expense of a full FM transmitter, or getting a license. We had some of that here. I think the stations were hoping to be the source of the radios with the adapters, an income stream ofsome sort.
But I haven't heard of such things locally. One thing that happened in at least one case was they were able to leap to their own transmitter (though if I'm remembering right in that case, the station is now up for sale, it not being profitable for that market). So maybe it was an intermediate step, get the listeners, then jump to a full transmitter when you had the listeners.
I'd be kind of suprised if any of those stations were still active.
Here in Chicago, it was probably the early 90's that was the height of popularity, I think there were 2 greek stations, one polish and 3 or 4 others that were probably used for pocket pagers (normally silent except for bursts of tones or a data carrier).
The basic idea was the "broadcaster" would get the station from overseas (probably via a C-Band dish/receiver) and rebroadcast it on someones sca channel (an ordinary FM station set up for it). They would then rent the modified radio for like $5 a month or sell you it with a "lifetime" subscription for $100 or around there.
Usually the radios, which were cheap garbage imports, were fixed to the primary channel by crazy glueing the tuning shaft or otherwise disabling the tuner. The boards were just simple 4 wire things, power, ground, detector in and audio out. Since they were meant as a dedicated service, there wasn't any reason to make the radio work both ways, normal and special. These were all handmade and varied quite a bit, depending on what make/models the local wholesale importers had.
The adapters were numerous, the most basic/simple one used a PLL chip (either NE565 or NE566, maybe) and off the shelf resistors and capacitors. They usually worked well enough but had problems with leakage from the main carrier. There was another design, I want to say MC1340 as the centerpeice which had the best performance (dead quiet) but required custom rf coils and oddball capacitors, still simple to build but upped the cost quite a bit.
In any case the boards were probably not even 2"x2" and were easily tucked in somewhere, usually the battery holder (4xC or D cells).
As far as legality of them, although I don't think anyone considered them a crime to own, you couldn't open up a cottage industry by building them and selling them. There was no reason to stop anyone from making one, but they fell into that gray area where selling one was in some violation of FCC rules and regs for 3rd party interception of a private (or intended private) broadcast.
The thing is, once the internet and access to it became the norm (early
2000's), I really don't think those rebroadcasters could survive. On nearly any platform or device there is usually one or two applications available for listening to radio stations from aroound the world, if not dozens of websites that retransmit them.
I'd guess there are plenty of 80+ year old grandmothers from the old country who can work turning on and off a radio rather than firing up a laptop but I doubt there is enough to make any money off them.
What little I've done with broadcast FM was at various radio stations and designing some low end receivers. That was also long ago, so I'm fairly well behind on the technology. However, if "high end" means "high price", I've fixed a few of these systems:
If you've ever swept a decent analog FM receiver, you may have noticed that the IF bandwidth is much wider than the occupied bandwidth (200KHz) of the signal. In order to keep the group delay fairly constant within the IF bandwidth, this was necessary. That meant that while the audio was very good quality, the receiver would pickup junk from adjacent channels. Sensitivity is limited by the receiver front end and is unaffected by the wider bandwidth.
Roll forward a few decades and we are now blessed with all digital receivers. The best example is the Sony XDR-F1HD tuner: These typically sell on eBay for $150 to $250 or $500 with some necessary modifications. Seems to be a demand: The difference is that this receiver has a "brick wall" digital IF filter that doesn't need to be excessively wide in order to get low group delay and low distortion. The narrower bandwidth is also good for reducing much of the alternate channel noise produced by IBOC (HD Radio) signals.
Meanwhile, the lower end FM receivers are also deriving benefits from digital IF and demodulators. The Sony tuner uses an NXP/Philips SAF7730 chip while most of the low end stuff uses various Silicon Labs AM/FM chips: Basically, it's almost an SDR (software defined radio) with most everything in a single chip. Tecsun uses these chips in their various radios. Plugged into a proper audio amp and speakers, they sound very good, with little IBOC junk from the adjacent channels. (Note: Not all Tecsun radios use digital receiver chips).
No, it's not, at least in the USA. The FCC, in its infinite wisdom, has endorse exactly one proprietary and expensive standard (IBOC) totally owned and licensed by iBiquity. As usual, half measures don't work. In this case, the broadcast industry wasn't quite sure if they were going to commit to doing IBOC, so instead of 100% digital FM, iBiquity was forced to provide the half ass analog/digital compatible system that we're cursed with today. Incidentally, the failed AM stereo system following a similar life cycle demonstrating that the FCC and the industry doesn't learn from their expensive mistakes.
In 2012, a made a graph of the number of HD Radio stations in the SF Bay area and in the USA. There's actually been a decrease in stations, that have unplugged their HD Radio equipment since 2012 but I don't have numbers handy.
I know little (or nothing) of what's going on with DAB (digital audio broadcasting) as it's not used in the USA:
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
The digital noise is commonly a problem as the result of the way stereo demultiplexing works. The higher-frequency components of the FM detector's output are mixed against the 38 kHz local oscillator, thus doing an AM demodulation of the L-R subcarrier band which lies on either side of 38 kHz.
Many MPX decoders use a simple switching-mixer architecture, and these will end up detecting both the signal around 38 kHz, but also whatever is present in the neighborhood of the third and fifth harmonic of 38 kHz. Since that's where the digital subcarriers often line, the digital signal ends up as sideband noise in the L-R difference signal, and (unless you switch the tuner to "mono") ends up in the left and right channel audio.
There are a number of ways to fix this. One is to filter the FM detector output signal before it goes to the MPX chip... either a low-pass filter (knee somewhere about 60 kHz), or notch filters centered on the odd harmonics of 38 kHz, or both.
Another approach is to demodulate the MPX signal using a design which is inherently not sensitive to the 38 kHz harmonic regions... e.g. a true multiplying mixer using a 38 kHz sinewave local oscillator (rather than a square wave or switching design), or a Walsh-function decoder using a stepped wave which has no 3rd or 5th harmonic content (some Sansui tuners do this).
Modern DSP-based MPX decoders could do any of these.
That article is on HD Radio (IBOC, iBiquity, dismal radio, etc) and not about conventional FM stereo. While the mechanism for generating the noise that you don't want to hear is similar, the technology, solutions, and sources of noise are quite different. For example, there's no mixing required for the excessive occupied bandwidth of IBOC to ruin your day.
Incidentally, Brian Beezley has written several other articles on HD Radio and tuners: See "HD Radio" section at lower right and various equipment reviews at the upper right.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
SCA usage predates FM stereo. Originally there were two subcarrier frequencies: 43 kHz and 76 kHz. As stereo broadcasting became popular, the 43 kHz channel was abandoned due to interference. While some broadcasters may have synchronized the 76 kHz frequency with the 19 kHz stereo pilot, this was not required. Plus, since the SCA signal itself is frequency modulated, locking it to the pilot would not accomplish much in any case.
Next we need a thread on what all they crammed into the NTSC TV signal. Like PRO audio which was another SAP essentially, the VITS or VIR, closed captioning, ghost cancelling reference and who knows what else.
Man's innate lust to cram as much as possible into any given bandwidth.
With TV, they wasted it. They went digital because NTSC takes too much bandwidth and has limited resolution. The problem is they cannot come up with any decent programming anymore.
In other words, the resolution doesn't matter if there's nothing to watch. I don't need 2,000 line resolution to watch Gunsmoke. Just like I don't need 24 bit/96 KHz sampling to listen to music from the 1960s.
No. They had a system first in use in the late 1930s, and times changed. but they didn't want to start again, so they added that stuff, don't forget color came in the fifties, tacked onto the existing B&W standard, but it never improved the picture quality (though no more fussing with the vertical or horizontal hold controls, actually the tv set I got in 1982 didn't even have them (or at least not on the outside).
I actually got my first tv set since 1982 because of the changeover. I thought about just getting a converter, but decided spending a bit more meant I got closed captioning, stereo sound, much better image quality, and of course I got rid of the CRT and went to LCD.
I notice a difference. After 70 or so years, it made sense to actually scrap the old and move into the future. One might hope that this "standard" can be extended if needed, so there won't be a need to start from scratch again in the future.
Digital would take more bandwidth, except they use compression to reduce the amount of data sent. In the 1950s, there was not enough computing power in the whole world to do the compression and decoding in real time.
Actually, NTSC color makes pretty good use of bandwidth when you're constrained to all-analog, vacuum-tube technology. When it was introduced, compatible color was right at the cutting edge of (or maybe a bit beyond) technical feasibility for commercial (not to say consumer) electronics.
Actually, NTSC color makes pretty good use of bandwidth when you're constrained to all-analog, vacuum-tube technology. When it was introduced, compatible color was right at the cutting edge of (or maybe a bit beyond) technical feasibility for commercial (not to say consumer) electronics.
Isaac "
And ATSC 1.0 color gamut is actually a hair smaller than that of the NTSC it replaced.
You lost me there, what do you mean by that ? The different broadcasting fo rmat should have nothing to do with the colors that can be displayed, that is a function of the panel, or CRT. (actually a plasma panel is like a CRT in a way but it just has multiple rays)
Now LCD panels might be limited by the backlight. They cannot display any c olor that is not in the spectrum of the backlight. Actually they could not handle the colorimetry required for LED backlighting until recently when th e new generation of LEDs cam out that actually have a phosphor.
Older LEDs had very spikey outputs. If a color isn't there you must display two colors opposite the wavelength you want in the right proportion so the eye mixes it. It was just too much to deal with so they went with the CCFL s.
jurb...gmail.com wrote: "You lost me there, what do you mean by that ? The different broadcasting format should have nothing to do with the colors that can be displayed,"
To the contrary. A display may be capable of limitless color and dynamic range, but it can reproduce only what it is sent.
ATSC has no standard color gamut. Even with caps-lock, there is no STANDARD color gamut in ATSC. Rec. 709 is common for HD programming, and Rec. 601 is common with SD. But ATSC doesn't care; the primaries and the white point are specified in the stream. Maybe someday Rec,
2020 will be standard in a future version of ATSC, but for now, there is no such thing as an ATSC standard color gamut.
.... wrote: "STANDARD color gamut in ATSC. Rec. 709 is common for HD programming, and Rec. 601 is common with SD. But ATSC doesn't care; the primaries and the white point are specified in the stream. Maybe someday Rec,
2020 will be standard in a future version of ATSC, but for now, there is no such thing as an ATSC standard color gamut.
- show quoted text -"
Butt the f out!
Find someone worthwhile to stalk. Like someone you actually know.
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