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"HD Radio Goes the Way of the Laserdisc Player"

Tom Wells said:
I suspect it is less a problem with very narrow IF response that can be achieved in modern design.
Old radios with simple 10.7 IF transformers are probably a little too wide to keep the noise fully out,
especially when driving through multipath areas and the signal has dropouts.
Click to expand...

That's exactly the case, Tom. If you look at the "haystack" generated by FM HD, a perfect one will occupy the bandwidth up to 200 KHz above and below the assigned carrier frequency. Essentially, HD has widened the occupied bandwidth of an FM station from 200 to 400 KHz. So as you move up or down one channel with a radio having ceramic-filter selectivity ('80's vintage and newer) the receiver solidly captures the noise. A brand new radio (like the Sangeans, Tecsun's, or an HD receiver) with a digital demodulator sees 1/2 the channel full of digital carriers and the other 1/2 blank. So it can't lock on to much of anything and stays pretty quiet. Old radios with IF transformers will slope-detect the digital carriers, producing the whine that's being discussed here.

Of course, if the HD signal is gone the ceramic-filter radio and the brand new radio will be able to hear a regular analog station on that frequency.

Dave B.
 
That "whine" is not IBOC....it's the noise that Plasma TV sets, and to a slightly lesser extent, LCD TV sets and monitors make.
IBOC noise is a more muffled sound, and it only extends out a few KHz to the sides of the (limited bandwidth) audio. The "width" will seem to vary, according to how wide the receiver's bandwidth is...it will appear to be wider, by the amount of receiver bandwidth, above the actual width of the noise. (I think I verified KSL-AM's IBOC to be +/-16 KHz, by narrowing my communications receiver down to about 300 Hx BW. So, a radio with a "good" 5 KHz BW would get noise to about 21 KHz out.

Plasma and LCD hash go all over the bands, even up in to VHF. The level of noise varies a bit across the spectrum, too. Ferrites and torroids help...IF they are the right chemical "mix" for the particular frequency. The ones that come with some TVs will work from about 25 MHz to about 200 or so (assuming they are clamped on every cable coming out of the set). For AM and shortwave/HF bands, you'd need a second core, of a different type.
 
kenglish said:
That "whine" is not IBOC....it's the noise that Plasma TV sets, and to a slightly lesser extent, LCD TV sets and monitors make.
IBOC noise is a more muffled sound, and it only extends out a few KHz to the sides of the (limited bandwidth) audio.
Click to expand...

We're talking AM vs. FM here. The mp3 samples provided were from Chicago FM stations, and the noise is definitely the tell-tale whine of HD radio. In this case it's multipath causing the HD carriers to show up at a much higher level than the analog, where the analog carrier sits in a deep null while the HD carriers do not. In a couple of spots you can hear the AFC in the radio jumping frequency to follow the HD carrier instead of the FM analog carrier because it's stronger.

Interestingly enough, the HD radio pundits will say this is not significant because any radio with PLL tuning won't exhibit this phenomenon. But the number of HD radios is still smaller than the number of analog-tuned radios.

Dave B.
 
The clip with the whine was "assembled" from edits out of a longer recording and occured as I was tuning around.
I hadn't intended to stop on them, but it would be ever so easy to park on one of them and
make a good long sample. No need, it's the same sound as heard.
And the AFC was chasing between the analog and HD, but because I was tuning.
It's not causing a problem with the AFC per se, when a station is tuned in properly.
The AFC not knowing whether to follow the analog or digital sidebands does seem a new effect on out of market signals.
The Chicago dial is so full that there's not many channels that aren't occupied or iboced.
 
Bring back AM stereo. It greatly improves the product on the airwaves and doesn't interfer with other stations. Try listening to WLS or KCJJ 1630 from Iowa.
 
KyDXIn said:
Bring back AM stereo. It greatly improves the product on the airwaves and doesn't interfer with other stations. Try listening to WLS or KCJJ 1630 from Iowa.
Click to expand...

I've heard a recording of KCJJ in stereo during the great weekend "Robb Spewak Show" and it was pretty sweet sounding. Spewak has the boss jock thing down to a science!
 
If the Ibiquity system is "going the way of the Laserdisc", I'd actually consider that a good thing. That means it has a good chance of catching on. Laserdiscs are just about all I ever use. Certainly beats the lossy compressed (read: crap) output you get from DVD Video. Indeed, DVD-V historically has had a very hard time catching on here, except for the occasional "one-off" disc recorded from a DVB-S stream capture, but that's another story.

All in how you interpret it, I suppose.

[size=8pt]@Savage--
It was called "Selectavision", a brand which RCA also used for a line of VCRs. Apparently the confusion was so great within RCA that they took to generically calling it "videodisc" instead. In reality, it was a recording technique known as "capacitance electronic disc". JVC developed a similar system around that same period, but it didn't seem to get too far out of Japan.

"Spectravision" was a hotel local-area cable television system, and its eponymous company that was eventually bought out by On Command. And I believe it also went tits-up along with On-Command....
 
KyDXIn said:
Bring back AM stereo. It greatly improves the product on the airwaves and doesn't interfer with other stations. Try listening to WLS or KCJJ 1630 from Iowa.
Click to expand...


I agree with you. AM stereo sounds very good. Brightens the music and animates the programming of a well run AM.

What happened? By the time (1982) FCC allowed AM stereo and let the marketplace select the winner, three AM stereo systems hobbled out of the gate to do battle. WLS went with Harris, WJR went with C-QUAM and the majority of big guys (WABC, WNBC, WQXR, KSL, WOWO, WBZ etc) tested and started with Kahn-Hazeltine. First two were quadrature and Kahn was single (independent) sideband. Harris had a clean, linear envelope but was mono below 1Khz. MOtorola's C-QUAM had 3 things going for it; decoders ready to install - a cosine detector which measured the difference between the linear (output of the synchronous detector) and composite (output of the envelope detector) and used that signal to expand and restore the audio separation below 1Khz. The most important asset for MOtorola was their association with the autoMOtive industry. Stations bought and ran the Harris and Kahn systems. MOtorola ran its tests with Delco, then a major maker of auto radios, and had the inside track with General MOtors, MOpar and FoMOco. It cost $12,000 for an AM stereo exciter for each system. Plus you needed a mod monitor and various kinds of transmitter/antenna work to go stereo.

I know a number of auto makers began adding C-QUAM to their factory radios and installing them in new cars. I do not recall an automaker installing any other type decoder other than C-QUAM. WBZ went C-QUAM early '84. Very few radios were able to decode all systems, but Harris would decode in a C-QUAM chip after they were allowed to use MOtorola's 25Hz pilot tone. MOtorola won by default because they were the only guys to field working decoders.

1992 the FCC mandated C-QUAM as the accepted system and C-QUAM exciters have rapidly been decommissioned ever since.

Local or Class A signals sound good, unfortunately, co-channel and/or skywave interference ruins most night signals. It can be maddening to have the radio constantly switching between mono and stereo.

Although things are super in optimal conditions, C-QUAM was found to be wanting in actual MW radio operating conditions. If they'd only gone with a Harris/Kahn hybrid! Woulda, coulda, shoulda...


-
 
You are correct. Magnavox was selected first and also devised the first AM stereo decoder chip (LM 1800???). Belar deferred to MOtorola early on. Magnavox used an AM/FM scheme where the other 3 used AM/PM. It still played on the other QAM decoders also. They were basically no-shows although Belar DID side with MOtorola from the outset. Magnavox had a few stations but... Harris was banned for a time because of distortion but the FCC reinstated them. One good thing about AM stereo is the noise level only rises 3dB going mono to stereo. FM mono to stereo noise increase is 23dB for comparison.
 
KyDXIn said:
Can we do anything to get AM stations to bring back AM stereo? Seems like this would be an improvement.
Click to expand...
Sure. Give away stereo gens, mod monitors and consultants to broadband the antenna system. That should do it.
 
Get the corporate suits to stop bashing AM and realize those properties' potential to make some money. I mean, come on, already. Half the population of radio stations out there is completely underutilized and represents nothing but expense. That's bad business. SOMETHING can be done with those signals to make money.

It just takes a little time and attention, and rethinking things. To not do so is myopic and stupid.
 
Get the corporate suits to stop bashing AM and realize those properties' potential to make some money.
Click to expand...

Amen. The cluster management mentality has many groups ignoring their AM profit potential (and that applies to many of the FM's in many local clusters also).

In many situations, management meets their goal by focusing on the "cash cow" in the cluster. Other stations in the cluster are either used as flankers or ignored. Savage is right. This practice is stupid and myopic. Every station in the cluster has the potential to add something to the bottom line. To not take advantage of that potential is a poor use of the signals that the owner has paid for and poor management.

It's like having a fleet of 10 delivery trucks, but only using one or two of them even though you could run 'em all and make more money.

Since when did any signal become, "not worth the trouble?"
 
When no one under 65 was tuning in anymore?
Click to expand...

Zach, you may have meant that as a tongue in cheek comment. But if not, you missed the point. If cluster managers and their programmers were paying attention to all the stations in their cluster, there would likely be no stations drawing a predominately 65+ audience.
 
Savage said:
Get the corporate suits to stop bashing AM and realize those properties' potential to make some money. I mean, come on, already. Half the population of radio stations out there is completely underutilized and represents nothing but expense. That's bad business. SOMETHING can be done with those signals to make money.

It just takes a little time and attention, and rethinking things. To not do so is myopic and stupid.
Click to expand...

Amen, brother...but it will also need something else: The FCC will have to start enforcing Part 15 the same way they enforce local public file violations. AM won't be a viable medium if it is essentially abandoned to every noise generator in creation.
 
Zach said:
RadeoEngineer said:
Sure. Give away stereo gens, mod monitors and consultants to broadband the antenna system. That should do it.
Click to expand...

How does the cost/effort to upgrade an antenna system for C-QUAM compare to doing it for HD? Surely it has to be easier and cheaper, right?
Click to expand...

The answer is yes. For AM Stereo you need to have as good of a broadband match to the antenna as possible, but you can get away with less than perfect.
 
RadeoEngineer said:
Zach said:
RadeoEngineer said:
Sure. Give away stereo gens, mod monitors and consultants to broadband the antenna system. That should do it.
Click to expand...

How does the cost/effort to upgrade an antenna system for C-QUAM compare to doing it for HD? Surely it has to be easier and cheaper, right?
Click to expand...

The answer is yes. For AM Stereo you need to have as good of a broadband match to the antenna as possible, but you can get away with less than perfect.
Click to expand...
You'd be amazed on how much you can get with a "less-than-perfect" antenna system. AT WJIB/740 in Cambridge, MA, we were able to pass clean Stereo (C-QUAM) using our (1948 vintage) omni antenna with a Nautel transmitter at 250 watts. It covers (and still covers) the Boston area like a glove. Use some good processing (Optimod) and we did fine!
 
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