My own observations on HD Radio.

[pqgeorge]

The AM version of HD Radio seems to be very ineffective for sure. I live less than 20 miles from the WBZ tower (in Hull, MA). It is very hard to decode their HD signal, even with an outside aerial. And if it does decode, it eventually goes back to the analog signal, complete with the 8 second lagtime. The analog signal, as you would probably surmise, sounds like a 4000 to 5000 Hz phone line. To my ears at least, it's very hard to listen to WBZ due to the limited bandwidth of the signal and the constant whining/hissing in the background. And I've used various receivers both analog and digital. The real test is the Superradios II and III. I own many of these. They all sound the same. 'BZ used to have the most pristine sounding audio chain anywhere. I noticed the change in their tonal quality the moment they switched on the IBOC a few years ago. On top of it, I can no longer listen to KDKA or 1010/WINS in the car at night due to the hash from WBZ's IBOC signal. And 1010/WINS is probably one of the best all-news stations in the country. If I'm lucky, I can use my computer at home to listen to 1010/WINS. Mobile service for internet radio is still in the formative stages. I've said this many times over, trying to make AM digital with IBOC is like "making a silk purse out of a sow's ear". It doesn't work. It's noisy, interference laden and has no coverage.

FM suffers the same coverage deficit. Even at 1% injection, it causes interference to stations on adjacent channels. One station in particular has such a wide IBOC signal that stations two to three channels down are affected to where you cannot hear them from over five miles away from the IBOC transmitter. One of them is less than 30 miles away. Now imagine if the IBOC proponents got their way with 10% injection. It would be called the "AM-ization of the FM band". This would be detrimental to the stations located many channels adjacent to the IBOC station.

I was very interested in HD Radio in the beginning. I even bought a Boston Acoustics receiver over three years ago. The "OH WOW!" factor has subsided. I find nothing too compelling on HD1, 2 or 3 in the market. Anyone can grab a computer. Load up some tunes and play it in shuffle. That's generally what I've heard on HD.

Yes, the cost of HD radios have gone down. But I don't too find many people buying them. The cost of instituting HD on radio stations is exorbitant, especially if your station is a Mom and Pop, college or community station who are, more than likely, at a signal disadvantage already. Add IBOC to the mix and those smaller signals will be drowned by the more powerful IBOC station's subcarriers.

FMeXtra would be a better way to go digital on FM, by using the SCA space that all FM stations always have possessed. If you put a good FM Stereo signal on the air and people get it well (coverage), you can get a good FMeXtra signal out there as well. For the cost of the unit, about $15,000 (no license fees required, unlike HD) FM stations can enjoy full quality digital Stereo, surround-sound and multicasting with FMeXtra, just like IBOC, but without the potential for interference. The AM'ers could simulcast on one the subs of the FMeXtra station. Even the LPFM's and the grandfathered Class D's could go digital with FMeXtra.

Would I purchase another HD Radio, probably not. If FMeXtra were to grow and put to the mainstream market, I'd be the first to go and buy the radios. IMHO, FMeXtra is a better digital system than IBOC. (Soapbox mode off.)

 

[TheBigA]

For the cost of the unit, about $15,000 (no license fees required, unlike HD)

Hmmm....is that an FCC license fee you're talking about?

 

[pqgeorge]

For the cost of the unit, about $15,000 (no license fees required, unlike HD)

Hmmm....is that an FCC license fee you're talking about?

NOoooo. We're talking about Ibiquity's user license fee which requires you (the station) to pay $25,000 for the first stream, in addition to the $100,000 you pay for just the equipment itself. Furthermore, for every additional stream you activate, you pay Ibiquity $5000 for each additional stream user license fee. We're talking serious bucks here. For the conglomerates, it's just a drop in the bucket. For all the others, it's overwhelming.

FMeXtra has no license fees. You just pay for the cost of the equipment, and that is that. You own it.

 

[Play Freebird]

I agree -- iBiquity's license fee is priced unreasonably high for most smaller stations.

For roughly half that amount (including purchase of an FCC license and all necessary equipment) my business partner and I just put a 250 watt FM translator on the air to carry the programming of our AM daytimer. And it works so much better than AM IBOC!

• It allows our programming to be heard 24 hours a day
• It reaches well beyond the AM's 5 mV/m contour
• It offers true FM stereo quality
• It allows our AM audio bandwidth to remain as high as legally possible (within NRSC limits)
• It causes no interference to our AM neighbors, nor to our own AM signal
• Our listeners already own the necessary receivers and have told us that they really appreciate this new service, which will finally permit our station to carry evening high school sports and expand local news coverage

On the other hand, the AM HD alternative offers none of these advantages.

Oh, but it's "digital".

Need I say more?

 

[mgpt6]

well said Peter. I dont know why DRE has not been more agressive with FMXtra.

 

[Chuck]

well said Peter. I dont know why DRE has not been more agressive with FMXtra.

I just spent the afternoon with Lyle Henry, who is "The Radio Doctor." He is a big advocate of FMExtra. Lyle was in our area and volunteered to come out here to see how FMExtra works on a LPFM station. As far as we know, it was a first. It took us about 20 minutes to get the equipment out of his car, install it in a rack and put it on the air. It was simple.

I think that might make KZQX-LP the very first LPFM station to ever broadcast in Digital. Then again, maybe not. Does anyone know of an earlier attempt?

"So how did it work?" you ask. "Pretty well," would be my answer. We received a reliable FMExtra signal in any location that we were also able to get a decent analog signal. In locations where the analog was marginal, FMExtra would disappear. That did not surprise anyone. It did work reliably to approximately our 55 dbu contour using a simple whip antenna. Connected to a Yagi pointed at the originating station, our 74 watt LPFM was doing fine in FMExtra at roughly 14.5 miles away. I think that is very acceptable performance. It was a lot better than our analog signal does at that distance.

During the experiment, we fed the AES digital output of our Broadcast Warehouse DSP-Extra audio processor directly into the input of the FMExtra encoder. The noise floor was measured to be down over 90db. The audio quality was excellent. I couldn't find much about this to not like.

The FMExtra signal also passed through a translator. It did not seem quite as robust as the primary signal, but that may be because the translator's receiver could be rolling off higher frequencies. We are not sure, but it seems like a logical explanation. Still it was quite satisfactory.

Incidentally, we kept our RDS signal on during all this. If we had chosen to lose the RDS, we suspect that the FMExtra would be even more robust.

This "science project" has confirmed my suspicions that FMExtra is something that deserves much more consideration that it is getting. It works. It is affordable, and it doesn't create interference.

 

[mimo]

Thanks, Chuck, for that EXCELLENT real world example. This definitely lo0ks like something that should be lo0ked into further.

 

[TheBigA]

Interesting discussion about FMeXtra, but the problem remains that people need to buy new radios. They haven't been too excited about that, regardless of the product, whether it's HD, satellite, or internet. So far the only radio available for FMeXtra is made by Digital Express, and it's one of those KLH-styled table models. Not too sexy.

I think for FMeXtra to be taken seriously, they have a lot of work to do with electronics and auto manufacturers as well as retail outlets so people can buy radios.

It also doesn't help the AM situation.

 

[semoochie]

I would really like to see Ibiquity embrace FMeXtra as the first back-up so it drops in when HD drops out. The second backup should be clean mono, getting rid of multiplex once and for all.

 

[TheBigA]

I would really like to see Ibiquity embrace FMeXtra as the first back-up so it drops in when HD drops out.

They're competing companies. It's like asking Coke to embrace Pepsi or Bud to embrace Miller.

Plus you'd need to have radios that could receive both. Right now, few radios receive either.

I think what really has to happen is for FMeXtra to put together its own coalition. There are lots of stations not part of the Alliance. Go to them.

 

[Chuck]

I don't see much hope of Ibiquity and FMeXtra forming an alliance on the transmitting end, but I suspect it might be possible to have common ground on the receiving side. Since the newest generations of HD radios are really "Software Defined Radios." it doesn't take a very vivid imagination to think it might be possible to make the radio decode both formats.

Both the HD encoder and the FMeXtra encoder are simply computers with some unique input and output cards. The actual "system" is in the software. Decoding this should be fairly easily done by including appropriate software in the receiver. Since FMeXtra apparently doesn't require a royalty payment by the receiver manufacturer, it shouldn't be too big a deal to include it in future HD radios.
The precedent for such a move has already been made in the land of TV. Your new HDTV is capable of decoding several competing formats. Adding this capability did not seem to have had an adverse effect on the TV industry.

If the FCC is considering mandating the inclusion of HD on all satellite capable radios, then they ought to also mandate the inclusion of FMeXtra decoding, and probably DRM as well. There is no reason why a station couldn't use both HD and FMeXtra simultaneously, so why not make the radios capable of decoding it? While you are at it, you might as well add the capability to tune from 76 MHz to 108 MHz.
I suppose that would make way too much sense, and ruin the monopolistic aspects of any current technology.

 

[Seattleradiodude]

Speaking to one of the engineer’s at a station running 3 HD channels here in Seattle

I brought up the topic of FMeXtra. He admitted he didn’t know to much about the system
but did say that the digital SCA stream would do nothing for multipath.

Did you have any experience with this during the testing chuck? (or anyone with field experience)
Feedback would be great!

 

[radioskeptic]

Is FMeXtra more affected by multipath than In-Band, Off-Channel “HD” radio?

Yes, in theory – and frequently in practice, too, at least so far. Why? Let’s review some basics.

We all know that multipath effects can be heard in analog stereo when the mono component of the signal sounds just fine. That’s because the mono component is still wideband FM, while the difference subcarrier, being much higher in frequency, is effectively being transmitted as narrowband FM. An SCA signal, higher still in frequency, is even more affected.

True, analog SCA’s are FM, not AM (or strictly speaking, DSB/SC) like the stereo difference. But they’re narrow-band FM on narrow-band FM; they’re as dense AM signals, and just as vulnerable to multipath.

FMeXtra signals benefit a little form the all-or-nothing nature of digital decoding, but multipath can still be a problem.

But “HD” signals are very different. First, they are, by definition, not sidebands of the analog signal, because they’re not generated by modulating the amplitude, frequency or phase of the analog signal. They’re independently generated, and they have no fixed phase relationship to the analog FM signal. That explains why many older high-efficiency transmitters with Class C finals, which can’t faithfully pass even the relatively small resulting amplitude variations, can’t be adapted to “HD” service.

So let’s call the “HD” signals side channels, since they occupy the nearer half of each first-adjacent.

“HD” FM’s vaunted resistance to multipath depends on the redundancy of information in the two side channels. As long as one of them remains uncorrupted, the receiver can stay with the digital. And because the “space” in the spectrum between them is greater than a whole analog channel, they’re just different enough in frequency that they are unlikely to be corrupted by multipath at the same instant – and with buffering and error correction in the receiver, you might never hear a problem.

But you will hear multipath problems if one of the side channels is blocked by some other source of interference.

So what will happen if that proposed tenfold increase in “HD” side channel power is approved? Never mind first-adjacent problems. There are enough grandfathered second-adjacents in the most populous parts of the country to make trouble. Remember, two second-adjacents’ “HD” signals will only be 4 kHz apart! What kind of receiver will have that kind of selectivity?

Peter Q. George is absolutely right about this bringing about “the AM-ization of the FM band.”

My advice to “iNiquity” and its boosters ? Be careful what you wish for. You just might get it!

 

[TheBigA]

Hmmm. This sounds to me like the spacing between FMs is not as great as Congress and the FCC say it is. In other words, their approved plan for adding loads of additional LPFM stations will run head first into interference caused by their approved plan for digital radio. You can have one or the other, not both.

I wonder who'll win THAT battle. Based on what we're seeing with AM, neither.

 

[Chuck]

Hmmm. This sounds to me like the spacing between FMs is not as great as Congress and the FCC say it is. In other words, their approved plan for adding loads of additional LPFM stations will run head first into interference caused by their approved plan for digital radio. You can have one or the other, not both.

I wonder who'll win THAT battle. Based on what we're seeing with AM, neither.

Protecting second adjacents is a good idea. Protecting third adjacents (as required by 100 watt or less LPFM stations) is a waste of bandwidth. The FCC spent in excess of 2 million of your tax dollars with the Mitre Study to confirm what they already knew. Be wary when Congress decides they are qualified RF Engineers.

 

[Chuck]

Speaking to one of the engineer’s at a station running 3 HD channels here in Seattle

I brought up the topic of FMeXtra. He admitted he didn’t know to much about the system
but did say that the digital SCA stream would do nothing for multipath.

Did you have any experience with this during the testing chuck? (or anyone with field experience)
Feedback would be great!

FMeXtra allows you to specify a buffer time. For the test, we used 5 seconds. That seemed to compensate for most multipath problems, at least where we have a decent analog signal. In fringe areas, it would drop out intermittently while driving. When the car stopped, reception was rock solid. This leads me to believe that multipath is an issue, but the FMeXtra signal went at least as far as our usable analog signal. In areas where it cut in and out, only the "dedicated" would put up with our analog signal.

Just like any digital system, you either have great reception with FMeXtra, or you have nothing at all. I'm afraid that is the age we live in. Even so, I was impressed by this technology.

 

[KB1OKL]

Chuck, You basically said that FMextra's coverage was pretty much the same as you analog coverage in your experience, in what approximate percentage of a station's total usable analog signal can an HD signal be received?

 

[semoochie]

What I am saying is that FMeXtra is a technology that could be used to extend the usable coverage of HD Radio and eliminate many of its signal problems. At this stage of the game, it isn't good for much of anything else! Once in place, multiplex could be removed, restoring analog coverage to what it should be.

 

[Chuck]

Chuck, You basically said that FMextra's coverage was pretty much the same as you analog coverage in your experience, in what approximate percentage of a station's total usable analog signal can an HD signal be received?

I don't know, but it is a good question. On a full power FM station, HD coverage is pretty good until roughly your 65 dbu contour, maybe a bit further. At the current allowable 1% injection level, that would give us an HD signal of 0.74 watts ERP. That would be a little over a couple of miles radius, assuming it worked at all. Our 60 dbu contour is approximately 3.5 miles. For us, it simply would not be worth doing unless Ibiquity donated the equipment and waived the license fee.

Our analog signal is listenable on a car radio for about 10 miles. It is not a robust signal at that distance, but if someone really wants to tune in, they can. A lot of people who listen to LPFM or translator stations are DXer’s even if they don’t know it. Our analog signal works reasonably well for approximately a 7 mile radius. For comparison purposes, a seven mile radius is roughly 167 square miles. A 2 mile radius is not quite 14 square miles.

Perhaps at 10% injection, the 7.4 watts HD signal might be useful. If money were no object, (but, it is) it would be interesting to see how 10% HD worked on a low power station. On the other hand, if you allowed LPFM and translator stations to have 10% HD, you'd probably have to let everyone do it. I think that would be a problem. If the Alliance and NAB have their way, we may get a chance to find out.

 

[TheBigA]

Be wary when Congress decides they are qualified RF Engineers.

If you read the Congressional testimony, you'll see this has little to do with engineering. It's more about using an interpretation of engineering to support an agenda. That's how Congress works.