HD radio – Page 12 – Engineering Radio

Digital Radio Mondiale, an alternative to HD radio?

Could be. Digital Radio Mondiale, or DRM, is a modulation scheme that a group of broadcasters and transmitter manufacturers have been working on since about 1997 or so. There are numerous shortwave broadcasters; the BBC, the CBC, Deutsche Welle, Radio France Internationale, the VOA, and others have been using DRM on shortwave for several years now. I can state that the shortwave DRM system works well, I have a software decoder and use the sound card input on my computer to decode and listen to DRM shortwave broadcasts.

The goal of DRM is to establish a worldwide open standard for digital broadcasting in the LF, MF, HF, and VHF bands. In the early years of development, DRM was designed for digital broadcasting on bands below 30 MHz. This system is now known as DRM30. Since then, the DRM consortium has expanded that to the VHF band (up to 174 MHz) as well (meaning where the current FM band is located) and has called that system DRM+.

DRM uses COFDM (Coded Orthogonal Frequency Division Multiplex) modulation, which is the same as IBOC HD radio^TM. This is a robust modulation system that employs multiple carriers at lower power (than an analog carrier) spread across the entire allotted bandwidth.

One of the claims is DRM transmits less power and is more energy efficient. In general, digital radio modulation does transmit less power, that is true. However, transmitters have to be run more linearly for digital due to the increased bandwidth. This may not translate to greatly increased efficiency from the AC mains to RF standpoint. Because of that, there is more waste heat, and thus more air conditioning is needed to cool the transmitter room.

Some of the advantages of DRM over Ibiquity’s HD radio^TM are:

Open source system. Royalties are paid by the transmitter manufacturers only (and to date, most major US transmitter manufacturers have already paid these). There is no royalties paid by the broadcaster to install DRM or by the consumer when purchasing a DRM-capable receiver. One company does not own the rights to the modulation system for all the broadcasters in the country.
Universally standard; accepted by the European Telecommunications Standards Institute (ETSI), International Electrotechnical Committee (IEC), and the International Telecommunications Union (ITU).
The CODEC is HE-AAC 4, which is widely used worldwide.
DRM30 and DRM+ fit into existing band plans and will not interfere with other users on adjacent channels. DRM30 is designed for 9 KHz channel spacing and DRM+ is designed for 100 kHz channel spacing, all of which comply with existing FCC regulations.
Standardized receiver profiles are things that must be included in all DRM receivers. There are several advanced options as well, such as a media-rich system that includes video.
DRM+ has several added features: DRM text, which is similar to RBDS. EPG or electronic programming guide, which shows what is coming up next and a searchable schedule of when programs may be heard out to seven days. Some DRM+ receivers will have a TIVO-like recording device that allows the user to record programs and playback later.
Traffic reporting and routing

In addition to that, DRM30 stations have the ability to transmit low frame rate H. 264 video. This is a distinct advantage for short-wave stations that are seeking a way around firewall blocking. The video image is small, 176 x 144 pixels and it is 8 frames per second, which is about as good as can be expected using a 9 KHz channel.

In some cases, DRM is capable of a hybrid mode (ed note: DRM calls this “Simulcast mode”), but what have we learned about hybrid mode digital radio: It doesn’t work very well. In short, it would be better if DRM were employed in the digital-only mode. To many, this is a distinct disadvantage, but I don’t see it that way. There have been many that have made the IBOC rollout/FM broadcasting rollout analogy. Frankly, those arguments don’t hold water. When FM was introduced, no attempt was made to shoehorn it into the existing AM (Standard Broadcast) band, it was not designed to interfere with other stations or itself, power levels were sufficient for good reception using existing technology, quality over AM was markedly improved and programming was often separate (simulcasting with existing AMs did not start until later). My point here is that any digital broadcasting should be introduced on a separate set of frequencies. Some have proposed using TV channels 5 and 6, which makes some good sense. Whatever the outcome is, we have learned, the hard and expensive way, that hybrid digital broadcasting does not work well.

A brief video about DRM30.

Currently, DRM30 is only allowed on shortwave broadcast frequencies in the US. I asked a product development engineer from a major reputable broadcast transmitter manufacturer about this, and his response was:

Medium-wave broadcasting in the US already has HD radio, so the FCC would be disinclined to allow a new standard
One might be able to apply for an experimental license to broadcast DRM, but it would likely have an expiration date
It is possible to operate DRM in a hybrid mode on the AM band and occupy the same bandwidth as HD radio^TM (30 kHz), it might also be possible to squeeze that down to 20 KHz.
Most modern (read: solid-state) AM broadcast transmitters should be able to transmit DRM without modification (antenna systems may be a different matter).

It might be fun to apply for an experimental license to broadcast somewhere in the 1600-1700 KHz range with DRM30 only and no analog modulation, except for an hourly station ID in Morse. A 1/4-wave tower in the middle of that band would be 141 feet tall. With the use of a skirt, a grounded tower can be employed. That and a few above-ground radials and the system would likely be pretty efficient. Part of the experiment would include driving around and taking signal strength readings while recording the programming material. This would give some real-world testing on how the system would perform in widespread use.

Of course, this would require a major about-face by the FCC, which is not likely unless someone there grows or somehow acquires a backbone.

Some people question the need to do any type of digital broadcasting. I am a realist, in one way, shape, or form, digital radio broadcasting will (or already is) take(ing) place. It would make the most sense if the best system were used, which is not necessarily the first system proposed. The big question is, will today’s terrestrial broadcasters be involved, or out of business?

History repeats itself?

Letter to the editor in the April 15, 1987, Radio World:

I’ve heard all the garbage I can stand about the AM stereo “issue.” The problem?

1. Motorola and Kahn each was a monopoly.

2. The stations don’t want to waste $6,000 on the wrong system.

3. The FCC is afraid it will be sued by the “sore loser” in a standard decision.

4. The receiver makers are afraid of wasting millions of the wrong system.

5. The listeners don’t know anything about AM stereo.

Does any of this sound vaguely familiar regarding some AM “improvement” schemes currently being used? Those that fail to learn from history are destined to repeat it, Bob.

IBOC update, part II

In a way that never ceases to amaze me, Bob Strubel spins another yarn about HD Radio.™ According to Bob:

Tom’s experiences at the Ford dealership are disappointing. We believe they reflect the growing pains which often occur when companies launch new technologies. Tom hit the lot as factory installed HD Radio receivers were just launching.

Well, then, I guess that explains that. If I went to a Ford dealership today, I’d find plenty of models with HD radio(s)™ stock, right?

As far as new technology and growing pains, let us pick that apart piece by piece:

IBOC has been in development since 1990 or thereabouts. Not really new technology. Apple’s iPhone and iPad are new technology (2 years and 3 months respectively).
Ford Motor Company has been an HD Radio™ partner since 2007. One would think that all the kinks would be worked out by now.
The IBOC rollout hit a wall around 2008 and hasn’t grown since then, both the AM technology, which appears to be shrinking, and the FM technology, which appears to be subsidized by the US government.

To test Mr. Strubel’s next statement:

Had he been able to hold out with his old Explorer for another couple months, he would have been able to purchase an Escape with a factory installed HD Radio receiver as these vehicles hit dealerships the first week of August.

It is now the third week in August, I stopped by three Ford dealerships in reasonable-sized cities around here. Not really wanting to waste a salesperson’s time, I cut to the chase and asked about vehicles with HD radios. Here is the response:

Dealership #1 said they knew about HD radio, but none were in any of their stock vehicles. They also could not give me an idea of how long I’d have to wait to receive one if ordered separately.
Dealership #2 pointed me in the direction of SiriusXM, saying that satellite radio was digital radio, or HD Radio™, or whatever it was
Dealership #3 never heard of HD Radio™ and said that all their radios were digital (Like, Duh!)

Finally, there is this standard iBiquity statement that seems to go well in any situation:

…it’s ironic that his negative experience happened at a time when the consumer rollout of HD Radio Technology is stronger than it has ever been. We are seeing dramatic receiver sales increases across all segments – OEM auto, consumer electronics, and the new portable HD Radio category. Overall sales of HD Radio receivers will more than double in 2010, and that is on top of a doubling from 2008 to 2009. Can anyone point to any other facet of AM/FM that has seen this sort of growth over the last several years?

Sure, analog AM and FM receivers continue to fly off the shelves in all the markets quoted above too. Furthermore, doubling receiver sales from one small number to another small number is not that dramatic. As Mark Twain said: “There are three kinds of lies; lies, damned lies, and statistics.” It’s like the rookie batting 1000 after his first time at bat; it happens occasionally, it is really not that dramatic or remarkable.

Comparing new technology such as the iPad to middle-aged technology such as IBOC is silly. The iPad has all sorts of neat features, interactive programs, applications, etc. IBOC is just a one-way radio that does sound any better than the old-style radios.

IBOC update

Harris Dexstar exciter — Harris Dexstar Exciter

I was reading several very interesting IBOC-related articles and posts today. First of all, if Tom Ray, an engineer from WOR and a strong proponent of AM HD Radio seems a little reticent lately, well, perhaps this explains a few things:

Tom Ray finds himself discouraged based on a Ford shopping experience.

I’d recommend reading the whole thing, however, here are some of the highlights:

Fear of HD radio going the way of FM Quad and AM Stereo
Asks for an HD radio at the Ford dealership, no one can figure out what HD radio is
WOR news director states “HD radio sucks” then asks to have his car radio programmed for analog-only
HD radio less known than Apple iPad product
Joe consumer would not be able to make heads or tails out of it.

RBR has more here.

It is telling that one of the most vocal proponents of IBOC would publish an article such as this. It seems to be diametrically opposed to the latest press release from iBiquity insisting all is well, never fear, etc. Perhaps it is meant to spur things on, rally the troops as it were.

The second item I found very interesting, Paul Riismandel from Radio Survivor fools around with a Sony XDRF1 HD receiver. He posts a great deal of information about his experience. It is a good read. To summarize some of the points of this story:

It is difficult to receive HD radio signals in the Chicago Suburbs.
When FM HD radio is in use, it is difficult to tell the difference in sound quality between analog and the IBOC programming
Secondary channels have low bit rates and are not suitable for listening to music

Finally, Radio World, again, states that after six months 86 FM stations have completed the allowed IBOC power upgrade. That information is from the NAB. I cannot find any official FCC information regarding this, I would like to know if any of those 86 stations are around here. By the way, 86 out of 1,524 stations representing 6 percent of existing IBOC stations have been upgraded. That makes 0.9 percent of the total number of FM stations licensed to the US running -14dBc IBOC carriers.

I will allow the reader to draw his/her own conclusions.