Monday, December 04, 2006

Yet more Radio Shack and HD Radio

Just a quick one this time...this weekend I discovered my local Radio Shack now has an Accurian model HD Radio on display sitting next to the Boston Acoustics Receptor HD model. Even though they had the rabbit ears antenna I helped them hook up still attached to the Receptor HD, the Accurian had NO antenna connected to the FM co-ax jack and a twisted loop of speaker wire (what the hell?) attached to the leads for the AM antenna.

Not surprisingly, there was zero HD reception on the AM band, and even after I popped on the rabbit ears there wasn't very good FM reception either. At least some FM stations came in on HD, though...I put the rabbit ears on the Accurian and left it tuned to WBOS HD2 since they were playing an Everything But the Girl song I liked.

2 comments:

700WLW said...

HD Radio is a fraud and a failure - the big HD Radio Rollout has been a complete joke. The public is totally apathetic about HD Radio and HD radio sales have been anemic. HD Radio/IBOC causes adjacent-channel interference and has only 60% the coverage of analog.

Aaron Read said...

I'd rather not get into a "He said, She said" about IBOC, but I would like to expand a bit on your comments...

Public apathy is a bad thing, I agree...but IBOC has always been intended to be an evolutionary process, rather than a revolutionary one like satellite radio. In other words, it was known from the outset that it would take 10-20 years (at least) to get significant market penetration; most people would not seek out an HD Radio, they would seek out a radio and eventually find nothing but HD Radio-equipped radios for sale.

Sales have been anemic because there's only been a handful of radios and they've been at a "first adopter" premium. OTOH, prices have dropped by almost 50% in one year. We'll see how well/badly sales are doing by next Christmas.

The 60% coverage number you cite is essentially false because "coverage" is a meaningless term without context. The FCC defines coverage as being out to the 60dBu "protected" contour for 50 percent of the population, 50% of the time (the 50,50 ratio). The FCC has made great pains to remind stations for DECADES that they cannot rely on coverage beyond the 60dBu, and yet stations foolishly have. Much to their dismay when another adjacent station expanded to fill an area up to the contour and wiped out the coverage beyond the 60dBu. Most HD Radio installations are currently making at least the 65dBu, and they should be reaching the 60 or 55dBu contour. Why they're not is often due to small problems in the transmission system that were "masked" when using 20000 watts analog but become more apparent when using only 200 watts digital. It's a new system and stations are still learning as they go, too.

Quality of the signal reception is worth pointing out, too. I don't mean audio fidelity...that's a whole 'nother bugaboo and I freely admit that HDC isn't the greatest audio codec for every type of programming. No, I mean how clean a signal are you hearing when you listen to analog? Usually by the time you get out to the 60dBu the signal is struggling against adjacent channel interference, multipath, and terrain shielding dropouts. With HD Radio those problems are just GONE. With HD Radio, the signal fidelity is exactly the same throughout the entire digital coverage area; that's a benefit easily overlooked until you go back to analog and hear all the static, pops, and "picket fencing".

As for adjacent-channel interference, on AM this is definitely true...and the nighttime skywave problem is a problem. Based on the engineering I've seen, though, it's mostly a problem for DX'ers and for about 5% of all the AM stations out there. Especially those highly directional AM's that have been shoehorned in over the last 15 years. For the remaining 95% the aforementioned improvement in signal quality throughout the protected service contour vastly makes up for it. Radio World: Engineering Extra had a great article about how much WBUR-AM's coverage improved with HD Radio.

Yes, it comes at the cost of long range "DX" listening. So what? The FCC hasn't cared about DX'ing since the CONELRAD days over 40 years ago...it's all about LOCAL service; not listening to WBZ from Boston while you're in Georgia.

There is also 1st adjacent interference on FM but it's a lot less noticeable; you've gotta be pretty close in to the transmitter (within a few miles even on the Class B's) to hear the "white noise" of IBOC carriers on adjacent channels. For the commercial band, the FM spacing rules mean that by definition within a few miles there isn't going to be a competing signal. For non-comm's, well, usually the power's lower to begin with. In those few cases where a small station is shoehorned next to a bigger one running IBOC, that does suck.

But ultimately it's irrelevant...the simple cure for it on FM is to start broadcasting in HD Radio yourself; the upper and lower IBOC carriers are nearly 100% redundant, and can easily survive one adjacent channel's interference with little or no noticeable change to a listener using an HD Radio tuner.

Does that mean the FCC insidiously wants all stations to upgrade to HD Radio? Well, yes! That's the point! Eventually all stations are supposed to be digital and the analog signals turned off; that will afford substantially increased data bandwidth on digital for additional services like on-demand files, video and more. So the FCC (and everyone else) has a vested interest in getting everyone to broadcast in HD Radio as soon as they can. They don't want to mandate it like DTV precisely because of the giant clusterf**k the mandated DTV transition has been...but the FCC is not above letting the system encourage you to migrate on its own.