Nighttime AM HD: It works… kinda - WABC-HD New York | September 17, 2007
After trying for 3 days straight, I was finally able to record a very short AM HD clip of 77 WABC-HD New York, Monday night 9/17/07. It decoded for about one minute before the signal dropped back down below the HD threshold.
Listen and judge for yourself. Is this a workable system, allowing AM stations to broadcast their HD signals at night? Reports of severe digital interference to first adjacent signals are widespread, so if HD can’t be reliably decoded by the few available receivers, is this even a good idea?
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I haven’t noticed a degredation in dxing so I have no idea what people are talking about. I think most of it is bunk, just to slam on HD radio.
I’m not sure how well it works, I need to listen to much more to make a determination. I don’t have an HD radio anyways so the point is moot as of now but one potential problem exists. If you do some HD radio (or even HDTV) DXing, you still have to receive the whole signal, it is either there are not and if it fades out, you lose the entire thing. At least with analogue radio and TV, you can make out the audio (and picture with TV) even if there is some interference. If you get interference with a digital signal, again, you lose the entire signal.
Guys, I think people have to understand the nature of the technology. As far as DX’ing goes, with AM/FM its not going to matter much, except for the adjacent channel digital noise from HD signals. The DX lists are filled with comments from hobbyists who are angry that weak signals are now very difficult to pick up.
Of course, from an industry standard, they don’t care. Why should they? Station owners do not want listeners tuning into stations ouside their home market. On the other hand, it is to their advantage to have both a clean signal and an HD signal that can be decoded by current receiver technology easily. FM HD works fairly well as long as the HD signal is strong enough and there’s a good line of sight between TX and RX. AM is a different story. I can’t speak for the other receivers, such as Radiosophy (which I’ve heard is head and shoulders better than anything else on the market), but the Boston Acoustics Recepter is nearly worthless for picking up AM HD. It simply has a very poor front end which is absolutely lousy for trying to hear weak signals. The FM side could be more sensitive also, but it’s much better.
To the subject at hand. The technology works just as any other digital decoder works. An HD reciever must be able to decode a digital burst (theoretically measured in nanoseconds) and convert it to something that can be reproduced in audio circuitry(sp). If there’s an error in the stream, the whole packet is rejected and you get silence. In the case of a CD, you get a skip. So, as Charles said, it’s all or nothing, and a weak signal, attenuated by weather, buildings or even foliage, is virtually useless for HD listening. With AM HD, its a little different with respect to signal degradation, because of the nature of radio waves at lower AM broadcast frequencies. Signals travelling over water or highly conductive parts of the U.S. are decoded better than those over rocky terrain, inside of buildings near computers, or during Summertime weather conditions where thuderstorms disrupt radio signals to a great extent.
Hope that gives you all some insight
The degradation in the fidelity of the analog signal just to accommodate the bandwidth requirements of HD signals is enough reason to hate HD radio. The frequency response in analog has been almost halved plus even in a strong signal area, you get ubiquitous pink noise under the signal courtesy of the digital carrier.
There also was a time when sales departments were smart enough to know how to sell whatever market their station happened to attract rather than trying to customize their audience to meet their clients’ expectations.
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