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Author Topic: HD (IBOC) on AM, Short Band Scan  (Read 30107 times)
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John K5PRO
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« Reply #25 on: September 24, 2007, 01:56:16 PM »

Interesting link here, to report the skywave interference to AM broadcasters. The big boyz just don't want to hear it if you tell them that so and so is being clobbered by QRM at night, when you are listening to their skywave. Heck, thats ALL we hams listen to, for the most part!

http://www.hfunderground.com/wiki/Reporting_Interference
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N0WVA
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« Reply #26 on: September 27, 2007, 09:27:07 PM »

Somebody at Ford finally noticed HD radio! Ford will start to offer a 'dealer installed option' for HD radio on all 2008 models. At least it's a start.

Mack

Start to what? Low bit-rate, high drop-out subscription radio over public airwaves? Great! sign me up!
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Bill, KD0HG
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304-TH - Workin' it


« Reply #27 on: September 27, 2007, 09:34:44 PM »

Somebody at Ford finally noticed HD radio! Ford will start to offer a 'dealer installed option' for HD radio on all 2008 models. At least it's a start.

Mack

Start to what? Low bit-rate, high drop-out subscription radio over public airwaves? Great! sign me up!

Huh?

On FM, 96K minimum bitrate, more than twice that of a CD.
Even if split into two programs, it's darn near CD quality at 48K per stereo channel. Sound quality is awesome.

AM HD sounds very, very good.

Have you ever heard an HD radio?
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Steve - WB3HUZ
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« Reply #28 on: September 27, 2007, 09:36:45 PM »

I think he means like those free subscriptions to the public airwaves given by XM and Sirrius and all the cell phone companies.
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N0WVA
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« Reply #29 on: September 27, 2007, 11:13:18 PM »

I tried to listen to an HD radio, but no one around here carries any. I really would like to hear one hooked up to a good set of speakers and compare to regular FM.

From what Ive been reading, these signals are highly compressed, and get "muddled" from all that alogarhythmic malarky. Also, the bitrate is starting around 48 bps and will probably be lower depending on how many channels the broadcaster wants to cram into the bandwidth. I like listening to FM, the music sounds pretty good and I have a critical ear. The last thing I want to hear is a warbling  watery sound.

As far as IBOC AM goes, I can just imagine what happens when you go under a high line and lose that strong signal that is needed. Once the tower pops back behind a hill, then bye-bye IBOC. Did anyone mention the 8 second delay? Im sure that will work great when listening down at the ballpark.

This is from : http://electronics.howstuffworks.com/hd-radio1.htm

HD Radio solves this problem by compressing the digital signal so more information can be sent along the same amount of radio bandwidth. Initially, iBiquity used a compression algorhythm called PAC (Perceptual Audio Coding). However, audio compressed with this method led to complaints about poor sound quality, so in 2003, iBiquity changed to HDC (High-Definition Coding), a different compression method that allowed for higher sound quality.

Although HD Radio is touted as providing CD-quality sound on the FM airwaves, the compression of the digital signal is a "lossy" method. That means that it discards some of the information in the signal, resulting in a reduction in overall fidelity to the original sound. Much of the discarded information is not perceptible to human ears, and the final product may sound very close to CD-quality, but technically it is not the same sound as on the CD.


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Steve - WB3HUZ
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« Reply #30 on: September 27, 2007, 11:31:08 PM »

Having listened to HD stations, both AM and FM, I've never heard watery audio, warbling audio, or anything approaching an 8 second delay.

CD quality is more than just bit rates and compression issues. SNR and dynamic range are just as important and NO AM or FM station will yield an SNR capable of supporting the same dynamic range as a CD. Not even close. Having listened to FM HD stations, the thing most immediately noticeable to my ear when the receiver switched from analog to HD was the big reduction in noise. From this, it would seem HD/IBOC would be far closer to CD sound than analog FM.
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2ZE
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« Reply #31 on: September 28, 2007, 10:36:25 AM »

Quote
I tried to listen to an HD radio, but no one around here carries any. I really would like to hear one hooked up to a good set of speakers and compare to regular FM.

There are many places that carry HD Radio: Best buy, circuit city, even Rat shack and Wal-mart.

As far as watery sound....
Better give a listen before you criticize. But by the sounds of things, you and all of the other so called experts have already made up your mind. All I ask is you don't poison other peoples opinion who may have not tried it yet.

As far as subscription service, the technology is there, however, even big box corporate owners dont have/want the resources to be in the subscription biz. Every station would now have to maintain/ service up to tens of thousands of accounts? I don't think so. Broadcasters will stick to what they do best, being broadcasters.
Mike, 2ZE
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Steve - WB3HUZ
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« Reply #32 on: October 28, 2007, 02:45:24 PM »

Finally got a chance to mess with the Sangean HDT-1X. This radio is WAY more sensitive than the Boston Acoustics unit -  both on AM and FM.

One FM, using the folded dipole supplied with the unit tacked to the wall of my basement, I was able to receive dozens of FM stations, easily as many as I would expect with an FM receiver with good sensitivity. I don't think I received this many FM stations with Boston Acoustics unit using an outdoor antenna! The following HD stations were received and decoded.

WHRV     89.5     Also broadcasting a second digital channel
WRVQ     94.5     Also broadcasting a second digital channel
WVKL     95.7
WKLR     96.5
WRXL     102.1    Also broadcasting a second digital channel
WMXB    103.7
WAFX     106.7

Several of the stations were a little noisy in the analog mode. The noise completely disappeared when the HD locked up. Much improved sound on all the station with more high-frequency response, less noise and better stereo separation.

On AM the sensitivity was very good. I hooked the receiver to my 75 meter dipole and was able to pull in a station on almost every channel during day light hours. Audio response was very nice, although I didn't hear a much high frequency response as I would on my SX-17 in the Broad Selectivity mode. I did not find any control to vary the bandwidth, nor did I notice any documentation of the synchronous detector. Might have to try it on some stations at night with selective fading. I was able to receive the following HD stations.

WFAN     660
WCBS     880
WRNL     910     Stereo
WRVA     1140   Stereo

This receiver locks much better on AM stations than the Boston Acoustics unit. Note in the list above, I was able to lock on two stations out of New York City about 280 miles away! There was even some fading on WCBS.

Gonna try the AM Loop antenna supplied with the unit next. I'm guessing I won't get the NYC stations during daylight hours on it.  ;-)


Ref: http://amfone.net/Amforum/index.php?topic=12092.msg88021#msg88021

The Boston Acoustics receiver is pretty deaf - on AM and FM. I also got some intermod/crossmod when I hooked it up to my 75 meter dipole. It's good to hear that some of the newer receivers are better in these areas.

I hope to test out the Sangean HDT-1X soon. It supposedly has a sync detector and variable bandwidth on the analog side, which should also be fun to play with too. Wonder why few, if any receivers had this before?
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W3LSN
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« Reply #33 on: October 28, 2007, 09:42:25 PM »

I haven't listened to the AM BCB for since before nightime IBOC got the FCC ok. A short scan of the band tonight from my locale in central MD:

WSM Nashville 650 wiped out by WFAN 660 NYC
WLW 700 Cincinatti wiped out by WOR 710 NYC
WBT 1110 Charlotte listenable, but under objectionable digital noise from 1100 WWWE Cleveland
WBBR 1130 NYC identifiable but lost under digital sidebands from station on 1120 (St. Louis?)

While I'm sympathetic to giving AM stations a crack at digital service, I think it should have been done on different spectrum. Perhaps the wasteland in the 25-27 MHz region, or higher on VHF Channel-2 when DTV cuts over in 2009. From my perspective at least half of the nighttime skywave service is now gone and the other half is polluted by digital tee-rash that makes listening unpleasant.

73, Jim
WA2AJM/3
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KB1OKL
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« Reply #34 on: November 02, 2007, 02:43:16 AM »

I lose 650 WSM regularly to WFAN, 690 to 730 is mess of hiss down here, depending on the propagation, most nights WOR 710 covers WLW 700 and WGN 720, some nights WLW covers WOR, some nights all three cover each other. 780 WBBM also blocks 770 and 790 quite a bit. When WBZ 1030 is on at night forget it that's all I hear from 1010 to 1045.  WCBS 880 also blocks 870 and 890. There are some others that hiss up the band here also. At the bottom of this post is a link to a list of iBlock stations on both day and night. The list is not growing very fast in fact it shrank recently when Citadel shut it off due to consumer complaints.

Here's a column about Ford's new iBlock offer:

http://gormanmediablog.blogspot.com/2007/10/blog-post.html

here's something about when Citadel shut of their iBlock and why

http://www.orbitcast.com/archives/abc-citadel-suspends-am-iboc.html

here's all aM iBlock stations on the air, this is constantly updated:

http://topazdesigns.com/iboc/station-list.html
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