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This...I never knew!!!!!

C

Channel Surf

Guest
I have been disgusted all along by the degradation that IBOC causes to the AM and FM bands...and the over all flattening of the FM analog signal that it also creates....but the level of signal degradation that occurs.... surpised even me. Recently...I hooked up an "old school" 1980's FM AM receiver to my "old school" 1980s Yagi directional roof top FM antenna. The receiver has an analog signal strength meter. Tuning in to near by Class B FMs...that are about 30 miles away...line of sight...I was amazed at how poor the signal quality was of the FMs that also broadcast in HD...compared to their analog only counterparts. The FM stations that I was checking all broadcast from a common transmitter site. Those...that were analog only were showing up at an 8 on my meter which goes from 0-10. The FMs that also had HD would barely register a 1! Analog only Class A FMs that were a similar distance away would show up at around 4 or 5!!! Similarly....I tracked a local Class A tower that is about 15 miles from me...line of site...that is the home of three 6000 watt stations. The two stations that also broadcast in HD would barely show up at a 1. However...the analog only Class A on that tower showed up...stonger than an 8...I knew that HD was destructive to the analog signal...but I had no idea how tangible this destruction was. I suggest trying this your self if you have any doubt!!!!
 
That sounds like a problem with the radio handing the nearby sidebands or something. ???

I've been to the fringe areas of my local station's coverage areas recently and there was no discernible difference between the ones running HD and the ones not running HD. And my car radio also has a signal strength meter and I'm not seeing anything out of the ordinary between HD and analog only. Our class C's all broadcast from one of just two tower sites so comparison is easy.
 
It may be that your receiver's signal meter uses ultrasonic noise as a basis for the reading, rather than RF signal strength alone.

With a wide IF bandwidth, the digital sidebands would definitely bleed over to the analog channel and degrade the composite baseband. Older stereo FM decoder chips are especially susceptible to this form of noise, but more-recent "Walsh function" decoders and DSP usually perform better.

This is also the reason most analog modulation monitors (for example, Belar FMM/FMS series) can't be used once the HD noise generator is turned on.

Great digital radio system we have here....
 
Signal strength is not the only thing that is degraded by HD transmission. Ever since our local classical station WFMT converted to HD, high frequency sibilant sounds are distorted. I do not know the precise reason for this, but I speculate that it is due to some type of transient intermodulation distortion caused by mixing between the high frequency analog sidebands and the digital carriers; most likely occurring in the receiver IF. It is noticeable on various different FM receivers that I have used, and nobody at the station has been able to solve this problem years after the switchover (nor, apparently, do they care). If you have the opportunity to compare a true analog station to one transmitting with HD, you'll definitely hear the difference. I travel frequently to SW Michigan where I have the privilege of listening to WAUS and WSND, and both sound way better than WFMT!
 
This is an interesting discussion - I was talking with a station engineer in Dallas about it a month ago or so. He is in the camp that it doesn't affect coverage because he can't see a difference on his spectrum analyzer.

I think a lot of people forget FM is a SYSTEM which includes the user's receiver / tuner. And that may be why some people swear there is no difference while others like me see a huge coverage decrease with HD. I think the HD sidebands somehow confuse receiver / tuner AGC into shutting down the gain, thereby reducing sensitivity. The worrisome thing is that I am a DX'er that is used to re-working receivers to have narrow ceramic filters for better sensitivity. That would seem to be exactly what you would want to do to reduce the HD sideband amplitude from confusing the AGC, but it is the exact opposite. Which is counter intuitive to me. What complicates things even more is adaptive IF radios like Pioneer Supertuner 3D are the most selective and most prone to the range decrease with HD. So - narrow band - greatly affected by HD, range much less. Wide band - not as affected by HD, range about the same. Somebody figure it out, because I sure can't. But the loss in range is real, repeatable, and independent of time of day and season of the year. I know because I have a repeatable scenario, driving between Dallas and Houston. I know the ranges of stations down to the mile marker,and in several cases pre and post HD. One station has a 60 mile decrease in coverage with HD, which to me would mean a huge difference on normal radios over their normal service area. Losing the most affluent suburbs in the area, I might add. And the range restored when they shut down HD for a few weeks - then went away again once they restored HD.

Of course the observations of actual listeners - crucial to stations in past years - are ignored these days if the reports run counter to HD dogma.
 
I know that because of HD when I'm in PA i can't get the sstations that I used to get as if they were locals.
I like you have a sullective tuner with modified filters. The thing with me is that I'm close enough to the Philly transmitters that the HD would effect anolog reception.
If I can pull in an anolog signal like WPLJ, WXRK or WMGQ, the stereo is almost too noisy at best, to not even steying in stereo at worse. Mono doesn't make it much better. This is with the stereo muting defeated on the tuner.
These are stations I used to get perfectly before HD was turned on, for WMGQ i had to hit the narow butten , but still I could null out WOGL.
WPLJ i could keep it on superwide. WXRK i dont remember. There are other examples too, but those are just a few .
 
That is what got many of the old line network engineering types into trouble during the 70's and 80's when the new breed of program directors and consultants
came in, the first thing out of their mouths would be "the meters and test equipment say its all right" These PD's and counsultants didn't care what the meters and test equipment indicated.....listeners don't use it, what it sounds like is what mattered.
 
... And that's when it all went to hell. Good engineering practice was undermined by the ears and egos of PDs and consultants.


"A consultant is a guy from out of town who's out of work"......Sherm Strickhauser


-
 
Or - I always liked this one: "A consultant is a guy who uses YOUR watch to tell you what time it is. And then walks away with it."

(Isn't there ANY way we can get it LOUDER???)

(But we want to keep the quality. I don't want to hear any distortion.....)
 
In Europe, they value quality over quantity. Here in Brussels, there are dozens of great sounding signals on both AM and FM featuring many different kinds of programming in Flemish and French. No HD whine on FM or buzz on AM, and very little interference. I don't miss the rubbishy talk "shows", either.
 
audioguy said:
In Europe, they value quality over quantity. Here in Brussels, there are dozens of great sounding signals on both AM and FM featuring many different kinds of programming in Flemish and French. No HD whine on FM or buzz on AM, and very little interference. I don't miss the rubbishy talk "shows", either.
Click to expand...

I was in the South of France early last fall. I was amazed at how good some of the stations sounded. Plain old analog FM can sound really good....
 
audioguy said:
In Europe, they value quality over quantity. Here in Brussels, there are dozens of great sounding signals on both AM and FM featuring many different kinds of programming in Flemish and French. No HD whine on FM or buzz on AM, and very little interference. I don't miss the rubbishy talk "shows", either.
Click to expand...

See, I'm surprised to hear this because I've heard some recordings of stations in Germany and The Netherlands and they were so much louder than what we in the US hear off air. I thought, "Geez, people tolerate this?" I always figured the EU was overall worse with loudness than the US.
 
Europe is all over the place audio wise. Most stations sound really good, especially the state owned ones. In places like Italy, where the pirates are more common than licensed broadcasters, anything goes. I'm sure someone will chime in with more knowledge than me, but I think a lot of broadcasting in Europe is Pirate Radio. Some are well engineered, and some are not.
 
Chuck said:
Europe is all over the place audio wise. Most stations sound really good, especially the state owned ones. In places like Italy, where the pirates are more common than licensed broadcasters, anything goes. I'm sure someone will chime in with more knowledge than me, but I think a lot of broadcasting in Europe is Pirate Radio. Some are well engineered, and some are not.
Click to expand...

I second Chuck's assessment. During a trip to central Europe a few years ago, I brought my trusty analog FM Walkman (with Sony 7506 headphones) and sampled some of the local FM stations in various places I visited. One stop was in Dortmund, Germany where I happened to tune into a classical vocal recording on the public station WDR3. The quality just blew me away, it was truly comparable to a CD, maybe even better. The fact that I was near the network's local 100 kW transmitter on Langenberg didn't hurt either! (The Langenberg Transmitter site is very interesting, as you'll see if you google that term -- I hope to visit it sometime.)

Even WDR3's high bandwidth web stream sounds excellent, far superior to HD radio. If you have a fast internet connection, good speakers, and appreciate concert music, treat yourself to the 256 k MP3, here: http://www.wdr.de/wdrlive/wdrplayer/wdr3player.html

One reason many state-affiliated European FM stations sound better than those in other parts of the world is their compliance with the BS-412 standard that applies to modulation density. More about this here:

http://omniaaudio.com/downloads/whi...plug-in-for-the-itu-bs-412-multiplex-spec.pdf

I've also tuned around the congested FM band in Italy (where there are far more independent broadcasters struggling to be heard) and the quality of those stations does vary greatly. In my 2nd floor hotel room near the center of Rome, I could receive over 80 stations on the Walkman, most in stereo.
 
Look around in this site, http://radiofeeds.co.uk/ , and you'll come across a bunch of MP3 streams that are >160K. I remember I once came across a stream that was in 320K stereo (don't remember if it was on RFCU or not) and my jaw just about hit the floor, seeing that figure. I think it was one of the little independent stations in England.

320K streaming MP3. Yes, you read that correctly. Why can't people do that here?

Edit add: Here it is, it's "Leith FM", http://icecast.commedia.org.uk:8000/leithfm.mp3 . I just grabbed about a minute of the stream with wget, looked at it in my text editor and found "LAME3.97" encoder stamps all throughout! Now seriously, why can't we have that kind of perfection over here? Is there some law or conspiracy against decent stream quality?

//end of rant
 
LAME = awesome.

I'm glad to see some are using that. Our streams in the US are really ratty by comparison, especially the dreck CBS and Clear Channel force people into with their proprietary sites/apps.

MP3 is actually a poor choice for streaming, to be honest. AAC/M4A is so much more efficient at equal bitrates. A talk station I listen to from time to time runs 48 kbps AAC and MP3 feeds and the difference is night and day. One sounds like a crummy AM radio with 5 kHz audio, the other sounds like FM, with few of the swishy highs the mp3 format imparts.

We could move everything to AAC and top out at just 128 kbps and it would save tons of bandwidth without sacrificing sound quality.
 
I have occasionally picked up the BBC while DXing the AM band and the audio is FM-like, it sounds like it is modulated much less and the frequency response is wider than local stations, this on an R-390A with modified audio module and 8 Khz filter for very short periods of time.
I am also impressed by European LP's and CD's.
 
Anybody else ever notice.....there seems to be a "sound" to a new, freshly built facility?
I've noticed it many times over the years.
You hear a new station, where the audio guys, and the transmitter guys, and the antenna guys, all come in and build the thing. Everything is all tuned up to spec, and it sounds really great. Just enough compression, nice frequency response, no noticeable noise......
But, slowly over the next couple of years, it gets to sounding just like everybody else.
 
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