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 Post subject: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Fri 02, 2018 7:33 pm 
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Location: Memphis, TN
I've noticed a weird issue on different radios when tuned to the same local station. This station simulcasts an FM country music station and tends to play a lot of 'real' country music instead of the new 'tractor rap' garbage that seems to pass for music. Needless to say, I listen to it a lot.

The problem I've noticed off and on though is that I can hear the guitars go out of tune every now and then, sounding exactly like the musician slid his finger one fret low... I know the song, and play a little bass myself, so it's definitely not supposed to sound like that. It's not constant, but happens several times per song, and might do that for multiple songs, and then won't do it for several hours, or even days. It also does this on different radios, so I'm led to believe the problem is at the station and not on my end.

What would cause this? I have a feeling I'm getting ready to go down the audio processing/transmitting rabbit hole.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Fri 02, 2018 8:34 pm 
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You say it is simulcasting. Can you get both the simulcast and the source at the same time to compare? Or maybe listen online and compare to OTA? I am not sure what options stations have for processing content besides compression and limiting. Perhaps there is also some sort of time compression going on sometimes. I have heard they have ways to reduce gaps in speech to fill more words per segment. And said to be practically inaudible but might affect music if they used that? Try the comparison.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Fri 02, 2018 11:30 pm 
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Location: Near Brandon, Iowa
I don't know what sort of medium the offending station uses to drive its transmitter: platter, analog tape, digital- but if it's one of first two, the turntable or deck may need servicing. If the station uses a digital audio source, the broadcast engineer is able to tweak this audio stream so maybe the jocks are "tuning" the sound stream to match their visions of pitch perfection.

Can't say that I've ever encountered that particular problem; but around this area, a local "oldies" AM station plays great-sounding songs interspersed with horrendously garbled voice commercials. It's like this on every radio I own. This has been going on for years; on the companion FM station (which plays exactly the same content) this problem doesn't exist. The only thing that I can think of is that the AM engineer is boosting the volume on the commercials, possibly to draw more attention to them.

Nothing that a little more bourbon can't cure...


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 3:05 am 
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Location: Milwaukee,WI
If it happens often enough it would be great if you could make a recording so we know what you're hearing.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 3:38 am 
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The best way to resolve the issue is to send a recording and a letter via email to the station involved. Tell them it happens on all of your radios. Their engineer, if they actually have one, will hopefully recognize the problem.

Dave


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 6:26 am 
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Location: Sunnyvale CA
Dave Doughty wrote:
The best way to resolve the issue is to send a recording and a letter via email to the station involved. Tell them it happens on all of your radios. Their engineer, if they actually have one, will hopefully recognize the problem.


I think you have put your finger on the likely problem with this plan very nicely.

Brett


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 10:25 am 
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Location: Rochester, NY.
If there is an engineer, he may be overwhelmed or not care either.
I noticed an AM sister-station rebroadcast of an FM stereo station had only one channel of the stereo signal being used. It may have been the Left channel feed while the Right channel wasn't used for the AM monaural audio stream. It would seem that combining the L+R audio wouldn't be that difficult.
I brought it to their attention, they noted it but they didn't seem to care.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 10:36 am 
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Location: Ft Worth TX
"Statistically" they have no more than one-eighth of an engineer.

If it goes a whole fret flat while the tempo does not alter, sounds like an artifact of digital storage/retrieval/shipping & handling. Brother still in the biz, sez NObody uses mechanical content any more. More like, the (dreaded) "cloud". And [the sky guy] knows what all along the way to your oracles (sic).

Or the whole thing could be running on Windows.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 9:23 pm 
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Location: Milwaukee,WI
The reason I would like to hear a recording of the issue is because I have a hard time understanding why just the guitar would sound out of tune. I would think the whole song itself would change pitch. How could a guitar buried in the mix of instruments actually get singled out in a "digital artifact"?


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sat 03, 2018 9:57 pm 
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arbilab wrote:
"Statistically" they have no more than one-eighth of an engineer.

If it goes a whole fret flat while the tempo does not alter, sounds like an artifact of digital storage/retrieval/shipping & handling.


I agree, this is likely to be a function of digital dynamic range compression.

Brett


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sun 04, 2018 3:20 am 
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Or maybe using the internet with cheap digital converters subject to latency 'wowing', or a cheap internet pipe using buffers to 'improve' the rate instead of a real STL system.

Not that an internet-based studio-transmitter link can't work very well, it just isn't cheap.

Dennis

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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Sun 04, 2018 6:12 pm 
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Dave Doughty wrote:
The best way to resolve the issue is to send a recording and a letter via email to the station involved.

That may not help, as it may not find its way to the station's Chief Engineer, and even if it does he may not know or care. As suggested upstream, posting a recording or link to a recording here might help. I've been dealing with broadcast automation systems for nearly thirty years and with broadcast engineering for nearly fifty.

Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Mon 05, 2018 3:41 am 
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Location: Memphis, TN
- I can try to get the FM signal, but I don't have any operable FM radios at the moment. Plenty of AM radios though. :lol:

- I'll try to get a recording of it, but the problem is that it's HIGHLY variable as to when it occurs. For example, it hasn't done it once today that I've heard, but other days I've heard it on two different radios only a few minutes apart when I was working on one. It does seem to occur during the daytime more often though.

- The tempo of the whole song doesn't seem to change, but just the pitch of the guitar on higher notes. For those of you who play, think of bending the strings, but in reverse...

- So some of you are thinking it may be a corrupt data file, essentially the digital version of a scratched CD?

- Along those same lines, I've heard some songs on FM in my truck that sound fine, but it REALLY seems like they're playing faster than my copy of the same song I bought on iTunes. I've read that 'back in the day' stations used to speed up the turntables a little so they could fit more in an hour. I'd imagine with computers, the same thing could be done without the pitch shift, so perhaps it's a glitch with that?

- I'll email them the next time I hear it and name the song I heard it on.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Mon 05, 2018 10:32 am 
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Location: Ft Worth TX
Quote:
I'd imagine...
Don't watch much cable? A LOT gets sped up. Everything from Star Wars to Desi Arnaz singing. The pitch does not change but the pacing goes so far off it's distracting.

Not thinking of a way it's electronically AND accidentally possible to flatten a single instrument out of an MP3 mix. Your ears however, can. As I recall from sensory psychology 303 50yrs ago though, louder sounds tend toward perceived sharpness. ...(?)...


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Mon 05, 2018 12:52 pm 
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I absolutely hate when a song is sped up.

If the speed is the least bit fast I notice it immediately.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Mon 05, 2018 1:33 pm 
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You need to monitor the AM and FM simultaneously to know if the AM is simulcasting the FM live or not. The only practical reason I can think of for time stretching the AM feed is if they run different commercials or promos on the AM at each stop set and those times are somehow different. Unless its a mom and pop station locked in the 90s using 30 year old cart decks most every station today uses a computer based system for media which is easy to alter and time stretch. Only other thing I can think of is if they have a processor in the chain that adds width and depth to the stereo image and the AM is picking off a delayed artifact somehow. Either way they probably dont care because the AM side isn't a big revenue generator compared to the FM with a simulcast.

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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Mon 05, 2018 3:38 pm 
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jack.estes wrote:
- So some of you are thinking it may be a corrupt data file, essentially the digital version of a scratched CD?

That is possible, but you didn't say that it is always the same place in the same song. If it occurs in multiple songs file corruption is less likely as a cause. I am thinking it is a likely a problem in the automation system that sometimes messes up the D-to-A process. My second and third candidates are a problem in a digital STL and a processor problem. It would help a great deal to know which station this is so that I can look at some technical information about the station on the FCC site.

Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Mon 05, 2018 3:44 pm 
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arbilab wrote:
Not thinking of a way it's electronically AND accidentally possible to flatten a single instrument out of an MP3 mix.

The vast majority of commercial radio stations do not play MP3s of music. With possible multiple stages of digital compression and decompression an MP3 can quickly sound very bad. Commercial stations want to start with optimum quality and that means WAV files. Besides, stations are not trying to cram as many tunes as possible into an iPod, everything is on a hard drive and today's hard drive are large and relatively inexpensive.

Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Tue 06, 2018 6:24 am 
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Location: Ft Worth TX
Thanks Dale. Most I know digital audio chains is that there are some and they can be ANYthing. Out of the BC biz before that reached practicality.


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 Post subject: Re: AM broadcast station going 'flat' on high notes?
PostPosted: Mar Tue 06, 2018 8:05 am 
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Joined: Oct Thu 02, 2014 5:57 am
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Location: Memphis, TN
Dale,

The AM station is WOWW at 1430 in Germantown, TN. The actual transmitter is technically in Bartlett, TN, near Shelby Farms park. The local air traffic controllers call that area the 'antenna farm' for good reason. The 'original' broadcast is WEBL 95.3 FM in Coldwater, MS. https://radio-locator.com/info/WOWW-AM

I'm in the shop now, and I haven't heard any issues this evening, so that pretty well shoots the recording possibility in the foot for tonight...

When you refer to the D to A process, am I correct in thinking that you're referring to a Digital to Audio process?


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