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Audio issues at area AM station

tomservo

tomservo

Okay, I've got a challenge for the engineers out there.

There's an AM station in the next town that has some audio problems and I'm wondering if you fine folks can decipher what is wrong at this place, because I've never heard any station like it.

I don't have any audio (yet), but the best way to describe the sound is "a complete lack of bass". The audio spectrum seems to begin anywhere from 1 to 4 kHz and it goes all the way up (and possibly past) 9/10 kHz.

It also sounds like there's no processing, and the audio levels are much lower than other area stations. That part I understand but the lack of bass is a mystery to me.

I'm no engineer but I'd love to hear ideas of what might be askew at this operation to cause those kinds of issues. I'm pretty sure the transmitter plant is pre-1980. The building and three towers look like originals from the 40's.

On most average (bad) car stereos, the high end distorts terribly on much of the blues and gospel music they play, making it unlistenable. It wasn't until I fired up an AMAX AM stereo tuner there that I heard just how much high end they have.

I'm not associated with this operation and have never contacted anyone w/r/t the situation, but I might if anyone can come up with some good guesses as to what's wrong. And I'll try to snag a recording of it next time I'm in the area.
 
Are they locally programmed? If they are on a phone line, there may just be a bad connection on one side of the audio pair. If it's a phone line, you might also hear lots of hum, though.

If it's a satellite feed, same issue with the balanced audio, but maybe no hum involved, since the line is shorter.

If it's really old equipment, bad coupling caps in the audio path (of almost any piece of gear) can cause problems with low-end response.

They might be raising the audio modulation levels in to the region of overmod/distortion, trying to hear some low end. Maybe they don't have a good receiver.
 
Depending on the method of modulation used by the transmitter, there are workarounds for a sick modulator section that might produce this sort of sound. Anything like that would normally be quite temporary until parts arrive, for instance.

The high side of your "low" frequency response estimate would render the station pretty much unintelligible, though.
 
The station's 100% local. There was a day several months ago when I happened to be going by the TX site and was listening. They were on auto pilot with no IDs or commercials. A phone company truck was in the driveway, so perhaps they were doing some work. The audio was the same, so I'm inclined to rule out a phone line... But I never did consider that option.

I've lived in this area for two years and in that time, the audio's either been messed up or they've been off the air. Station's been on consistently after new owners came in, but they haven't done anything about the audio. It's a shame, because it's a good mix of local talk and Mississippi blues music.

If I get down that way in the next day or two, I'll try to snag a recording of it.
 
Is the station simulcasting audio from another station?

A friend of mine just purchased a station that had been spun off from a small group of area stations. It had been simulcasting the audio from another station in the group.

I was told that the previous owner was feeding a 3k pots line directly into the 1950's transmitter with no audio line at all. No need for a peak limiter...it never got over 40%. The audio sounded like it was comming through a garden hose... if you could hear it.

My friend junked everything except the tower.
 
There's no simulcasting going on, it's all local as far as I can tell.

Here's a 30 second audio sample (mp3, 690kb). I looked at the audio with a sonogram tool in my audio program and it does show content well below 1 kHz... Looks like I was waaay off on that guess. There seems to be a roll off down near 125 Hz as best I can tell. And after hearing some speech (not in the recording) it is obvious they are at least using some sort of limiter in the chain.

There's not the kind of distortion in that sample that I normally hear since I used the widest AM radio I could find to make the recording.
 
Zach said:
Here's a 30 second audio sample (mp3, 690kb). I looked at the audio with a sonogram tool in my audio program and it does show content well below 1 kHz... Looks like I was waaay off on that guess. There seems to be a roll off down near 125 Hz as best I can tell.
Click to expand...

I downloaded the sample and examined it using Adobe Audition. Yes, the audio does nose-dive from 125 Hz and below. I found the highest level of audio at about 600 and second highest at 340 or so. I normally expect the something around 340 to 370 to be the highest and for everything above 600 or 700 to really start down hill. There is a little bit of fall-off but for all practical purposes it almost remains level out to 2,500 and then begin a very, very gentle reduction in signal all the way to 8,000 after which the signal "falls off the earth".

What I found interesting was if I used filters to bring the lower frequencies up (which I expected to also bring up the low frequency noise) there just wasn't any low frequency that could be brought up.

Someone else is going to have to be the expert ears to guess how much of this is having an inappropriate audio processor in the chain, and how much is just worn-out exhausted and busted transmitter and audio chain.
 
In the 1980's, for several years 1090 XEPRS (50kw) Rosarito Beach, BCN, Mexico sounded very tinny. A CE at another station told me the modulation transformer was bad. I visited the transmitter site in 1980. The rig was old, from the 1940's. I can't remember the brand. The mod monitor was pinned. Obviously the qudio was distorted as well as tinny.
 
Had a CRL AM-4 system that had been sitting around for a few years sound like that. Shot gunning all the capacitors fixed it good as new and it's still playing somewhere in MI.
 
I appreciate everyone's take on this station. I'm always interested in good processing, even if it's on a lowly unrated market AM station. One of these days I may get up the courage to just stop in and say hi and see if I can talk to an engineer. If one even exists. The same people who run this outlet have an FM that almost constantly has AC hum behind the music. So maybe no one's paying attention and no one cars. :-[
 
Zach said:
I appreciate everyone's take on this station. I'm always interested in good processing, even if it's on a lowly unrated market AM station. One of these days I may get up the courage to just stop in and say hi and see if I can talk to an engineer. If one even exists. The same people who run this outlet have an FM that almost constantly has AC hum behind the music. So maybe no one's paying attention and no one cars. :-[
Click to expand...

Welcome to radio in the 21st century. A lot of engineers have left the business and the ones that remain are over worked and under supported. Sometimes a facility can't get an engineer because they've failed to pay someone before and no one will take that chance again.
 
I bet they haven't had a enginner there in years. Something tells me they are just limping along with no new (to them) equipment and no one qualified to fix what the own. The sad thing is this kin of operation is becoming ever more commonplace in smaller markets. The FCC is a paperwork tiger. In most cases they have no technical experience to draw on themselves. Broken stuff stays broken and no one cares but heaven forbid a guy doesn't log another station's missed EAS or forgot to log "Quarterly tower report" when neccesary. It all comes down to the FCC being a joke. (and a bad one at that)
 
I think most of us have heard the old saw about how some small-market stations will hire a young, energetic engineer, who will get busy and fix everything. Then, they declare him "unnecessary, since everything is working", and let the place fall apart again, until the next guy comes along.
 
These days there are stations out there that don't even bother with the energetic younger engineer... They think of their station like a washing machine. The only time they call someone is when it totally breaks down and creates a mess. Then they want help like yesterday and at very little cost. The good news is that there are fewer of us out there to do the work so those that think decent engineering grows on trees are quickly learning it doesn't work that way. My guess is this little station may fall in the catagory of "if it's on we don't care". Sadly the FCC won't do much about it anytime soon, if ever.
 
OKCRadioGuy said:
My guess is this little station may fall in the catagory of "if it's on we don't care". Sadly the FCC won't do much about it anytime soon, if ever.
Click to expand...

More beancounter-driven radio, I guess. :-[

The region seems to suffer from quite a bit of "if it's on we don't care". There's usually two or three FMs in the same community with a constant 60 Hz hum in the audio and one I just heard today with — get this — a flutter problem. Chalk up another audio anomaly that I've never heard before. It sounds like all the audio is coming off a turntable that's got a case of the butterflies. Subtle but noticeable.
 
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