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FM stations audio, lowest and highest

B

Big 121

Trusty sound level meter in hand, I scanned the band, checking levels..
Because of the high levels of bass boost stations are using,and my cars response goin' down to the 30hz range, I measured in db(a) with averaging on, tone controls"flat".
Lowest= #1- Q96 0% audio)
Highest= #4- 91X, KGB (tie)
#3- Walrus
#2- 93.3
#1- 90.3, 92.5(tie)
Assuming KGB/93.3 are hitting max legal limit, then the top 2 are quite overmodulated...but not by Mexico's
standards. So, yes, there is a level difference that your ears are hearing.

Big 121
 
Whoa dude. This means what? Did you look at anything on a mod monitor to see how much (or little) dynamic range there is on these stations? I'm also a little confused about your comment about KGB/93.3 hitting the max legal limit, but you refer to 91X being in a tie with KGB. So is there a top two between the #4 tie, or is the #1 tie 90.3 and 92.5?

Despite Victor Diaz' historic comments of maybe Mexican watts are different, the fact is 75kHz modulation is the same no matter where you are. Did you look at an occupied bandwidth paint on a spectrum analyzer? You made this measurement with a handheld sound level meter in your car? What was the road noise factor? Were you mobile in Mission Valley or parked on top of Soledad? Is your meter flat and recently calibrated? Are your car speakers flat?

A-weighting is only really valid for relatively quiet sounds and for pure tones as it is based on the 40-phon Fletcher-Munson curves which represented an early determination of the equal-loudness contour for human hearing.

I have to question your results on a number of levels, but it seems mostly you're trying to say that Mexico based stations are cheating. I could believe that, but not based on the presented evidence. Saying you assume two American stations are hitting the max legal limit without something to back that up is kind of making assumptions. Maybe they're running less agressive processing or even under modulating. Comments like this need to be backed by better engineering science.
 
It's casual "test" of what the average 'ears' will hear. With the majority of local stations levels similar, as they should be if they are at or slightly above 100% , 90.3 & 92.5 are markedly louder.

Big 121
 
Mr. Buffaloe is correct!! (I hope my spelling of your name is correct). There are many variables with modulation. You must ask does the station have a sub carrier (rds or any other), is it an IBOC station? These will affect modulation's apparent loudness. Also one old way to tell if a station is louder than another is listen to a flat car radio with the volume low. Do not try it in a GM car with it running or the auto volume level adjust will negate this. But if you want to know modulation this can only truly be measured with a properly calibrated modulation monitor can do IBOC (i.e. Audamat Aztec Golden Eagle or Day Sequara model). An analog only mod monitor is useless for comparison.
 
Apparently some modulation 'adjustments' have been made since my post. Re-measured several times yesterday
and heavy-hitters 90.3 and 92.5 are now quite close to 93.3/101.5 . I also measured the audio level on my
home recording gear; Onkyo RX (summed output) to a digital recorder with segmented VU's and manual gain
adjustment in .1db increments. As of yesterday at 3,7 and 11pm, 93.3/KGB were literally tied with the two BCA
outlets. 91X a hair lower. Total spread between them is now +/- .1 db on peaks.
On the AM side years ago, a modulation war took place in T.J. . 860, 950,1270, 1310 all raised levels to a point
that 1270 was louder than (Scott's) KSON, KCBQ, and KPOP! One day, after a few months , the levels re-
turned to 'normal'.Probably because of a visit by the authorities.. And so it goes, in Old Mexico.

Big 121
 
XEMO 860 was "fined" by the SCT after push from the FCC. That may have been several years ago. I remember even at night in North County -- before HDRadio -- the splatter on 850 and 870 was terrible.
 
Big 121 said:
Apparently some modulation 'adjustments' have been made since my post. Re-measured several times yesterday
and heavy-hitters 90.3 and 92.5 are now quite close to 93.3/101.5 . I also measured the audio level on my
home recording gear; Onkyo RX (summed output) to a digital recorder with segmented VU's and manual gain
adjustment in .1db increments. As of yesterday at 3,7 and 11pm, 93.3/KGB were literally tied with the two BCA
outlets. 91X a hair lower. Total spread between them is now +/- .1 db on peaks.
On the AM side years ago, a modulation war took place in T.J. . 860, 950,1270, 1310 all raised levels to a point
that 1270 was louder than (Scott's) KSON, KCBQ, and KPOP! One day, after a few months , the levels re-
turned to 'normal'.Probably because of a visit by the authorities.. And so it goes, in Old Mexico.

Big 121
Click to expand...

I doubt any "adjustments" have been made since your first post. I still have to question your methodology of these measurements. You really seem to have a problem with Mexican operations. I have too, but I proved it against one station with exhaustive measurements with a spectrum analyzer and FIM. You're making accusations based on an audio level meter in somewhat questionable environments. And the Mexican "authorities" don't make many visits. I doubt they'd bother for a few percent of over-mod. I happen to know the primary engineer that consults most of the border stations, some of whom you mention, and he would never sanction illegal operations.
 
Actually, in this case, the Mexican operators had no hand in this. The audio coming out of the Miramar area building is not controlled by Baja.
With me knowing a bit more than you think about this situation, give your 'buddy' a call. Ask about any 'hardware' changes made recently...
Enough said.

Big 121
 
Big 121 said:
Actually, in this case, the Mexican operators had no hand in this. The audio coming out of the Miramar area building is not controlled by Baja.
With me knowing a bit more than you think about this situation, give your 'buddy' a call. Ask about any 'hardware' changes made recently...
Enough said.

Big 121
Click to expand...

You are mysterious on so many levels.
 
RadeoEngineer said:
You are mysterious on so many levels.
Click to expand...

Nigel Tufnel: The numbers all go to eleven. Look, right across the board, eleven, eleven, eleven and...
Marty DiBergi: Oh, I see. And most amps go up to ten?
Nigel Tufnel: Exactly.
Marty DiBergi: Does that mean it's louder? Is it any louder?
Nigel Tufnel: Well, it's one louder, isn't it? It's not ten. You see, most blokes, you know, will be playing at ten. You're on ten here, all the way up, all the way up, all the way up, you're on ten on your guitar. Where can you go from there? Where?
Marty DiBergi: I don't know.
Nigel Tufnel: Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do?
Marty DiBergi: Put it up to eleven.
Nigel Tufnel: Eleven. Exactly. One louder.
Marty DiBergi: Why don't you just make ten louder and make ten be the top number and make that a little louder?
Nigel Tufnel: [pause] These go to eleven.
 
I don't scan much around here, but yesterday in the car I tuned to 102.1 and I couldn't believe how poor the sound quality was. Sounded like an old chewed up tape.
 
I never thought that the SCT had any regulations concerning modulation, although I am not at all familiar with SCT rules and regs. I recall visiting the transmitter site of 1090 in the early 1980's and saw the mod. monitor pegged behond the max. reading. George Chambers did some work for XEMO 860 in the late 70's and told me when he arrived at the transmitter site he found the station modulating at 300 percent. He turned it down to a more comfortable 150%.
 
The SCT has virtually the same regs as U.S. stations. The only one that comes to mind is that they don't allow the broadcast of religeous material.
 
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