Overmodulating

[BossJock1947]

Don't know why several big companies can't play by the rules and modulate legally instead of jacking it up past 130%

Wish the FCC would investigate and fine these jerk-offs more often. Why have rules and regulations if a few are allowed to ignore them.

Are you listening Dan?

 

[BobOnTheJob]

Same thing with the local cops...when was the last time you saw someone come to a complete stop at a stop sign? Either laws should have teeth or they should be removed from the books.

 

[fm-engineer]

Don't know why several big companies can't play by the rules and modulate legally instead of jacking it up past 130%

Wish the FCC would investigate and fine these jerk-offs more often. Why have rules and regulations if a few are allowed to ignore them.

Are you listening Dan?

130 is a good FM average in some places. In most cases, there is really no enforcement of modulation levels. On AM the positive limit is 125. Most major markets run in excess of 150 or 175.

 

[bossbill]

Is there any documentation or anecdotal evidence that a higher FM modulation level increases listenership in any way? Would a radio listener gravitate to the louder station?

With AM, modulation level and density does make a difference in overcoming noise in fringe areas, and the fact that the modulation is changing the amplitude of the RF signal. But with FM, the modulation does not effect quieting, does it?

Back when there was no limit on positive modulation, most transmitters couldn't take advantage of it due to tube and power supply limitations. Now that many transmitters are using some form of pulse-width modulation, all one has to do is adjust the resting duty cycle, and achieve positive levels far exceeding the FCC limit.

 

[wgliradio]

This is one of the follies of the new digital processors.

Station X and Y are around 130%

If I were to make Station X have the same perceived loudness as station Y, yet modulate legally, station X would not sound very pleasant, even with the most modern whiz/bang audio processor.

While older analog boxes like the 8100 have their own set of distortions, the newer boxes tend to mask these "classic" distortions, but they also sound hideous doing so when "modern distortions" cause the audio loses detail and it grunges up.

I can tell you that if you run, lets say, an Ariane/8100 or even an 8100/XT2 vs a modern digital box (i have more than a few at my disposal), if you disregard the speed limit, both will sound outstanding (in most cases, I am very biased towards the technology that made the 8100 the wonder that it is).

If you run one vs the other where one box is obeying the speed limit, with the 8100 you start getting that classic midrange buzz on guitar/female vocals. With the digital box, that midrange distortion is masked very well, but at the expense of audio that loses alot of detail.

It's basically pick your poison, but analog or digital, trying to compete with clipping and staying legal will never ever sound better than the guy across the street who ignores the speed limit. No matter what the idea... Low IM clipping, look ahead limiting.. etc etc, it's still brute control on the audio and the side effects pop out somewhere.

 

[KR4BD]

Years ago, the FCC did strictly enforce technical issues with stations.

Here's a little story in which I was personally involved.

In 1969, I was on the air at WVUD-FM (Now WLQT) in Dayton, OH. One afternoon, two FCC inspectors from the Detroit Field Office showed up at the studio door and wanted access. They flashed ID, etc., so I let them in. I still have the business card from one of them....His name was Bernard L. Stuecker. The first thing they wanted to do was check all the operator licenses on the studio wall (a time when such things were required). Then, they went over to the remote transmitter meters and started a set of readings, which were required every 30 minutes at that time. Then, they had me do an EBS test for them.... I was so busy trying to answer their questions and help them with the readings that an album I was playing tracked into the next cut. When this happened, the intercom from the office came on and wondered if I was OK. I told them I had "visitors" and could someone come down to help out.

A few minutes later, the PD showed up and almost panicked when he saw who my visitors were! Then, FCC guys said they wanted to go to the transmitter about a mile away, so our PD summoned our CE who showed up in 10 or 15 minutes to take them away to the transmitter. When they got there, I still remained busy comparing readings in the studio with the readings on the transmitter.

Anyway, an hour or so later, they left, at which time our CE instructed us all to call all the other stations in town (WONE, WING, WAVI, WHIO, etc.) telling them we had been "visited". I called WHIO and they said they had had a similar visit three days earlier. WING said the same thing. No ONE called us! Anyway, after the inspection, we got an "official" letter slapping our wrists for hitting 102% on modulation peaks, but no fines. Other stations in town were not so lucky. WKEF-TV, as I recall, was heavily fined for severe overmodulation as a result of the inspections.

These FCC guys had been in town for a week in their "unmarked truck" monitoring everyone. Beside the technical stuff, they also requested to see specific broadcast logs from certain dates to match information that had obtained on their own. We were fortunate in that all the public files, Meter Reading logs, Program Logs, etc., were readily available.

Does the FCC still do these inspections?

 

[oldiesstation]

Seems like they just respond to complaints.Years ago i advised an FM to get legal.Fell on deaf ears(no pun intended).appears there was a FCC monitoring station close by.After paying that fine,they decided to play it my way.I hear stations everywhere that are exceeding legal mod limits,not just large market ones.

 

[radiorob2.0]

In the case of FM isn't it really about modulation carrier deviation as long as you're within +/-75khz?

I had read somewhere, one of those radio urban legends, that Randy Michaels while still at CC ordered his AM's to run positive modulation beyond 125 percent. His school of thought was the risk of the fine was worth the loudness.

 

[kyscott]

Inspectors are still out there. They ask to see the public file, EAS logs and the tower. That's it. We had a field inspector in Louisville not too long ago. She never asked anyone to run an EAS test. She didn't ask if anyone knew how to turn off any of the transmitters and she didn't want to SEE the transmitters, just the tower. The Enforcement bureau isn't what it used to be.

 

[gtomas]

The thing is, like Mike said, you can easily make a station with an entry-level processor to be perceived to sound louder AND better than the station with a top-of-the-range processor, if the latter one obeys the modulation limit and the first one does not.

Similarly, if two stations are using the same processor and one of these station decides to overmodulate, even just a little bit, it can sound much better than a legal station. Simply because it does not have to drive its processor as hard to match or surpass the loudness of the other station. It can use less clipping, less density and have more bass and cleaner high end.

To gain a 0.5 dB of extra loudness over the same processor if both are set to exactly the same peak modulation level is very hard. However, to achieve the same by overmodulating is very easy. And cost free (unless the regulatory body is strict in enforcing the modulation limit).

This is why those inspectors (not just in US) need to keep a closer eye on deviations and this is why, when comparing the processors and/or stations, you have to be sure that they have precisely the same peak modulation level. Otherwise you are not making an objective comparison.


Regards,
Goran Tomas

 

[Sgeirk]

Nearly all stations I see do not have a modulation monitor in the studio, what stations I do see? Their monitors haven't been calibrated in eons... In very few shops do I see a station that has their own fully functional simple spectrum analyzer.

Plus, when there's an average of one engineer for every 4 stations in the country* , and an FCC inspector for every 300*, is it any wonder modulation isn't set right?

*PURELY MADE UP FACTS AND FIGURES

 

[rorban]

In addition to violating the law, overdeviating is a bad idea because it makes some (but not all) FM radios produce lots of IM distortion because of narrow IF bandwidth. IIRC, Ford gave a presentation to the NRSC about this. The insidious thing is that not all radios are troublesome, so overmodulators can easily fool themselves.

 

[OKCRadioGuy]

My experience is that anything over about 120 percent isn't a good idea (FM). I have a friend's station (he's the manager) that the owner originally had set the audio up to somewhere around 150 percent or so. It sounded OK locally but further out from the station the chopping was pretty evident. Now that the station is at least turned down to within the guard-rails it sounds MUCH better. He had to turn it down very slowly to keep the owner from noticing because "he liked his station louder than others", etc. Now if we could only get rid of that parametric EQ that's in front of his 8100XT/2. We may try bypassing it but keeping all the pretty lights still going just to keep from getting someone's attention.

 

[TomT]

Remember, too, that most radios do not use true FM detectors, but some kind of slope detection. Within limits, more modulation = louder station.

Then add to this formula the following:

GM/SM's who got into radio during the top 40 AM days (they will be in their 50's now), who equate good audio with loud, squashed audio. E.G. Optimod 9000 into a plate modulated transmitter.

Car salesman (and other businessmen) who don't listen to radio except when you are trying to sell them on the merits of your station--they check you out on the nearest radio to see if you are as loud as the other stations in town.

Hence: 130% mod.

On the FCC inspectors: Unless there is an interference complaint from public safety, FAA, or a foreign government, all they care about is that your registered tower has a very visible number (where they don't have to get out of their car to see it) the paint looks good, and the lights are lit at night. At the studio, they want to see the public file--"issues" lists up to date, public and broadcasting (the latest version) in the file, EAS tests received and sent, tower lights checked.

Doubt that some of them would know what a transmitter is if they were standing in front of one.

 

[BobOnTheJob]

Remember, too, that most radios do not use true FM detectors, but some kind of slope detection. Within limits, more modulation = louder station.

Then add to this formula the following:

GM/SM's who got into radio during the top 40 AM days (they will be in their 50's now), who equate good audio with loud, squashed audio. E.G. Optimod 9000 into a plate modulated transmitter.

Car salesman (and other businessmen) who don't listen to radio except when you are trying to sell them on the merits of your station--they check you out on the nearest radio to see if you are as loud as the other stations in town.

Hence: 130% mod.

On the FCC inspectors: Unless there is an interference complaint from public safety, FAA, or a foreign government, all they care about is that your registered tower has a very visible number (where they don't have to get out of their car to see it) the paint looks good, and the lights are lit at night. At the studio, they want to see the public file--"issues" lists up to date, public and broadcasting (the latest version) in the file, EAS tests received and sent, tower lights checked.

Doubt that some of them would know what a transmitter is if they were standing in front of one.

My favorite to date is when an FCC Inspector observed the normal reading on an antenna current meter being in the lower 1/3 of the scale (a violation). In his words "Man this thing is hard to read". End of story. With Inspectors like him, modulation isn't even on the radar screen.

 

[greg.hahn]

In the case of FM isn't it really about modulation carrier deviation as long as you're within +/-75khz?

That is correct, and with FM, the number is arbitrarily assigned. In other words, 75 KHz deviation is 100% modulation in the FM broadcast band because somebody at the FCC decided that's what it would be. They could have just as easily picked 50 KHz or 100 KHz. Other FM services, like RPU (marti equipment) and two way, use 5 KHz deviation for 100%. With less deviation, the channels are more narrow. The noise level is higher. But they can pack more users into the spectrum.

So for FM broadcast, it's 75 KHz, that's above and below your center frequency. So the FM channel is 150 KHz wide, with a 25 KHz "guard band" on either side, for a total of 200 KHz, or 0.2 MHz. And that is why we have FM channels every 0.2 MHz. 103.1, 103.3, 103.5, etc.

103.1 occupies the space from 103.0 to 103.2. And 103.3 occupies the space from 103.2 to 103.4 and so on.

If 75KHz is 100% modulation, then 10% modulation is 7.5 KHz. So
110% modulation is 82.5 KHz deviation.
120% is 90 KHz deviation.
130% is 97.5KHz deviation.

 

[Studio1]

So the FM channel is 150 KHz wide, with a 25 KHz "guard band" on either side, for a total of 200 KHz, or 0.2 MHz. And that is why we have FM channels every 0.2 MHz. 103.1, 103.3, 103.5, etc.

US frequency steps have always intrigued me. Here in New Zealand (as with other countries) we use 100 kHz steps - our tuners run 88.1, 88.2, 88.3, 88.4 etc.
That doesn't mean of course that we allocate licences that are 100 kHz apart. In fact, at the moment, commercial licences are 400 kHz apart - 97.0, 97.4 etc (in the same local area).

One problem we do have is low power (I think you call it "part 15"). There is no official allocation of frequencies - it is up to the operator to select an "unused" frequency that won't interfere with others. Naturally, the frequencies are just a sea of noise and distortion, as there are too many stations all swamping the same or adjacent frequencies.

As far as over modulation goes, I don't believe that the authorities here are that concerned about it. I have a QEI 691 monitor and I regularly observe many commercial stations operating in excess of 150%.
What really worries me though are the low power operators. I know of none who have any kind of test gear to observe or set their mod levels. When I have quizzed them on how they know what levels they are transmitting at, I either get a blank look and a shrug of the shoulders, or the reply that "we turn it up until it starts to distort then we back it off until it sounds Ok" !!

 

[DJRobbioRobbio]

So the FM channel is 150 KHz wide, with a 25 KHz "guard band" on either side, for a total of 200 KHz, or 0.2 MHz. And that is why we have FM channels every 0.2 MHz. 103.1, 103.3, 103.5, etc.

When I have quizzed them on how they know what levels they are transmitting at, I either get a blank look and a shrug of the shoulders, or the reply that "we turn it up until it starts to distort then we back it off until it sounds Ok" !!

You would be shocked and amazed at how many PD/ SD and some engineers think that same way....

My biggest problem that I have with over-modulation is that fact that it just CREAMS the little guys on the fringe, especially if they're LPFM, or a station at a lower wattage that's following the rules.... I just wish the FCC would start doing its job of enforcing the modulation rules, as opposed to just keeping them in the books as a "well if we catch you" kind of thing...

 

[cgould]

In addition to violating the law, overdeviating is a bad idea because it makes some (but not all) FM radios produce lots of IM distortion because of narrow IF bandwidth. IIRC, Ford gave a presentation to the NRSC about this. The insidious thing is that not all radios are troublesome, so overmodulators can easily fool themselves.

Yes!!!

I have a couple of radios like that, where 100% modulation means the radios are already producing some IM distortion. Those radios come in handy as a tool to make sure dense processing at 100% is not so dense that these radios "fall over the cliff" too far.

-Cornelius

 

[jesseg]

In the case of FM isn't it really about modulation carrier deviation as long as you're within +/-75khz?

I had read somewhere, one of those radio urban legends, that Randy Michaels while still at CC ordered his AM's to run positive modulation beyond 125 percent. His school of thought was the risk of the fine was worth the loudness.

I'm a friend of his, and wouldn't believe it unless he told me. And I wouldn't go repeating it publicly.

But, I wouldn't put it past anyone. It's like... in 65 MPH speed limit, and the traffic is doing 75 MPH along side police doing the same thing. Do you go 65 MPH and put yourself in danger of getting read ended? Or go 75 MPH and keep up?

Personally... I would report the speeders to the FCC. But as a huge network, where doing that would be a logistics nightmare and make a lot of enemies and potentially never accomplish the goals in many markets... I would probably just drive 75 MPH.
;D

I just wish the FCC would start doing its job of enforcing the modulation rules, as opposed to just keeping them in the books as a "well if we catch you" kind of thing...

amen.