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FM - Occasional Overmodulation

kfbkfb

kfbkfb

^^^
The FCC doesn't say a station may never deviate beyond 75kHz, only that its peak deviation must not exceed 75kHz more than 10 times a minute (pdf page 58).


Are any of the currently available FM audio processors able to overmodulate no more than 10 times/minute (skimming the product info of Orban and Omnia processors, I didn't notice anything about 10/min overmod ability)?


Kirk Bayne
 
kfbkfb said:
^^^
The FCC doesn't say a station may never deviate beyond 75kHz, only that its peak deviation must not exceed 75kHz more than 10 times a minute (pdf page 58).


Are any of the currently available FM audio processors able to overmodulate no more than 10 times/minute (skimming the product info of Orban and Omnia processors, I didn't notice anything about 10/min overmod ability)?


Kirk Bayne
Click to expand...
Your question is a technical one, not a National Radio question.
 
I don't think it's worth it. Many modern radios tolerate overmodulation only up to 110-120%, so even such occasional overmodulation won't sound good.
 
Kirk Bayne- My view is overmodulation that could be viewed as permitted will not increase loudness in a meaningful way. Processor manufacturers seek to make their customers happy, and the present toolkit is well stocked for those who want to be loud. With modern equipment, stations can be amazingly loud without being in violation of FCC rules. They don't need to get into the level of granularity you describe.

bigic- FCC permits total modulation of 110 percent under certain circumstances. Plenty of other things won't sound good, or they may sound great, depending on personal taste.

Audio is serious professional business for those who are interested in it, for whatever reason. But lots of things happen out there for various reasons, and I don't think they impact the core profession. Smile, be happy to be alive and enjoy what you do.
 
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The link is a ~35 year old article, allowing 10/min overmodulation probably wouldn't help with popular music (generally limited dynamic range).

I remembered reading the article, recent FM audio processor documents don't mention allowing occaional overmodulation.


Kirk Bayne
 
Greg Strickland said:
Kirk Bayne- My view is overmodulation that could be viewed as permitted will not increase loudness in a meaningful way.
Click to expand...
And it's important to note that FM modulation of 100% is totally arbitrary. In the US it means +/- 75 kHz, but it could be 50 kHz or 100 kHz or whatever was decided by licensing authorities to make it viable while distributing a reasonable number of stations on the band's space.

Today's receivers and transmitters are built for our current standard, and that restricts change.

AM, which varies the size (amplitude) of the carrier has a true restriction as 100% negative is total carrier supression and there is no such thing as "less than nothing" except for the resultant distortion. To some extent, AM radios are designed with the frequency bandwidth of broadcast audio in mind, and trying to do anything different runs into the limits of receivers, particularly older ones.
 
Many years ago, I worked at a local group with an AM (Top 40), FM (Classical), and TV (NBC affiliate). The Chief Engineer for the radio side was on vacation, and the assistant wasn't available, when the Commission showed up for a surprise inspection. Fortunately, I knew enough to be dangerous, so I escorted the inspector around while he made notes. We went to Master Control, which was the control point for all the stations, the FM modulation monitor for the classical station was being very active, with the peak light flashing, even to the point where the meter needle pinned on occasion for a split second. Was watching the inspector as he watched the modulation monitor, and I said something to the effect of: 'Wow, sorry about all the high peaks.' 'Are we in trouble for that?' The inspector laughed, and replied that no, absolutely not. He appreciated the fact that the station wasn't 'clipping' the audio, and that natural dynamic range of the music wasn't cause for a violation.
 
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