Broadcast Signal Transmission Quality

[raymeedc]

Can somebody shed some light on a subject that has been perplexing to me for quite a while? I don't understand why radio stations don't put out a higher quality signal. I know it can be done, as my local Classical music station puts out a beautiful, high quality, strong signal, practically indistinguishable from the signal I get from my CD player. Every other station in my area (New York City) sounds like garbage. Fortunately for me, I listen primarily to classical & Jazz (which I'm forced to listen to in mono from a local college station, understandable, considering the budget they work with). The classical station is a public radio, non-profit station that relies on donations. If they can afford a high quality transmitter, why can't the commercial stations do the same. I would like, once in a while, to listen to some rock or folk/blues for a change, but they are so unpleasant to listen to, I don't bother anymore. I can't understand why this is.

[OvenMaster]

What the broadcasters do is compress the dynamic range of the signal to make it sound "louder" at the expense of sound quality.

I remember reading years ago that the number one person the broadcasters are looking for is someone in their car, looking for a station to listen to. When they start pushing pre-sets or scanning the FM band, usually the listener will stop on loud stations because the "loudness" grabs their attention.

Presto: another set of ears to listen to their advertising. Mission accomplished.

Tom

[electronjohn]

You got that right, OvenMaster. The amount of compression (and CLIPPING) applied to FM audio is just plain criminal. It's not the engineers, either...they'd much rather run clean, minimally-processed audio. It's the tin-eared program directors who demand the "loud" sound...and the more competitive the market the worse it is. Just as bad back in the days of AM music stations...compression was so high in some cases that drumbeats would "punch holes" in the signal. And don't even talk to me about the short life of modulator tubes in those poor abused AM transmitters. I actually blew the plate cap out of an 833 running heavy compression and 125% asymmetrical modulation!

[Punker X]

Source is also a consideration, Listening to a classical or jazz/blues station you are more likely to listen to a CD or Vinyl Record, where listen to the a Top 40 or Classic Rock station you are more than likely listening to a computer file.

Deviation - % of modulation is another consideration. Some Kenwood tuners had a Deviation meter. Should run around 75% with occasional peaks to 100%, Some stations you see it running 100% with peaks over 120%. Make is sound louder, but also distorts the signal.

[KentTeffeteller]

Gentlemen,

I refuse to run heavily compressed and over deviated audio. Sounds awful! I run lightly on the compression. Against my values as a broadcast engineer. I also have the advantage with this radio group of being family owned. :tresbon:

[electronjohn]

Keep fighting the good fight!!

[Holst]

Gentlemen,

I refuse to run heavily compressed and over deviated audio. Sounds awful! I run lightly on the compression. Against my values as a broadcast engineer. I also have the advantage with this radio group of being family owned. :tresbon:

Bless you good sir.

I can also point out that the various herds of radio stations under various forms of the same ownership (that's the best way I could think of saying it) that electronjohn and I work for are pretty good at promoting quality over loudness. We also benifit from sharing a consulting engineer with public radio.

[gyusher]

I have a question. . .

How good can it be?? What I mean is just how good or just how capable is the format itself plus what's typical of a decent signal?? I know humans can hear 20-20K or so to speak. What are the limitations of the FM Stereo format??

I spent 25 years with my KT-917 and the last few getting used to lesser tuners with a few highly modded or upgraded tuners thrown in for good measure. I have listened to both good and bad with all thats between. I know when its good it can be very good. . .

[OvenMaster]

Guy, the FCC broadcast standard for FM transmitters in the main L+R channel is 50Hz to 15kHz, but I cannot remember the maximum frequency response deviation in decibels. I'm pretty sure that it's 1dB or less.
http://edocket.access.gpo.gov/cfr_2006/octqtr/pdf/47cfr73.310.pdf
Tom

[gyusher]

Guy, the FCC broadcast standard for FM transmitters in the main L+R channel is 50Hz to 15kHz, but I cannot remember the maximum frequency response deviation in decibels. I'm pretty sure that it's 1dB or less.
http://edocket.access.gpo.gov/cfr_2006/octqtr/pdf/47cfr73.310.pdf
Tom


Ed Zackery (as RuSsman would say) what I wanted. . .

[KentTeffeteller]

Hi,

Maximum deviation in db from frequency response is 1 db. This standard dates from 1948 and the beginning of the modern FM band.

[mhardy6647]

and always remember that the compatible FM MPX stereo pilot signal is at 19 kHz, setting an absolute, brick wall upper limit on frequency response.