Audio Processor and FM Signal Range

[everydayguy]

I'm not an engineer, but a programing guy, but was wondering this:

An expensive powerful audio processor like the omnia 6 can make stations sound real loud, but does that mean people who live near the edge of the signal will pick up the station more clearly?

Another words, is there a relationship between a big loud processor and being able to hear an FM station a little further out even though the station power is the same?

Thanks in advance for your answer.

 

[bossbill]

In my humble opinion, no. It's a different story with AM radio, especially if one takes advantage of running higher positive peaks, up to the 125% limit. With AM, the instantaneous power output increases, and it will help cut through the noise, although audio quality can suffer, especially with agressive clipping.

With FM, we're changing the frequency very rapidly to accomplish the modulation. While you'll get an increase in loudness which may be apparent, you still need quieting for it to sound good.

 

[Chuck]

It probably won't help real fringe areas very much, but processing, properly done, can mask some problems in weak signal areas. It makes snaps, crackles and pops a bit harder to hear to the casual listener. They are still there, but most people won't notice them. Good processing is also helpful to get over the noise floor found in most cars. That in itself can be a plus.

On the other hand, extremely aggressive processing can be very tiresome to listen to. The tendency seems to be "if a little is good, then a lot is better." That isn't necessarily the case. Your TSL may suffer. "Everything in moderation" would be a better credo.

 

[NE Miss Radio]

Don't think it wouold be too interesting for a music station, but mono typically goes farther than stereo.

 

[whit979]

The thing I have noticed with Omnia processors is that they don't extend the reach of the signal, but they keep it sounding good farther out. With some other brands there is a tendency for the highs to go away completely once you get into that fringe area. That seems to be less of a problem with Omnias. Just my opinion but this seems to be a rather consistent result where I live.

 

[everydayguy]

Gentlemen -- thanks a lot for your info so far -- it is much appreciated.

Makes me wonder how much further we might get out with our 6kw FM signal if we broadcast in mono and use a big market processor -- its an oldies format.

 

[Goat Rodeo Cowboy]

Gentlemen -- thanks a lot for your info so far -- it is much appreciated.

Makes me wonder how much further we might get out with our 6kw FM signal if we broadcast in mono and use a big market processor -- its an oldies format.

I guess one could take the attitude that Oldies do not need stereo to still be appealing to the audience/consumer of Oldies.

Part of what you wrote in this post ventures beyond engineering and technical. We don't know anything about your power or your market place. Let's assume for the sake of discussion you have a good reach for 40 miles out. Let's assume you go mono and now you reach, what.... 44 miles? 46 miles? Who is out there and how many are out there. What have you lost if you don't reach them? What have you lost if you focus your energy and staff energy on reaching out an extra four miles and you take your eye off the ball and forget what the people are wanting 10, 15 and 18 miles from your station.

 

[whit979]

Gentlemen -- thanks a lot for your info so far -- it is much appreciated.

Makes me wonder how much further we might get out with our 6kw FM signal if we broadcast in mono and use a big market processor -- its an oldies format.

Having worked at a 6kW FM myself, I can tell you that it won't make much of a difference -- but stereo enhancement will hurt you for sure. Maybe keep it in stereo, but just don't use any extra spatial enhancement?

 

[TomT]

I have a Class A (=6 kw) in the upper Ohio Valley. Classic rock format. Antenna sits on a 1200 ft. hill, the population is all in the valley--a narrow ditch at this point, at 600 feet. We get out about 20 miles before the signal falls apart--because of the terrain.

A couple of observations. First, understand that most "FM" radios do not have true FM detectors, but instead use what are essentially a variant on AM detectors. So over-modulation (over-deviation, to be precise) does work--to a degree. You will sound louder as you crank it up--until the point where you overload the IF strip and everything goes to pieces quite rapidly. Unfortunately, you don't know where that point is on all of the radios out there. But that will explain why some stations sound louder even though your modulation monitor is pinned at 100%--they may be running at 130%!

This will give you more apparent range--simply because all that audio covers up the noise in a weak signal, but may not sound that great in close. Used to also mean a citation from the FCC, but they don't seem to worry about such things any more.

Second, better processing certainly can help--if it is set up right. Jumping from an Orban 8100 to a modern digital processor will make a noticeable difference. I have Omnia 3T's, I just installed an Omnia One, and I know a local station has an Omnia 6. I can hear the difference, but you get what you pay for. Most of the major manufacturers will be helpful on giving you suggested setting or presets. However, processing can't compensate for signal problems introduced by transmitter/antenna deficiencies. In my area a big problem is multipath. Our signal bounces back and forth in the valley like a ping-pong ball--so the direct signal receives interference from the reflected signal, i.e.--multiple path interference. Especially on the side of the valley under the tower.

Turning off the stereo can help with multipath, but a better transmitter will give you a cleaner stereo signal. We switched from a tube type transmitter (Harris 2.5H) to a Nautel V2, (solid state) and noticed an immediate improvement in areas prone to multipath.

Another area that can be neglected is the antenna. Typical class A installations run between one and three bay antennas, depending on the actual power needed and how much someone wanted to spend on an antenna. Have all three combinations locally, can't say there is much difference in coverage. I have noticed difference in coverage between brands of antennas.

 

[rrsounds]

I'm not an engineer, but a programing guy, but was wondering this:

An expensive powerful audio processor like the omnia 6 can make stations sound real loud, but does that mean people who live near the edge of the signal will pick up the station more clearly?

Another words, is there a relationship between a big loud processor and being able to hear an FM station a little further out even though the station power is the same?

Thanks in advance for your answer.

My experience? Yes! But...

In the good old analog days when the most sophisticated processor was the 8100, my first really serious CE job included a little class A FM (3kW) whose main competitor was a full class B (50kW). Our 8100 was at the studio, with a 950MHz composite STL to the transmitter site.

The PD drove me around the coverage area. On his car radio, there were some pretty important town parts where our signal was adequate, but occasionally a little noisy. Where our signal was good we were the same loudness as the class B. The area was flat (beach community) so there wasn't much in the way of multi-path. It was just weak signal. Was there anything (cheap!) we could do?

Having heard some stories about composite clipping that were mostly positive, I asked the GM if we might try out a Modulation Sciences CP-803 at the transmitter.

By backing off the high-frequency processing of the Optimod and judiciously increasing input to the CP-803, we gained in overall level, and those little problem areas simply disappeared. I was impressed, because we had lost no perceptible quality, yet were louder. The PD and GM were equally impressed, because the little $900 gamble (cost of CP-803) had paid off.

My conclusion was/is that, in the huge span of processing possibilities that ranges from no processing -> pure distortion, every step you can take to increase your loudness level and its consistency allows you to overcome background noise, even with 'noise-free' FM. Some of these steps are simply overcoming inefficiencies, such as in this case, where overshoots caused by the STL were hurting our modulation level.

Some of it is simply keeping the level consistent, so the moments of low level (perceived as noisy) audio are rare.

But as they say, use a light hand. At the point of diminishing returns, you will begin to reduce quality in ways that are much worse than a few clicks and pops!

Today's digital processors are much more sophisticated and can hide their distortion really well, for the most part. But they are still a knife through the heart if pushed too far.

Kind Regards,
David

PS: Yes, we kicked the class B's butt. At least until they discovered composite processing! LOL!

 

[everydayguy]

Thanks to all on this Board for your excellent responses!

To David Reaves: sounds like it might be worth it for us to demo the Modulation Sciences CP-803.

Also -- we may try to broadcast in mono for a day or so to see if that gives us a slight boost, but my hunch is we'd best keep the stereo humming along since we're music intensive.

 

[cgould]

Thanks to all on this Board for your excellent responses!

To David Reaves: sounds like it might be worth it for us to demo the Modulation Sciences CP-803.

Also -- we may try to broadcast in mono for a day or so to see if that gives us a slight boost, but my hunch is we'd best keep the stereo humming along since we're music intensive.

Well,

If your existing processor has a built-in composite clipper, then there will be nothing much to gain by adding a CP-803 to the output. You'd be doubling up on the composite clipping -- and that would make things worse.

If you have an old 8100 processor, and it is *not* equipped with the "Card Zero" addition, then you can play the comp. clipper game if you wish...

Be careful with the 803. Too much composite clipping can cause an apparent decrease in coverage as the "harmonic garbage" from the old style composite clipping can pile up in the subcarrier regions and possibly create modulation related multipath in some difficult reception areas. If you run subcarriers, this hash from heavy CP-803 composite clipping will cause "crashing" sounds in the subcarrier audio whenever there is significant high frequency energy on the main program audio signal.

Modern DSP processors employ new composite clipper designs that greatly reduce - if not eliminate- this problem....

-Cornelius

 

[rrsounds]

Thanks to all on this Board for your excellent responses!

To David Reaves: sounds like it might be worth it for us to demo the Modulation Sciences CP-803.

Also -- we may try to broadcast in mono for a day or so to see if that gives us a slight boost, but my hunch is we'd best keep the stereo humming along since we're music intensive.

Welll.... ;D The episode I described was over 25 years ago!

I used it to illustrate that processing can cover noise in FM, not necessarily as a "how-to"!

With power goes responsibility....LOL!

Please read Cornelius' previous note carefully. Anything I would say would just be repetition.


Kind Regards,
David