Missing FM pilot

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nfr
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Missing FM pilot

Post by nfr » Mon Oct 31, 2016 7:12 pm

A nearby class A college radio station is transmitting FM stereo without a 19 kHz pilot. The 38 kHz stereo information is still being transmitted but no pilot. This has been this way for over a year. My question, is this within the FCC rules to have such a modulation.
On the FCC website I read that you would need to run a proof if adding FM stereo but nothing about removing stereo . Or does it not much matter as long as the deviation bandwidth is within 75 kHz. I want to encourage the station to fix or replace the stereo generator and not to continue mono with a useless stereo subcarrier.
Last edited by nfr on Tue Nov 22, 2016 10:57 am, edited 2 times in total.

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BroadcastDoc
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Re: Missing FM pilot

Post by BroadcastDoc » Mon Oct 31, 2016 8:08 pm

I don't believe that is covered in the rules anymore. As long as the occupied bandwidth doesn't exceed 75kHz, I wouldn't expect much concern by the FCC.

Any particular reason why it's bothering you?
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w9wi
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Re: Missing FM pilot

Post by w9wi » Tue Nov 01, 2016 6:12 am

What Doc said.

By my reading of 73.319 and 73.322 what you're seeing is perfectly legal.

Pointless, but legal.
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nfr
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Re: Missing FM pilot

Post by nfr » Tue Nov 01, 2016 11:31 am

BroadcastDoc wrote:I don't believe that is covered in the rules anymore. As long as the occupied bandwidth doesn't exceed 75kHz, I wouldn't expect much concern by the FCC.

Any particular reason why it's bothering you?
It really does not bother me much other than it is not really correct. Kinda like a really messy cable install at a transmitter site, it could be fixed. But as the other hams in our club have categorized me and a couple other hams as a Super 33+ guy. As in regular electrical tape on coax connections is not good enough when Scotch Super 33+ is what is supposed to be used. I just like to see things correct.

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Re: Missing FM pilot

Post by Deep Thought » Tue Nov 01, 2016 1:07 pm

You only need a "proof" (occupied bandwidth measurements) when you change something that can affect said occupied bandwidth. That includes a new transmitter, exciter or stereo generator.
§73.1590 Equipment performance measurements.

(a) The licensee of each AM, FM, TV and Class A TV station, except licensees of Class D non-commercial educational FM stations authorized to operate with 10 watts or less output power, must make equipment performance measurements for each main transmitter as follows:

(1) Upon initial installation of a new or replacement main transmitter.

(2) Upon modification of an existing transmitter made under the provisions of §73.1690, Modification of transmission systems, and specified therein.

(3) Installation of AM stereophonic transmission equipment pursuant to §73.128.

(4) Installation of FM subcarrier or stereophonic transmission equipment pursuant to §73.295, §73.297, §73.593 or §73.597.

(5) Installation of TV stereophonic or subcarrier transmission equipment pursuant to §§73.669 and 73.1690.

(6) Annually, for AM stations, with not more than 14 months between measurements.

(7) When required by other provisions of the rules or the station license.

(b) Measurements for spurious and harmonic emissions must be made to show compliance with the transmission system requirements of §73.44 for AM stations; §73.317 for FM stations and §73.687 for TV stations. Measurements must be made under all conditions of modulation expected to be encountered by the station whether transmitting monophonic or stereophonic programs and providing subsidiary communications services.
The only thing the FCC cares about stereo-wise is that if you are not running the 'approved' FM multiplex stereo system you must make sure you do not have any significant modulation (<125 Hz deviation) at 19 KHz +/-20 Hz and that anything at or above 23 KHz does not cause more than 53% of the total modulation, and if you are running it you meet those specs.

Just turning off the pilot does not trigger any measurements.
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Re: Missing FM pilot

Post by BroadcastDoc » Tue Nov 01, 2016 1:40 pm

nfr wrote:
BroadcastDoc wrote:I don't believe that is covered in the rules anymore. As long as the occupied bandwidth doesn't exceed 75kHz, I wouldn't expect much concern by the FCC.

Any particular reason why it's bothering you?
It really does not bother me much other than it is not really correct. Kinda like a really messy cable install at a transmitter site, it could be fixed. But as the other hams in our club have categorized me and a couple other hams as a Super 33+ guy. As in regular electrical tape on coax connections is not good enough when Scotch Super 33+ is what is supposed to be used. I just like to see things correct.
Oh, I totally understand that. Drives me nuts when things aren't "right" either. Who knows, perhaps they have a reason for it (or not - something might be broken).
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nfr
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Re: Missing FM pilot

Post by nfr » Tue Nov 01, 2016 2:19 pm

Thanks for all the replies. It looks like other than not able to listen in stereo there is no real way to encourage them to fix it. I was hoping to be able to make a case for them to fix it. The bad part is the college has the money to fix it. But the professor really does not care much about the radio part of the broadcast course. They mostly emphasize the television which is run over a internal cable system. Again thanks for the reply.

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KPJL FM
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Re: Missing FM pilot

Post by KPJL FM » Wed Nov 02, 2016 8:07 am

But, but, they can get 8 -9% more loudness, and double their coverage area!
Yeah, it's sarcasm. Unfortunately, some managers/owners don't understand that.
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Re: Missing FM pilot

Post by Dale H. Cook » Wed Nov 02, 2016 8:36 am

nfr wrote:...the other hams in our club have categorized me and a couple other hams as a Super 33+ guy.
I am a Super 88 plus mastic plus Super 88 plus Scotchkote guy. :-)
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nfr
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Re: Missing FM pilot

Post by nfr » Wed Nov 02, 2016 8:41 am

Since the station is not doing anything wrong I might as well let everyone know the call letters for the station are KTCC.

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Re: Missing FM pilot

Post by ChuckG » Wed Nov 02, 2016 7:03 pm

Offer to fix it at no cost.
A buck fiddy says it's an analog generator with a dirty injection pot or edge connector. I've had 8100's do this.
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Re: Missing FM pilot

Post by Deep Thought » Wed Nov 02, 2016 9:57 pm

ChuckG wrote:Offer to fix it at no cost.
A buck fiddy says it's an analog generator with a dirty injection pot or edge connector. I've had 8100's do this.
Or someone who bumped the pilot switch. :lol:
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Re: Missing FM pilot

Post by COMMENG » Fri Nov 11, 2016 9:45 am

nfr wrote:Since the station is not doing anything wrong I might as well let everyone know the call letters for the station are KTCC.
Well, you did that in the first post.

Now that you know it is not illegal, go to the station's website and address an email to the engineer in care of the Station Manager, and inform them of the situation, listing the equipment you used to determine the "no pilot' condition.

Seems simple enough.

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ncradioeng
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Re: Missing FM pilot

Post by ncradioeng » Mon Nov 14, 2016 3:24 pm

The stereo decoder requires the 19 kHz tone to be able to properly regenerate the 38 kHz subcarrier in the correct phase relationship to recover the L and R channels. So sayeth Zenith.

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Re: Missing FM pilot

Post by W2XJ » Mon Nov 14, 2016 4:38 pm

How did you determine that they are still running the MPX subcarrier?

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