How can a LPTV station on CH 6 legally broadcast audio using FM Stereo standards with a 19KHz pilot and 75kHz modulation instead of MTS TV standard of 15.7kHz pilot and 25kHz modulation? Question Legal status and would not using FM Stereo causes interference to the video? Will FCC crack down on station like Pluse 87.7 (LPTV- 6) in New York?
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ch6 LPTV and FM stereo
- Thread starter mgpt6
- Start date
I've often wondered if Pulse 87.7 adheres to the mono 25khz limitation. Do they?
It will be interesting to see how well this does. FCC shows it has 3KW and the audio portion is generally 10% of the video or 300 watts in this case. And it's directional to boot. But it appears to be smack dab in the middle of the population center. 300 watts in NYC is probably worth more than 100,000 watts in Dufus Flats, Idaho. How far does this one reach (in air miles) on a car radio?Nick said:
BobOnTheJob said:
You of course catch me on the road & away from my copy of the rules but.....
As I understand it, it is perfectly legal for a TV station (full- or low-power) to use the FM stereo standard. A station that uses a stereo pilot at 15.75KHz must use the TV standard -- but the FM pilot is at 19KHz. Using the FM stereo standard does NOT cause interference to other stations, nor to the station's own video signal. There is a chance the station's own video signal could interfere with its sound, though that's probably a lot less likely with newer non-CRT TVs. (that have a LOT less horizontal sweep energy floating around) That source of interference should never have affected reception of the station's sound on an FM radio.
The way I read it, it is NOT legal for a TV station (full- or low-power) to use the FM radio deviation standard. That would be defined as 300% modulation which is no more legal for TV than it is for FM. However, it seems VERY unlikely the FCC isn't aware of Pulse operating at 300%, and at this point they haven't done anything about it.....
The regulation for full-power TV stations limits the aural power to no more than 22% of visual. It's common practice to operate at 10%. I have to think I was reading the low-power regulations wrong, but the way I read them, before the rules were changed to accomodate digital LPTV, *there was no limit* to the aural power of an analog LPTV. [0]
When the rules were changed to allow digital LPTV, the way I read it the same 3kw limit that applies to the visual was applied to the aural. So if I'm reading it right, WNYZ could be running as much as 3kw ERP aural.
When the FCC reports the power of a directional FM or TV station, they're reporting the power in the direction of maximum signal. So if Pulse is listed as running 3kw directional, that means 3kw is the highest power they run at any azimuth. At some azimuths, it's less than 3kw.
[0] before this channel-6-LPTV-as-radio-station thing came along, there was no reason to run the aural at a power more than about 20% of visual - because no TV receiver could even decode the audio signal in the absence of a usable video signal, and because the aural programming was useless in the absence of useful video.
There are hundreds of 100,000 watt stations in many Dufus Flats, Idaho's around the country that serve major metro areas. But that's another thread.
I don't think the FCC even looks at LPTV. One here is lucky to do 5 KHz modulation. Another's about 400% modulation. They've been that way for years.
I don't think the FCC even looks at LPTV. One here is lucky to do 5 KHz modulation. Another's about 400% modulation. They've been that way for years.
BobOnTheJob said:
I believe the 10% aural 'rule' is more a convention then a rigid rule. I know of LPTVs that run over 50% aural power and are perfectly legal. That measn that this station could run up to about 2 kW aural power and still be okay.
Also, there is no rule with LPTVs requiring the same visual and aural information and aklso they can run separate transmitters for visual and aural. I know of one channel 6 LPTV that does just that-they have two separate transmitters and antennas for each. The aural is a regular 2 kW FM transmitter run at about 900 watts out. It goes into a 7db gain vertically polarized log periodic antenna. This is located on a hill where the B1 FMs are derated to 1200 watts ERP. You do the math on this one....it runs power similar to that of a class B FM station.
LA_Guy said:
Some of this is replying to my own post:
73.682(a)(15): "The effective radiated power of the aural transmitter must not
exceed 22% of the peak radiated power of the visual transmitter."
http://edocket.access.gpo.gov/cfr_2008/octqtr/47cfr73.682.htm
73.682(c)(3) (partial): "Other methods of multiplex subcarrier or stereophonic aural transmission systems must
limit energy at 15,734 Hz, 20 Hz, to no more than 0.125 kHz aural carrier deviation.
("other methods" means stereo systems other than the BTSC analog TV stereo standard - for example, the FM standard. 0.125kHz aural carrier deviation probably wouldn't yield a useful signal.)
74.735(a):
" (a) The maximum peak effective radiated power (ERP) of an analog low
power TV, TV translator, or TV booster station shall not exceed:
(1) 3 kW for VHF channels 2-13; and
(2) 150 kW for UHF channels 14-69."
http://edocket.access.gpo.gov/cfr_2008/octqtr/47cfr74.735.htm
(doesn't say whether visual or aural -- they definitely mean visual - I would read that to indicate aural is also limited to these figures.)
74.780 lists those full-power rules that apply to LPTVs. Note that 73.682 is not among them!
http://edocket.access.gpo.gov/cfr_2008/octqtr/47cfr74.780.htm
The way I read this, 74.735(a) is the only regulation limiting the aural power of a LPTV station.
Slightly OT but... For years, 74.735(a) read:
"The power output of the final radio frequency amplifier of a VHF low power TV, TV translator, or TV booster station, except as provided for in paragraphs (d) and (f) of this section, shall not exceed 0.01kW visual power. A UHF station shall be limited to a maximum of 1 kW peak visual power except as provided for in paragraph (f) of this section. In no event shall the transmiting apparatus be operated with a power output in excess of the manufacturer's rating."
There was no limit to the effective radiated power of a LPTV station. (except for the need to avoid interference, and the limit to how much antenna gain could be obtained. You can't get 316kW ERP from a 10-watt transmitter without an impractically large (and directional) antenna.) Two LPTVs in upstate New York were briefly authorized with in excess of 400kW ERP through the use of highly directional antennas.
(paragraph (d) allowed LPTVs operating on unused full-power channel allotments to operate at 100 watts transmitter output. Paragraph (f) stated that if circular polarization is used, the transmitter output limits are doubled -- 0.01/1kW horizontal and 0.01/1kW vertical.)
Ok, enough speculation. Look here for the story on how this all got started:
http://kyes.info/engineering/linklist/kznddocs/kznd.html
KZND-LP was an LPTV in Anchorage, AK. My friend Jeremy was reading the FCC rules one day long ago and found that part 74 rules are not the same as part 73 rules. The rules, oddly enough, allow things when they don't specifically say that things are not allowed. Separate programming for aural and visual carriers, maximum power of 3KW on VHF, with nothing specific said about visual or aural power. 75 khz deviation, stereo pilot, whatever. And in the documents you will find at the link above, the FCC decided that as long as there was both visual and aural programming, the LPTV could do what it wanted to. End of story.
Just because nobody had figured this out before and that some broadcasters became upset at a new competitor means very little. Read the rules yourselves, and then get back to the FCC about how you don't like the way they are written. Oh, and good luck with that.
When the LPTV digital rules are established and analog LPTV goes away, it will change. But for now, welcome to the way it is. By the way, I built the LPTV 6 station here on Kaua`i in 2003. It's 3KW on Ch. 6, has separate visual and aural programming, and made one of the local FM stations pretty mad at first. Nothing I can do about that, however.
http://kyes.info/engineering/linklist/kznddocs/kznd.html
KZND-LP was an LPTV in Anchorage, AK. My friend Jeremy was reading the FCC rules one day long ago and found that part 74 rules are not the same as part 73 rules. The rules, oddly enough, allow things when they don't specifically say that things are not allowed. Separate programming for aural and visual carriers, maximum power of 3KW on VHF, with nothing specific said about visual or aural power. 75 khz deviation, stereo pilot, whatever. And in the documents you will find at the link above, the FCC decided that as long as there was both visual and aural programming, the LPTV could do what it wanted to. End of story.
Just because nobody had figured this out before and that some broadcasters became upset at a new competitor means very little. Read the rules yourselves, and then get back to the FCC about how you don't like the way they are written. Oh, and good luck with that.
When the LPTV digital rules are established and analog LPTV goes away, it will change. But for now, welcome to the way it is. By the way, I built the LPTV 6 station here on Kaua`i in 2003. It's 3KW on Ch. 6, has separate visual and aural programming, and made one of the local FM stations pretty mad at first. Nothing I can do about that, however.
Don Mussell said:
Well, there's an interesting point. I *swear* I saw something that obligated LPTVs to adhere to full-power modulation levels -- but that's not among the regulations cited in 74.780, and I can't find anything else that establishes a limit on LPTV aural modulation.
(I wonder if there was a reference to aural modulation limits in the LPTV rules in the past? Maybe I screwed up & used my 13-year-old printed copy of the rules?)
There are a LOT of people inside even the smallest circle. Anyone know what power the audio portion of Pulse is actually using? And what runs on the video portion? Non Stop TV spots for Pulse?Nick said:
This is the coverage map
http://img268.imageshack.us/img268/5924/pulse.jpg
http://img268.imageshack.us/img268/5924/pulse.jpg
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