• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

87.7 - Chicago's "L"

T

TheIcon

MTV Tres is off 87.7, in its place is stunting? I listened from 7-8pm, heard some Johnny Cash, Dwight Yokam, Plant/Krauss, and a lot I didn't recognize.

There is imaging, identifying the station as "WLFM Chicago 87.7. First Click on the Dial. Chicago's L"

Sound quality is much better than when it was MTV Tres.
 
TheIcon said:
MTV Tres is off 87.7, in its place is stunting? I listened from 7-8pm, heard some Johnny Cash, Dwight Yokam, Plant/Krauss, and a lot I didn't recognize.

There is imaging, identifying the station as "WLFM Chicago 87.7. First Click on the Dial. Chicago's L"

Sound quality is much better than when it was MTV Tres.
Click to expand...

They're getting ready
 
Why change the format now when it's going to be changed again in 2 months? Something tells me this is an April Fools joke.
 
They simulcast late night with their sister station WLFM-LP ch6.

Is all of this coming out of little Rochelle, IL?
 
Comes in great here in Plainfield. Processing sounds like crap though.
 
They are broadcasting from the top of The Hancock Building. They are running on an STA, due to the fact they were
not able to get their final tower work done due to the lousy weather conditions. They are currently running at their
full power of 3,000 watts, they are still working on getting their antenna to it's proper height, which is taller than
what they are using now. When that work is completed they will still be at 3kw, but should have an even better signal
than they have now, due to the tower height. They have to run on the STA (Special Temporary Authority) because the
height of the tower has already been spelled out in their construction permit. If you are not able to run the station exactly
as specified in your license, you must run it on a STA to keep it legal.
 
TR1992 said:
They are broadcasting from the top of The Hancock Building. They are running on an STA, due to the fact they were
not able to get their final tower work done due to the lousy weather conditions. They are currently running at their
full power of 3,000 watts, they are still working on getting their antenna to it's proper height, which is taller than
what they are using now. When that work is completed they will still be at 3kw, but should have an even better signal
than they have now, due to the tower height. They have to run on the STA (Special Temporary Authority) because the
height of the tower has already been spelled out in their construction permit. If you are not able to run the station exactly
as specified in your license, you must run it on a STA to keep it legal.
Click to expand...

Thanks for the clarification Tri.
 
TR1992 said:
They are broadcasting from the top of The Hancock Building. They are running on an STA, due to the fact they were
not able to get their final tower work done due to the lousy weather conditions. They are currently running at their
full power of 3,000 watts, they are still working on getting their antenna to it's proper height, which is taller than
what they are using now. When that work is completed they will still be at 3kw, but should have an even better signal
than they have now, due to the tower height. They have to run on the STA (Special Temporary Authority) because the
height of the tower has already been spelled out in their construction permit. If you are not able to run the station exactly
as specified in your license, you must run it on a STA to keep it legal.
Click to expand...

I keep reading in message boards that WLFM-LP Effective Radiated Power is 3kW. (And the Pulse FM in NYC) That's the Visual Power that the FCC database is referring to. Analog TV stations never transmit at the same power for their aural transmitter as the visual signal's transmitter, in fact, it's usually no more than about 25% of the visual power in most countries. For the U.S. refer to, TITLE 47 - TELECOMMUNICATION; CHAPTER I - FEDERAL COMMUNICATIONS COMMISSION; SUBCHAPTER C - BROADCAST RADIO SERVICES; PART 73 - RADIO BROADCAST SERVICES; subpart e - TELEVISION BROADCAST STATIONS; 73.682 - TV transmission standards. http://cfr.vlex.com/vid/73-682-transmission-standards-19852080

"(15) The effective radiated power of the aural transmitter must not exceed 22% of the peak radiated power of the visual transmitter."

That means that WLFM-LP's audio that we're hearing on 87.75 MHz is actually no more than 660 watts ERP. Still it's a potent signal from 383 meters (1256 feet) Above Ground Level. And Pulse FM (WNYZ-LP) in NYC [the other LP TV being used as a radio station] is only 213 meters (699 feet) AGL so we have a better signal in the Chicago area and WLFM-LP's antenna is higher than almost all of the buildings in Chicago, unlike WNYZ-LP's antenna, which is being shadowed by many buildings taller than 700 feet in NYC.
 
stormy01 said:
I keep reading in message boards that WLFM-LP Effective Radiated Power is 3kW. (And the Pulse FM in NYC) That's the Visual Power that the FCC database is referring to. Analog TV stations never transmit at the same power for their aural transmitter as the visual signal's transmitter, in fact, it's usually no more than about 25% of the visual power in most countries. For the U.S. refer to, TITLE 47 - TELECOMMUNICATION; CHAPTER I - FEDERAL COMMUNICATIONS COMMISSION; SUBCHAPTER C - BROADCAST RADIO SERVICES; PART 73 - RADIO BROADCAST SERVICES; subpart e - TELEVISION BROADCAST STATIONS; 73.682 - TV transmission standards. http://cfr.vlex.com/vid/73-682-transmission-standards-19852080

"(15) The effective radiated power of the aural transmitter must not exceed 22% of the peak radiated power of the visual transmitter."

That means that WLFM-LP's audio that we're hearing on 87.75 MHz is actually no more than 660 watts ERP. Still it's a potent signal from 383 meters (1256 feet) Above Ground Level. And Pulse FM (WNYZ-LP) in NYC [the other LP TV being used as a radio station] is only 213 meters (699 feet) AGL so we have a better signal in the Chicago area and WLFM-LP's antenna is higher than almost all of the buildings in Chicago, unlike WNYZ-LP's antenna, which is being shadowed by many buildings taller than 700 feet in NYC.
Click to expand...

Yep, 660w/383m is still a pretty potent signal.

Keeping in mind that I'm an engineer, not a lawyer... I'm not convinced that 22% limit applies to LPTV. Indeed, under the old rules, before digital LPTVs were allowed, I believe there was no limit on the aural power of a LPTV. (it could even exceed the visual power)

Part 73 of the FCC regulations applies only to full-power and Class A TV stations. WLFM and WNYZ are neither; they hold low-power licenses. Low-power licenses are regulated under Part 74. So the 73.682 you cite does not directly apply to these stations.

74.735 (http://edocket.access.gpo.gov/cfr_2008/octqtr/47cfr74.735.htm) limits the maximum peak effective radiated power (ERP) of an analog low power TV station to 3kw VHF, 150kw UHF. It doesn't specify whether that means aural or visual. I would certainly *presume* they meant visual, but I think it can be interpreted as both.

I can find no other rule in Part 74 that applies to the aural power of an analog LPTV. 74.780 contains a list of regulations under Part 73 which also apply to Part 74 LPTV stations, but 73.682 (which limits the aural power of a full-power analog station) is not among them. 74.750 "Transmission system facilities" also references two regulations in Part 73, but neither has to do with limits to aural power.

(73.687(b)(3) would appear to limit the *modulation* of an analog LPTV to +/-25KHz, which would be 33% modulation as received on an FM radio. However, it also qualifies that with the phrase "for monophonic transmission" and indicates "...unless some other peak modulation level is specified in an instrument of authorization..." -- presumably the FCC could give WLFM special dispensation to operate at FM modulation levels?

I might guess this was an unintentional oversight when the LPTV service was created. The service grew out of the TV translator service -- TV translators were required to relay a full-power station, and were not allowed to materially alter the characteristics of the full-power signal. So if the full-power station was in compliance with the 22% limit, and the translator was in compliance with the requirement to not alter the signal, then the translator would by default be limited to 22% aural power.

Now, I would not count on *my* interpretation of the rules to order your equipment or answer the FCC Inspector!
 
Well, if that's the case, that's fine. 3kW (or more) would be welcomed by those who want a more reliable signal. Does anyone have an idea if RBDS (RDS) would work on WLFM-LP? it seems that the Stereo signal for WLFM-LP is about normal in volume compared to the "real" FM stations, though I can agree that they are compressing the audio to make up for the tighter deviation.
 
stormy01 said:
Well, if that's the case, that's fine. 3kW (or more) would be welcomed by those who want a more reliable signal. Does anyone have an idea if RBDS (RDS) would work on WLFM-LP? it seems that the Stereo signal for WLFM-LP is about normal in volume compared to the "real" FM stations, though I can agree that they are compressing the audio to make up for the tighter deviation.
Click to expand...

I see no reason you couldn't run R(B)DS on the aural carrier of a TV station.

I don't see where processing alone could come anywhere near close to bringing WLFM's audio up to a level comparable to that of a "real" radio station. If they aren't MUCH quieter than the FM stations, then they have to be running significantly more than 25KHz peak deviation. From correspondence with DXers I'm sure WNYZ *is* running significantly more than 25KHz and wouldn't be at all surprised if WLFM is doing likewise. I would expect either station's audio to be rather distorted if tuned on a TV set.

The caveat about all these "TV-6-as-radio-station" operations is that they *are* still TV stations (albeit low-power) and *will* eventually be required to switch to digital operation. The FCC has not yet set a drop-dead date for analog operation of LPTV stations (it's definitely NOT the June 12th date that applies to full-power stations) but the Commission has clearly stated that they *will* set a drop-dead date.

After that date, WLFM, WNYZ, the planned L.A. station, and all the others will cease to be viable as radio stations. They'll have to either do TV or go dark.
 
Came across an interesting snippet about WNYZ-LP in NYC testing as WNYZ-LD(?) with the 87.75 carrier still running in Analog (!)

"DIGITAL CHANNEL 6 IN NYC

News from the New York City metro area: I caught WNYZ-LD Channel 6 on the air this evening using virtual channel 1-1 for an over-the air display. Pulse 87, the quasi-FM station using analog aural carrier frequency 87.75 MHz, was still on the air.

It looks like they are going to try to make the digital TV signal and the faux 'FM' signal co-exist. Very interesting to see. Reasonable reception seen about 45 miles north of NYC in Northern Westchester."

http://www.w4uvh.net/dxlatest.txt (DX LISTENING DIGEST 9-033, April 14, 2009)
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom