2nd FCC DAB report/order

[dbdigital]

I'm sure many of you have already read the FCC's 2nd report and order regarding IBOC. What I thought was interesting was item 4, paragraph 57 on LPFM.

It stated:"... that IBOC-based equipment can operate at the 100 watt power levels authorized for LPFM service. iBiquity asserts that in the case of 10 watt stations, however, the extremely low power level of those stations may make digital broadcasts infeasible. The IBOCsystem broadcasts the digital signal at one percent of the station’s analog power level. In the case of a 10 watt LPFM station,
that digital power level would fall below the noise floor and would be difficult for any digital receiver to recover; however, this would not be the case with 100 watt LPFM stations."

I could be wrong but I don't think this bodes well for the creation of the LPFM-10 service or for the FCC approving any service at power levels less than 100 watts.

db

 

[dbdigital]

Apparently John Anderson over at DIY Media agrees with my assessment as to why the FCC has been slow to initiate the LPFM-10 service.

"Interestingly, iBiquity says that the as-yet unapproved 10-watt LPFM station class will not be able to adopt its HD technology, given the "extremely low power level" of these stations. If such stations will effectively become obsolete in an all-digital future, this may explain why the FCC has refused to sanction their proliferation."

http://www.diymedia.net/

db

 

[clouseau]

Apparently John Anderson over at DIY Media agrees with my assessment as to why the FCC has been slow to initiate the LPFM-10 service.

"Interestingly, iBiquity says that the as-yet unapproved 10-watt LPFM station class will not be able to adopt its HD technology, given the "extremely low power level" of these stations. If such stations will effectively become obsolete in an all-digital future, this may explain why the FCC has refused to sanction their proliferation."

http://www.diymedia.net/

db

This is an interesting assertion. And NOT a good one. (Not that I think the potential LP10's will be in line to buy HD.)

Does this have something to do with a "Linear Scale" not really being the case with the "Digital to analog" ratio?

I do a modest amout of FM plotting (And applying), but don't really have a good software program that will do below the "1 Watt" level.

What are the actual numbers on this? "Digital signal level at analog 100 watt 60 Dbu contour" vs "Digital signal level at analog 10 watt 60 Dbu contour".

Anyone have the software to answer this question?? Should the FCC allow higher Digital levels on these ultra small stations? (Which might screw up the ratio and actually damage analog).

Who has numbers???

Clouseau

 

[rfry]

What are the actual numbers on this? "Digital signal level at analog 100 watt 60 Dbu contour" vs "Digital signal level at analog 10 watt 60 Dbu contour". Anyone have the software to answer this question?? Should the FCC allow higher Digital levels on these ultra small stations? (Which might screw up the ratio and actually damage analog). Who has numbers???

For a transmit antenna 100 feet above average terrain, the FCC's F(50,50) FM propagation curves show the 60 dBµV/m (1 mV/m) contour at 3.53 miles for 100 watts ERP, and 1.97 miles for 10 watts ERP.

Note that these are the average field strengths 9 meters above the earth, at those distances. The fields are reduced in approximately a linear relationship to the reduction of the receiving antenna height from 9 meters (ie, 1/2 the height = 1/2 the field).

FM HD radios allegedly are supposed to play well in digital out to the 1 mV/m analog contour of the station (no matter what ERP produced that signal strength). But an HD FM receiver with an antenna near the earth such as an auto receiver, or on a low floor of a building and using no outside antenna, or in dense urban environments probably will have to be closer to the transmit antenna than shown in these numbers in order to work well.

//

 

[dbdigital]

Apparently John Anderson over at DIY Media agrees with my assessment as to why the FCC has been slow to initiate the LPFM-10 service.

"Interestingly, iBiquity says that the as-yet unapproved 10-watt LPFM station class will not be able to adopt its HD technology, given the "extremely low power level" of these stations. If such stations will effectively become obsolete in an all-digital future, this may explain why the FCC has refused to sanction their proliferation."

http://www.diymedia.net/

db

This is an interesting assertion. And NOT a good one. (Not that I think the potential LP10's will be in line to buy HD.)

Does this have something to do with a "Linear Scale" not really being the case with the "Digital to analog" ratio?

I do a modest amout of FM plotting (And applying), but don't really have a good software program that will do below the "1 Watt" level.

What are the actual numbers on this? "Digital signal level at analog 100 watt 60 Dbu contour" vs "Digital signal level at analog 10 watt 60 Dbu contour".

Anyone have the software to answer this question?? Should the FCC allow higher Digital levels on these ultra small stations? (Which might screw up the ratio and actually damage analog).

Who has numbers???

Clouseau

Oh, that's right! You're the guy with the translator (who's trying to get the FCC to change its status to a full service station). Well, if your translator is licensed for 10 watts, and many of them are, then you're out of luck as far as getting any coverage with it in HD-R.

That's tough.

db

 

[rfry]

iBiquity asserts that in the case of 10 watt stations, however, the extremely low power level of those stations may make digital broadcasts infeasible. The IBOC system broadcasts the digital signal at one percent of the station’s analog power level. In the case of a 10 watt LPFM station, that digital power level would fall below the noise floor and would be difficult for any digital receiver to recover; however, this would not be the case with 100 watt LPFM stations."

The point I hoped to make in my earlier post in this thread was that it doesn't matter to an HD-FM receiver the exact value of the ERP that generated the 60 dBµV/m (1 mV/m) or greater analog field in which its receiving antenna is immersed. HD-FM as now authorized should work fairly well when the receiving antenna sees a 1 mV/m or better field strength, regardless of the transmission system that generated that field strength -- even if it had an analog ERP of only 10 watts.

It may be a poor ROI for the possible number of HD receivers well-served by a 10 watt analog FM with HD, but if the station owners don't care, why should anybody else?

//

 

[dbdigital]

iBiquity asserts that in the case of 10 watt stations, however, the extremely low power level of those stations may make digital broadcasts infeasible. The IBOC system broadcasts the digital signal at one percent of the station’s analog power level. In the case of a 10 watt LPFM station, that digital power level would fall below the noise floor and would be difficult for any digital receiver to recover; however, this would not be the case with 100 watt LPFM stations."

The point I hoped to make in my earlier post in this thread was that it doesn't matter to an HD-FM receiver the exact value of the ERP that generated the 60 dBµV/m (1 mV/m) or greater analog field in which its receiving antenna is immersed. HD-FM as now authorized should work fairly well when the receiving antenna sees a 1 mV/m or better field strength, regardless of the transmission system that generated that field strength -- even if it had an analog ERP of only 10 watts.

It may be a poor ROI for the possible number of HD receivers well-served by a 10 watt analog FM with HD, but if the station owners don't care, why should anybody else?

//

I'm just going by what I read. If iBiquity, who created the technological mess they call HD-Radio, says it won't work successfully with 10 watts then who am I to disagree. Apparently, the FCC isn't questioning it either.

db

 

[audio4tv]

Apparently John Anderson over at DIY Media agrees with my assessment as to why the FCC has been slow to initiate the LPFM-10 service.

"Interestingly, iBiquity says that the as-yet unapproved 10-watt LPFM station class will not be able to adopt its HD technology, given the "extremely low power level" of these stations. If such stations will effectively become obsolete in an all-digital future, this may explain why the FCC has refused to sanction their proliferation."

http://www.diymedia.net/

db

This is an interesting assertion. And NOT a good one. (Not that I think the potential LP10's will be in line to buy HD.)

Does this have something to do with a "Linear Scale" not really being the case with the "Digital to analog" ratio?

I do a modest amout of FM plotting (And applying), but don't really have a good software program that will do below the "1 Watt" level.

What are the actual numbers on this? "Digital signal level at analog 100 watt 60 Dbu contour" vs "Digital signal level at analog 10 watt 60 Dbu contour".

Anyone have the software to answer this question?? Should the FCC allow higher Digital levels on these ultra small stations? (Which might screw up the ratio and actually damage analog).

Who has numbers???

Clouseau

The issue is the current authorization of the IBOC power levels. 100 watts would be 1 watt Digital power. 10 watts would be .1 watt, which is appraoching the noise floor, and thus why Ibiquity is stating it would not be feasible for those power levels. FYI, 1 Watt would not be that bad, as there is a station in San Francisco that is operating at 6watts HD and covers their area pretty well, with the height they have.

 

[rfry]

100 watts would be 1 watt Digital power. 10 watts would be .1 watt, which is appraoching the noise floor, and thus why Ibiquity is stating it would not be feasible for those power levels.

Sorry, but for all other things equal except ERP and coverage area, the digital field strength at the 1 mV/m analog FM field strength contour of a hybrid FM+HD signal meeting the iBiquity/FCC specification is just as capable of serving a digital receiver at that contour if the station's analog ERP is 10 watts as if it is 100 kW (or any other value).

Receivers of digitally-modulated r-f signals do not need the raw signal strength of analog systems for acceptable performance.

This is a reality of physics that cannot be denied -- whether by iBiquity, the FCC or any other source.

R. Fry http://rfry.org
//

 

[Timewarp]

IBOC will fail because the internet will prevail. Digital cassette recorders seemed like a
good idea too. But, someone else came up with CD burners.