Will my nice FM tuner be good for a while longer or will FM turned off like analog TV? :eek:

Nope. That's the main reason for the IBOC (in-band, on-channel) strategy of the FCC. The radio stations keep their same designated frequencies, with no plan to auction off their traditional portion of the spectrum. In time, if digital receivers become ubiquitous, some broadcasters may turn off their analog modulation, but that seems unlikely during this generation.

They wouldn't dare. Analog has some advantages (robustness of signal, ability to receive analog on dirt-cheap receivers, an installed base of the better part of a billion receivers!) that guarantee it's future.

It should be noted that IBOC, as a "strategy", was NOT developed or proposed by the FCC. IBOC was designed and promoted by the broadcast industry -- the NAB and major group owners who, not so coincidentally, also own iBiquity. The FCC went along with the flow and approved the technology, although it has yet to promulgate detailed rules.

By developing a digital system that does NOT require the "sunset" of analogue broadcasting (as does HDTV), the industry guaranteed that traditional radio will be around for many years. But they dramatically reduced the incentive for consumers to embrace HD Radio.

I like HD and support it, but the naysayers (and they are many) argue that Eureka 147 would have been a far better solution to introduce digital radio in the U.S.

The only possible migration I could imagine very long term is FM stations switching to mono so they could add another HD channel. Is it possible to slip a bunch of COFDM carriers in that space without interfering with the main carrier?

Eureka 147 hasn't been a real success in the rest of the world. I'm glad we waited for better codecs, although it makes a lot more sense to dedicate a separate digital band than dealing with the potential analog interference problems. I think we'd be having fewer HD radio reception problems if they were in their own band where they could crank up the power.

Scowl,
The idea of FM stations switching to mono would be a pretty good solution.

Consider this:
- Most car radios will not decode stereo after about 30 miles from a 100kw/1,500ft station. 30 miles is also borderline for reliable HD reception, so you wouldn't gain much (if anything) for stereo in the car.

- It's probably not much different for home receivers: By the time HD Radio is un-receivable, the stereo is probably going to be pretty bad.

-You probably don't need to hear emergency broadcasts in stereo.

-In 30 years, any radio that doesn't have HD-Radio probably isn't going to be able to do stereo any way.

I kinda like to compare the adoption of HD Radio to that of Dolby-B noise reduction.

Dolby was just a nice (and somewhat) idea at first, but then became ubiquitous, and any system that didn't have Dolby on it wasn't worth buying.

Well here's an odd question...since over the air tv can be received as audio for some radios or scanners (channel 6 is 87.7 here) what will happen when that switches to hdtv or would anything happen at all ? I thought they were going to free up that bandwith for EMS or something security related.

There is a great article about the various Digital Audio broadcast services worldwide, in the newest edition of the "World Radio and TV Handbook 2007":

http://www.wrth.com/

In some places, they are planning to stop selling DAB receivers. I think it was mentioned that some countries want to end analog radio entirely. Several new schemes are taking over from the existing services. Interesting read. My WRTH 2007 was purchased last night at Borders.

Well here's an odd question...since over the air tv can be received as audio for some radios or scanners (channel 6 is 87.7 here) what will happen when that switches to hdtv or would anything happen at all ?
No TV stations will be broadcasting on channel six any more.

Scowl,
The idea of FM stations switching to mono would be a pretty good solution.
But would it work technically? I've demonstrated my ignorance of analog electronics way too many times here to figure it out myself. It seems like the station would have have to limit the bandwidth of their main carrier to 19 khz and that means no RDS or any other SCA services.

Whoops, did it again! :D

...but who cares about RDS, when the world is almost completely converted to IBOC?

No TV stations will be broadcasting on channel six any more.

Wrong. WEDY-DT (Channel 6), New Haven

I believe Channel 6 will also be used by two other stations - one in WVa, the other in Anchorage.

Well here's an odd question...since over the air tv can be received as audio for some radios or scanners (channel 6 is 87.7 here) what will happen when that switches to hdtv or would anything happen at all ? I thought they were going to free up that bandwith for EMS or something security related.

The reason it worked is because the TV sound was FM just like radio. The sound on digital tv is also digital, so no it won't work.

The eliminated channels will be 52-69

I believe Channel 6 will also be used by two other stations - one in WVa, the other in Anchorage.
You're right. Looking at the list two Alaskan stations will be on lower VHF. KYES will be switching to channel 5 after the transition and KYUK will be switching to channel 3.

A number of stations in West Virginia will be using lower VHF channels after the transition: WDTV will be channel 5, and WOAY will be channel 4.

WEDY will be using channel 6 as will KRMA in Denver, KBSD in Ensign, KS, KTVM in Butte, MT, WRGB in Schenectady, NY, WPVI in Philadelphia, and KWYP in Laramie, WY which is not broadcasting in digital yet.

The list shows about a hundred stations around the country which will be switching to lower VHF channels after analog TV is shut down. So much for freeing up that spectrum. :rolleyes:

free up that bandwith for EMS or something security related.

Since trunking allows hundreds of different users on the same 5 freqs, and the fact that trunking radios are dirt cheap now, it's really doubtful that by the time the switch is made, that communication center managers will really push to get those freqs.

The theoretical concern is while those five frequencies are more than enough to handle the traffic for a typical day, during a regional emergency trunking systems tend to overload and fail. I guess they're hoping to keep these extra frequencies in reserve.

The list shows about a hundred stations around the country which will be switching to lower VHF channels after analog TV is shut down. So much for freeing up that spectrum.

Some of these stations will change to upper VHF or UHF. KRMA, which was planning to stay on its analog channel 6, has filed with the FCC to stay on channel 18, its current digital channel. Other stations, such as WBBM in Chicago, will probably follow suit. Unfortunately, stations in rural areas, such as MT and WY, will probably not vacate lower VHF channels since they want to benefit from the coverage the lower frequencies afford them to reach more viewers. So it looks like IBOC is here to stay for some time.

Some of these stations will change to upper VHF or UHF.
Go through the channel election list at the fcc.gov web site and you'll see these hundred or so stations I'm talking about will either continue to use lower-VHF channels or in some cases move to lower-VHF channels from UHF channels.

They're a very small percentage of the stations out there (almost all stations are switching to UHF and upper-VHF) but my perception that lower-VHF would be free of televisions stations after the analog shutdown was totally wrong.

The final channel list is somewhat dated now and does not reflect subsequent filings by TV stations to change channels. But I agree that there will probably be enough stations left on lower VHF channels that the spectrum cannot be freed up for dedication to something else, such as digital radio. And if the spectrum was freed up by forcing the remaining channels to move to high VHF or UHF, Congress may mandate the spectrum be auctioned off, just like channels 52-69 will be, which could be a significant hinderance to radio stations looking at cost benefit/payback scenarios to go with digital only transmissions.

The final channel list is somewhat dated now and does not reflect subsequent filings by TV stations to change channels.
Now that I look at the FCC site closer, they also have the third round of channel elections (http://hraunfoss.fcc.gov/edocs_public/attachmatch/DA-06-1675A2.pdf) posted which includes KRMA opting for channel 18 instead of 6. It still has three stations on lower VHF including two in Georgia whose analog channels are presently UHF which must be a good deal for their coverage. This still leaves almost a hundred stations on lower VHF. I hope they have good reasons for keeping them there.

I'll bet you this is going to change by 2009, but I'm not quite sure.

I, personally want stations to stop using channels 2-6, because our VHF antennas would be a lot smaller, and more durable (elements won't break off as much).

VHF-Lo is also a lot more susceptible to ionospheric induction and other prorogation, as well as impulse noise and FM interference.

For just 5 channels, I don't think it's worth keeping the band.

I agree with everything you have said, mattdp, except that VHF-Lo may be going away. The stations that are/will be using these channels have already, or soon will be, investing in hardware, equipment, etc. to transmit on these frequencies and I don't think it's advisable or fair to change the rules at this time. Not out of the question, but I don't think you'll see it happening. These stations also like the low electric bills - they'd not be too happy pumping out 1 mW ERP on UHF versus less than 10 kW ERP on VHF-Lo

10Kw?

I know for a fact that it's 100kw for an analog station on Vhf-Lo. Are they really only going to use 10kw for the digital signal?

These stations also like the low electric bills - they'd not be too happy pumping out 1 mW ERP on UHF versus less than 10 kW ERP on VHF-Lo
TV stations are already going to use a lot more juice transmitting ATSC since it uses a consistant amount of power no matter what it's transmitting. Over the years they've found clever ways of improving NTSC transmitters by making them use the minimum amount of power necessary to transmit whatever's on the screen. New transmitters could actually pay for themselves after a few years depending on what they were replacing and how much electricity costed.

HD Radio uses a lot of juice too and for technical reasons beyond me they aren't very efficient in how they connect to the main transmitter so a lot of power is wasted.

TV stations are already going to use a lot more juice transmitting ATSC since it uses a consistant amount of power no matter what it's transmitting.

I'm not too sure what you are saying, but if you're saying ATSC transmitters will use more electricity than NTSC transmitters, I believe you are in error.

Full power VHF NTSC transmitters have ERP's of 100 kW on VHF-Lo and 316 kW on VHF-Hi. I believe that the actual amount of electricity used to produce those ERP's is far less than the actual ERP "wattage", but it is much more than what is needed (and allowed by the FCC) for ATSC transmissions to effect the same coverage of a DMA.

As examples, WBBM in Chicago on analog channel 2 has an ERP of 100 kW. It's ATSC full power transmitter on channel 3 is at 4.4 kW. For WKYC in Cleveland, those numbers are 100 kW for channel 3 NTSC, 8.0 kW for ATSC channel 2. For ATSC stations on VHF-Hi, ERP's are 18.6 kW for WFAA on channel 9, 30.0 kw for WKYT on channel 13, and 16.3 kW for WCPO on channel 10.

Similarly, NTSC UHF full power transmitters are at 5000 kW but ATSC full power transmitters are limited to 1000 kW. A rough gauge is that ATSC uses about 20% (max) of the power needed for NTSC transmissions to effect the same signal coverage.

HD Radio uses a lot of juice too and for technical reasons beyond me they aren't very efficient in how they connect to the main transmitter so a lot of power is wasted.

I'm also unsure what you mean by this statement, but the same principles that apply to NTSC television would seem to apply to NTSC (analog) FM radio. I believe FM stations, which are just above VHF-Lo TV frequencies, are limited to 100 kW also, just like NTSC TV stations. To produce an ERP of 100 kW, I believe the actual wattage (volts x amps) needed from the "electric company" is much less than 100,000 watts. And if HD radio (FM) could transmit an ATSC signal, their power requirements would significantly drop just like they do for ATSC TV to effect the same coverage.

I don't believe we'll see ATSC FM radio in the near future, not because some new bandwidth (like freeing up VHF TV channels 2-6) is needed to dedicate to the service, but because reliable mobile reception of ATSC signals (car radios) is an issue tha has not been resolved as of yet.

I'm not too sure what you are saying, but if you're saying ATSC transmitters will use more electricity than NTSC transmitters, I believe you are in error.
When our CBS affiliate got their HD transmitter going, the C.E. showed us that it used as much electricity as the NTSC transmitter they replaced over twenty years ago. Each replacement transmitter they had bought over the years had the same output but used less electricity due to various power-saving tricks NTSC transmitters have incorporated. I believe he said the NTSC transmitter they're using now uses less electricity for bright images while older transmitters would use the same amount of electricity regardless of the content. The C.E. said his station would have to go back to its 20 year old electricity budget for the ATSC transmitter.

I'm also unsure what you mean by this statement, but the same principles that apply to NTSC television would seem to apply to NTSC (analog) FM radio.
Well, no, because NTSC video is AM and uses an varying amount of power depending on what it's sending.

I don't believe we'll see ATSC FM radio in the near future, not because some new bandwidth (like freeing up VHF TV channels 2-6) is needed to dedicate to the service, but because reliable mobile reception of ATSC signals (car radios) is an issue tha has not been resolved as of yet.
Who said anything about ATSC radio? Of course it wouldn't be practical since it can't deal with multipath very well.

Ok... I guess it would work for an VHF-Lo ATSC station to operate at 10kw or less, but I would think that one would need more power to cut through all the crap in the VHF-Lo range.

Well, I think it's always been true that NTSC transmitters use less power for white than black, since negative AM is used, that is, black is maximum carrier amplitude, white is minimum. The synchronization tips actually define the maximum power and are beyond the blackest area of a picture.

The reason HD radio is so inefficient is because they have to use a power summer to insert the RF output of the IBOC transmitter into the antenna line. This requires a directional coupler whose loss determines the coupling. If you want to send 10KW of power to the antenna for the FM carrier and 100 watts (-20 dB) to the antenna for the IBOC carrier, you have to put 10KW into the directional coupler from the IBOC transmitter, 9.9KW is burned up in the termination port of the directional coupler while 100 watts makes it to the antenna.

The better IBOC implementation places the IBOC carriers into the transmitter at a low level stage in the amplifier and doesn't incur these penalties. The problem with this is that all stages past the input port must be VERY linear to faithfully pass the analog amplitude based IBOC carriers. One of the advantages of FM is that you can run the final amplifier Class C, which means you can theoretically get 100% efficiency. The Class A/B amplifiers required to faithfullm amplify the IBOC carriers probably get only 60% efficiency, the other 40% going up in heat. Harris Broadast Division makes a very cool transmitter that monitors and corrects non-linearities with a feedback loop. Trouble is that people can't necessarily afford 'forklift upgrade' transmitters, so they use the more inefficient directional coupler summing method.

Bob Smith

When our CBS affiliate got their HD transmitter going, the C.E. showed us that it used as much electricity as the NTSC transmitter they replaced over twenty years ago. Each replacement transmitter they had bought over the years had the same output but used less electricity due to various power-saving tricks NTSC transmitters have incorporated. I believe he said the NTSC transmitter they're using now uses less electricity for bright images while older transmitters would use the same amount of electricity regardless of the content. The C.E. said his station would have to go back to its 20 year old electricity budget for the ATSC transmitter.

Is this really a fair comparison? If your CBS station is KOIN, its analog signal is on channel 6 at 100 kW. Its digital signal is on channel 40 at 1000 kW. The point I was trying to make is that a digital signal requires far less ERP than an analog signal on the same range of frequencies - VHF Lo, VHF Hi, UHF. Comparing an analog VHF Lo to a digital UHF is kind of like comparing apples to oranges.

As far as my comment about ATSC FM, isn't the title of this thread about analog FM going away (digital radio)? The point I was trying to make is that it won't go away, as you correctly point out, because of multipath problems or, as I pointed out in a slightly different way, inability to receive digital signals in a mobile environment.