WRGB may be able keep analog 87.7 carrier intact after digital transition.

[pqgeorge]

From the WRGB/Schenectady site:

>>What will happen to WRGB's audio on 87.7 FM?
We hope that the FCC will allow us to continue to operate on 87.7. We are building a unique transmitter for 87.7 that can operate simultaneously with our DTV signal on channel 6. TV transmissions always use horizontal antennas. Our new 87.7 transmitter will be vertically polarized. The use of vertical polarization for 87.7 will allow reception of our audio in a car radio or any other FM radio with a whip type antenna. <<

This might fly. Any station planning to use channel 6 after 2/17/09, like WRGB, could take advantage of this little unique opportunity. Since Channel 6 is right below the present FM band, any FM radio could pick it up. Since they no longer have an analog video component, they could switch to standard 75u FM pre-emphasis to keep the audio as high as the normal FM stations in the market. It would be a decent public service due to the news and public affairs programming that WRGB is known for. It was America's first TV station since 1928. I say, hey... why not? I hope the FCC will let them do it.

 

[tripinva]

That would be a first; I've never heard of anything like this.

- Trip

 

[fybush]

That makes two of us - and I wonder how it would fly against the absolute Congressional prohibition against continued analog full-power broadcasting after 2/17/09.

If nothing else, it may explain why WRGB wants to stay on 6...

 

[w9wi]

From the WRGB/Schenectady site:

>>What will happen to WRGB's audio on 87.7 FM?
We hope that the FCC will allow us to continue to operate on 87.7. We are building a unique transmitter for 87.7 that can operate simultaneously with our DTV signal on channel 6. TV transmissions always use horizontal antennas. Our new 87.7 transmitter will be vertically polarized. The use of vertical polarization for 87.7 will allow reception of our audio in a car radio or any other FM radio with a whip type antenna. <<

This might fly. Any station planning to use channel 6 after 2/17/09, like WRGB, could take advantage of this little unique opportunity. Since Channel 6 is right below the present FM band, any FM radio could pick it up. Since they no longer have an analog video component, they could switch to standard 75u FM pre-emphasis to keep the audio as high as the normal FM stations in the market. It would be a decent public service due to the news and public affairs programming that WRGB is known for. It was America's first TV station since 1928. I say, hey... why not? I hope the FCC will let them do it.

I find it VERY VERY VERY difficult to believe this can be made to work without causing massive interference to WRGB's own digital signal. Multipath is going to at least partially undo the cross-polarization attenuation, and at that point at many DTV receivers, there's going to be a big fat (very fat!) analog FM carrier in the middle of the channel. Which is going to make WRGB disappear on many (most) DTV receivers.

WRGB would also have to roll off their DTV signal above 87.5MHz or so, dropping the top 500KHz. Otherwise, the DTV signal would clobber analog FM reception. I highly doubt a compatible DTV signal could be broadcast without using that 500KHz. (the data rate is fixed at 19.2Mbps)

While there's nothing in the rules to prevent an analog TV-6 station from using the FM stereo standard and 75uS pre-emphasis, there *is* something to prevent the use of the 75KHz FM peak deviation figure. "100% modulation" for TV sound is defined at 25KHz - 75KHz to match FM radio would amount to 300% modulation.

Though I suppose if the FCC were willing to waive enough other rules to allow this to happen, I suppose it would be reasonable to expect them to waive the rule prohibiting 300% aural modulation!

And then there's the legal issue Scott brings up.

I wouldn't bet the stray dimes under my bed that this will ever happen.

 

[Reaperducer]

That would be a first; I've never heard of anything like this.

- Trip

Not really a first. I've seen several stations in Texas and the midwest on 6 that promote their evening news at 87.7 on billboards so that people driving home can listen to the local news.

Right now in NYC there's an LPTV on 6 that exists solely to feed FM radios. I don't even know if it bothers to broadcast a video carrier since the content is all radio and that's how it brands itself.

 

[w9wi]

That would be a first; I've never heard of anything like this.

- Trip

Not really a first. I've seen several stations in Texas and the midwest on 6 that promote their evening news at 87.7 on billboards so that people driving home can listen to the local news.

Right now in NYC there's an LPTV on 6 that exists solely to feed FM radios. I don't even know if it bothers to broadcast a video carrier since the content is all radio and that's how it brands itself.

What Trip is referring to as a "first" is the idea of a station being able to run a *DTV* signal and an analog FM audio signal on the same channel at the same time. Nobody else has proposed such a thing. Probably for the good reason that it cannot be done.

 

[Reaperducer]

Anything can be done, and other stations around the country are considering it. However... the people at WPVI in Philadelphia make a good point about why they're not going to do it.

Since the audio was being picked up as part of their analog signal before, they didn't have to pay any extra for the content.
BUT if they run a separate radio service on 87.7, then there are all sorts of licensing and payment arrangements that have to be taken into consideration.

Greed is what will kill this for all the old channel sixes in the nation. Not the technical side.

 

[kenglish]

If this works, then they've found the solution to the "ABC ISSUE", as the FCC calls it.
Just have all the FM stations, in each market where DTV broadcasts in VHF, switch to vertical-only polarization. That would stop FM from interfering with channel 6 DTV, and would prevent the overload of digital TV tuners by FM (which causes 2nd order distortion). :

 

[W2JUV_AL]

BTW the audio from WRGB is now on 87.9 Mhz. Rumored to be 3-4KW ERP. I was in northern Oneida County NY (Forestport) a few days ago and could receive it quite well on a Jeep factory radio.