Channel Sharing Question

[Peter Parker]

In Channel Sharing Arrangements will the respective channels actually share a transmitter or might they each transmit from their own transmitter. here in Norther Virginia two different stations have shared channel 30 since the digital transition and they each use their own transmitter. I was curious if this would become more common or whether the host station will simply allocate bandwidth to the tenant using their legacy transmitter.

 

[navychop]

I didn't think it was possible to use two transmitters. I guess they have a firm line drawn across the frequencies used.

 

[Peter Parker]

Again. Just curious. I know that in the case of the MHz stations they actually use different frequencies but both map to channel 30. I am unaware of any current case where they use the same channel from different locations.

 

[HoTat2]

In Channel Sharing Arrangements will the respective channels actually share a transmitter or might they each transmit from their own transmitter. here in Norther Virginia two different stations have shared channel 30 since the digital transition and they each use their own transmitter. I was curious if this would become more common or whether the host station will simply allocate bandwidth to the tenant using their legacy transmitter.

Nah ... don't think so ....

CSAs mean that one station surrendered their RF channel in the auction for financial compensation and will share another station's RF channel using different sub-channels mapped to the virtual channel numbers of either sharer.

 

[harshness]

I don't think they necessarily have to pick one or the other's virtual channel number. I think I have at least one RF channel that broadcasts different virtual subchannels as fill-in.

On the other side of the coin, my local PBS station (KOPB) appears to be broadcasting from at least two different towers at different frequencies and having all the subchannels show up in sequence. Earlier Trip pointed out that they were sending two HD streams, two SD streams and a bunch of audio on a single carrier, but now it appears that they may be using two transmitters that are less than 4 miles apart for their Portland feeds. There is a third transmitter that can't be much more than 20 miles away from the other two and I'm not sure what that's about.

 

[HoTat2]

That's what I was trying to say ....

With CSAs you can have different sub-channels on the same RF carrier, but mapped to different virtual channel numbers.

And I expect to see this for a number of stations in the LA market here over the next serveral years for the ones which gave up their spectrum at auction to enter into CSAs.

 

[Jim5506]

A station can broadcast from two different locations using the same virtual channel as long as the real channel frequencies are different - what a waste of watts.

 

[ancient]

A station can broadcast from two different locations using the same virtual channel as long as the real channel frequencies are different - what a waste of watts.

It's not a waste if the two transmitters give coverage to parts of the viewing area that otherwise would not receive an acceptable signal. In some places, particularly those at some distance from any major city, viewing areas can be quite large geographically and it would be nearly impossible for a single transmitter to provide an acceptable signal. I would imagine that mountains would also impede signals and possibly necessitate multiple transmitters if full coverage is desired. Remember that reception and reliable reception are two different things - people stop watching channels that lose the signal while they are trying to watch their shows.

What I don't get is reusing the same channel numbers. It makes it real difficult to tell which transmitter you're tuning in when they are have the exact same channel numbering. Unless maybe they are just picking up the raw signal from the main tower and retransmitting it without any processing whatsoever.

 

[comfortably_numb]

Here in the Kansas City region, WROB, KMJC and KCKS all broadcast from different tower locations but use the same virtual channel number 25. This enables them to cover most of the metro by using 3 different LP signals. One in Topeka, one in Basehor, and one in Louisburg. All 3 have different UHF "real" channel numbers. It works pretty well. One of the 3 (KCKS) is getting booted in the upcoming repack, so I'm not sure yet where it will go.