Digital signal strength when analog goes out

[cah1975]

Will a channel's digital signal strength increase once that particular station's analog signal is cut off? I live in Southwest Michigan and can receive all the South Bend, IN locals but the Chicago channels I get are very inconsistent in their strength.

 

[Tower Guy]

Will a channel's digital signal strength increase once that particular station's analog signal is cut off? I live in Southwest Michigan and can receive all the South Bend, IN locals but the Chicago channels I get are very inconsistent in their strength.

Type your address into TV Fool - Home. Click on the box "Post-Transition". See what you will get. Right now WWMT and WBBM interfere with each other. Both of them will be changing channels.

 

[Peter Parker]

Intersting. I have ocasonal problems with one digital cahnnel in my area and according t the TV fool database it will reduce its signal post transition.

 

[ciwsguy]

Geronimo,
A reduction in output power after the transition doesn't necessarily mean you will not being able to pickup the signal. If you look at the dBm listings for the channels in your area, you may see that the dBm numbers and output power of the channels for your address aren't linear. So output power alone isn't the only driver, but it is a combination of (a) the distance from the transmitter, (b) the sensitivity of your receiver, and (c) the output power. Doubling output power doesn't give the station that much more reach to the receivers.

What signal strength does your receiver show for the station in question?

 

[Peter Parker]

Geronimo,
A reduction in output power after the transition doesn't necessarily mean you will not being able to pickup the signal. If you look at the dBm listings for the channels in your area, you may see that the dBm numbers and output power of the channels for your address aren't linear. So output power alone isn't the only driver, but it is a combination of (a) the distance from the transmitter, (b) the sensitivity of your receiver, and (c) the output power. Doubling output power doesn't give the station that much more reach to the receivers.

What signal strength does your receiver show for the station in question?

At no point did I sayI would not receive the signal or even question whether I would. I simply said that it is interesting that the database shows thatfor one station the output power will be reduced.

 

[Tower Guy]

At no point did I sayI would not receive the signal or even question whether I would. I simply said that it is interesting that the database shows that for one station the output power will be reduced.

Reducing power is not the same as reducing its signal. A VHF signal requires less power for the same coverage.

Go by the dbm values in tvfool. If the dbm value goes down, your original statement is correct. If the dbm goes up (less negative), its likely that the lower power actually offers better coverage.

 

[Peter Parker]

Both the pre and post transition signals are UHF. And yes the value is less negative. Which would seem logical under the circumstances. I am surprised if this is accurate data---I am not saying that it is not just that I am surprised that the station would do this.

the differences are minor and I have no reason to believe that it wil affect my ability to watch the channel post transittion . But I still find it curious. That is all I have said.

 

[Jim5506]

Err... doesn't less negative mean a stronger signal??

 

[ciwsguy]

Err... doesn't less negative mean a stronger signal??

Yep!

 

[Peter Parker]

excuse me guys I meant more. I know that you are dtermined to conclude that the signal is equal to or better than the pre transition one. But all I said was that I I think it odd that they would tweak it down

 

[Tower Guy]

excuse me guys I meant more. I know that you are dtermined to conclude that the signal is equal to or better than the pre transition one. But all I said was that I I think it odd that they would tweak it down

Lower UHF channels work better than higher channels.

Any station 52 and above must move to a lower channel in February, 2009.

 

[Peter Parker]

True but no one said anything about VHF or channels over 52. Why are people fillling in details like taht?

 

[NightHawk]

Reducing power is not the same as reducing its signal.

What?

 

[mdonnelly]

What?

I imagine he means that reducing transmitter power along with moving to a lower frequency could result in increased signal coverage.

 

[NightHawk]

I imagine he means that reducing transmitter power along with moving to a lower frequency could result in increased signal coverage.

OK, but lowering transmitter power never provides better coverage.

Lowering frequency only provides better coverage if we jump down far enough to switch to a much larger receive antenna, say from UHF to the VHF band. It's only the receivers larger antenna that provides better signal strength, not the lower frequency itself.

Some of these web calculators can be misleading

 

[Tower Guy]

What?

Here's what I mean. Let's say that you live at 41.9464, -86.3389; Berrien Springs, MI

Right now WLS is transmitting on channel 52 at 19.86 KW ERP. According to tvfool the signal strength is -128.6 dbm.

In February, 2009 WLS will move to channel 7 and run 3.2 KW ERP. The calculated signal strength is -113.9 db.

In this case the power will go down 7.93 db but the signal strength will go up 14.7 db.

 

[Tower Guy]

OK, but lowering transmitter power never provides better coverage.

Lowering frequency only provides better coverage if we jump down far enough to switch to a much larger receive antenna, say from UHF to the VHF band. It's only the receivers larger antenna that provides better signal strength, not the lower frequency itself.

Some of these web calculators can be misleading.

Tvfool is not misleading, but it can be misinterpreted.

The path loss varies with frequency. That calculation is intertwined with the size or "capture area" of a dipole at a certain channel. That "dipole factor" enters the path loss calculation twice, once in the receive end, and a second time at the transmit end.

 

[NightHawk]

Here's what I mean. Let's say that you live at 41.9464, -86.3389; Berrien Springs, MI

Right now WLS is transmitting on channel 52 at 19.86 KW ERP. According to tvfool the signal strength is -128.6 dbm.

In February, 2009 WLS will move to channel 7 and run 3.2 KW ERP. The calculated signal strength is -113.9 db.

In this case the power will go down 7.93 db but the signal strength will go up 14.7 db.

Your example holds true or approximately true only by holding antenna gain fixed (an assumption) between the two cases. In that way the lower frequency antenna grows in size to a larger physical aperature and this produces an apparent path loss reduction by increasing capture area. That's the way it really works. Higher frequencies aren't really attenuated more by the atmosphere.

Maybe that's what you're saying

 

[Tower Guy]

Higher frequencies aren't really attenuated more by the atmosphere.

Terrain is the problem, not the atmosphere.

 

[NightHawk]

Terrain is the problem, not the atmosphere.

in what way?