Can tune in station on some TVs and not on others

[Patrick T]

We got a 37 inch Toshiba HDTV in January and a UHF antenna a few weeks later. There are 9 digital stations in our area, but when we put the antenna up, we couldn't tune in 11-1. I have a computer with Media Center on it and it can tune it in. We had an antenna company come out and check out the antenna and they determined the antenna was working. We figured there was something wrong with the TV's tuner and took it in for repair and now have a TV on loan while it is being fixed. It is a 26 inch Toshiba and it pulls in all of the stations.

Yesterday, we got 2 DTV converter boxes for 2 analog TVs in the house. Neither will pull in 11-1 during the day. I scanned for channels late at night and they both were able to receive it, but by 9 AM this morning, they wouldn't again.

There is a 4 way splitter in the basement that all TVs run off of, but taking other TVs off of it doesn't make a difference.

Why would some TVs tune in the station while others cannot?

[eakes]

What you are seeing is the difference in sensitivity between receivers. You 11-1 channel is apparently a weak station. If it were analog you could possibly see a picture but it would have a lot of noise (snow). With a digital signal one does not see snow in the picture. When the signal is weak there is a very fine line between picture and no picture. What you could try is to bypass (merely disconnected the other lines does not help) the splitter and see if the converter boxes will work, or take one of the converters to the basement and connect it to the line feeding the splitter (no splitter in the line). If there is sufficient signal without the splitter in the circuit it should be possible to use a distribution amplifier in lieu of or ahead of the splitter to deliver a useable signal to all TVs. I have used a RadioShack distribution amp for years for this purpose, it has four outputs.

[Patrick T]

OK, I gave some wrong information before. Sorry about that. It isn't just a splitter in the basement, but an amp. It says 10dB, 50-450 MHz on it. There is also a booster on the roof antenna, which is on top of a 2 1/2 story house.

The TV and computer both show 11-1 signal as being very strong, but I have read on here that you can't necessarily rely on that. The tower for 11-1 is in the same direction as the other TV stations in the area, so I know the antenna is pointed in the right direction.

Why can the converter boxes tune the station in late at night, but not during the day?

[Scott in FL]

Do you know for sure that the digital stations in your area are all UHF? Some might be VHF. You can check by entering your zip code into tvfool.com. This will also tell you if any of your digital channels will change frequencies after the February 2009 transition.

Also, your splitter/distribution amp in the basement is only rated to 450 MHz. That's VHF only (no UHF).

As another person pointed out, different tuners have different specs. But first, if I were you I'd replace that distribution amp in the basement with a passive splitter (rated to 900 MHz).

[Patrick T]

Yes, I'm sure it is UHF. The physical channel is actually 44.

OK, I can replace that amp in the basement. That's a good place to start and hopefully that will fix the problem!

[eakes]

OK! Considering the new info I need to change a few things from my original response. With the pre-amp at the antenna, the distribution amp is likely doing more harm than good, especially since it is not rated for UHF frequencies. As Scott suggested, replace it with an appropriate splitter. Caution: make sure the power insert for the pre-amp it on the antenna side of the splitter.
Although this is not the case here, in general, too much 'amp' is sometimes worse than not enough. Unwanted signals and noise get amplified to the point that the receiver front end can be overloaded resulting in poorer performance for desired signals.
In this case, the distribution amp does not have the proper rating to function at UHF. In fact it is probably downgrading the 11-1 signal. Without the amp I would expect 11-1 to be received by all your tuners.

As to why reception is better at night: Changing atmospheric conditions affect the amount of signal that arrives at the antenna. Generally, conditions are better at night and in your case a higher usable signal is available from 11-1 during night time hours when compare to daytime.

[paulman182]

I'm pretty sure the frequency for channel 44 is in the 650MHz range, which puts it outside the range of the amp/splitter.

[Patrick T]

That seems to have done the trick. I replaced the amp with a 4 way splitter rated up to 1000 MHz and we are now getting 11-1. I feared we may lose NBC next year, so I'm glad this was such an easy fix.

Thanks, everyone!