Roku setup

[e-m-]

Why have I lost the signal for live tv stations 2.1, 33.1, 33.3, 36.1, & 36.2.  I now get a "No Signal" note when I try to open them up.  Also, Roku movies are very dark for night scenes.  Daytime scenes are normal.  I'm thinking of returning the tv and purchasing a Vizio tv.  

[atc98092]

Local stations sometimes change the RF channel that broadcast on, and you need to rescan for channels. The Roku OS doesn't have a way to manually enter the RF channel to view then save, unfortunately. 

Remember with the change to digital TV broadcasting back in 2006 (ATSC 1.0) channels are no longer always on the RF channel that you knew them from on the analog spectrum. Here in the Seattle area, there's only a few stations that call themselves by the actual RF channel number they now broadcast on. For example, our local ABC, NBC and CBS stations still call themselves channel 4,5 and 7, but in reality they broadcast on RF 30, 25 and 23. 

Also, if they did change the RF channel they use, it's possible the antenna you are using might not be optimized for the channel they now use. Back in the analog days, here we had almost no stations in the UHF band (channel 14 and higher). A VHF antenna that works fine for channels 2-13 might not do the job for the higher channels. For a brief education: channels 2-6 are considered Low VHF, broadcasting from 54-88 MHz (just below FM broadcast). Channels 7-13 are High VHF are from 174-216 MHz. This is actually quite a step above Low VHF, and in some cases even these need a different antenna design compared to Low VHF. UHF TV channels run from 470-806 MHz. As the frequency goes higher, the wavelength of the broadcast gets smaller and harder to receive. That's why the antenna you're using might need to be very different than what you used 20 years ago. And it really depends on the channel used by each of the stations you want to watch. 

The best tool to determine what you need for an antenna is a web site called Antennaweb.org. You enter your home address and it returns a list of stations you should be able to receive, information about each of those stations (such as their real RF channel) and what sort of antenna you might need to receive them. The web site is completely free to use and offers a wealth of information about broadcast TV.