Digital Television Reception

This was the first weekend since the analog television transmission was shut off that I had a chance to see how the digital signals come in at the lake in central Wisconsin that we camp at (camp in the trailer/running water/electricty sense).  First, this is a remote area, and everyone had large roof mounted antennas to get spotty at best analog reception.  Some stations came in pretty good, but most were fuzzy or not available at all.  Our trailer does not have a roof mounted antenna, so I didn't try with one of those, but I did purchase an indoor amplified antenna to try out.  The results were not promising.  I was able to get some channels in and when channels come in they are crystal clear and beautiful, but for the most part I get no signal.  Also, the reception varied greatly by time of day.  Obviously I don't have much data to go on yet, but channels that worked in the afternoon were gone at night, and channels that were not available in the afternoon were there at night.  Also, some of the channels I got were quite distant (not the local channels for the area, but big city channels further away).  Putting the antenna outside and running a cable in gave slightly better results in that more channels were found, but they still were not watchable.  I don't know much about digital television on the broadcast end, so my mission now is to learn some things and see if I can improve my reception.

The Basics:

 1. Analog and digital broadcasts use the same frequency assignments for physical channels.  However, the actual broadcast frequency of digital is a little more complicated.  The digital broadcast can tell the tuner its channel number.  This is a virtual channel number and may have no resemblance to the actual channel number of the frequency that it is operating on.  The reason for this was so that a station broadcasting on analog channel 2 could then have the digital version of their station, which would have had to be broadcast on a different physical frequency band channel, show up on the TV as channel 2.x and avoid confusing consumers.  This has a couple of important implications now that the switch to digital has been made - first you can't just tune your TV to a channel you think you know exists and have it try to receive the channel, unless the receiver is smart enough to look at all the frequencies for that virtual channel.  Ideally you would look up the actual frequency that the channel of interest is broadcasting on, tune your TV to that channel, your TV would find the channel and then it would show up on the screen as the virtual channel number.  Or you use the autoscan feature of your receiver to find all the channels and the mappings.  Unfortunately if you live on the edge of reception, autoscan will sometimes find some channels and sometimes find others, and you'll constantly need to run the autoscan.  Or painstakingly go through and set up all the channel mappings manually and hope they're stored in flash or that the power never goes out!

There is a web site that can tell you the actual frequency assignments for TV stations in a given area at www.antennapoint.com.

Here are some of interest to me:

some other useful links that I discovered:

• FCC DTV Maps
• FCC Channel to Frequency Mapping
• FCC Antenna and DTV Page
• Antennaweb.org

Since I wrote this article I have also tried the same amplified antenna at my house in the city and I am getting basically perfect reception on all of the channels I expect to get.  So to improve reception at the trailer, a better antenna will be necessary.  Now the key is to figure out how to construct such an antenna (or where to get one).  I know many other people in that trailer park have very big roof mounted antennas and aren't getting much better reception than I was able to get with the small indoor amplified antenna placed outside.  Hopefully there will be more to follow on this topic.