Good question.
In some cases, I have this question myself.
There may not be an easy way to tell.
Most TVs are not labeled. I have used the following link to get information about digital television. http://www.dtv.gov/consumercorner.html #faq6
The bottom line is, if you don’t have the television user manual and are not certain of the televisions production date, you probably won’t know until the digital switchover takes place. To make matters worse, RV manufacturers typically buy items in bulk months or even years ahead of time. This means your television could be one or two years older than your RV!
Televisions are not specifically built for RVs. Once analog signals are turned off, you will need a digital converter for each television that does not already have a built in digital tuner. It is possible to share one digital converter if your RV has an antenna switching box however, having only one digital converter connected will allow all the televisions connected in series to receive the same channel at one time. This will work fine if you only watch one television at a time or if you want more than one television on the same channel. Sometimes tailgaters have several televisions tuned to the same channel throughout the RV or outside. Having one digital converter connected at the switching box is ideal for this scenario. Digital converters use an infrared remote control. Infrared remotes require a direct line of site to operate. Be certain you have a direct line of site to each digital converter from your viewing area. Line of site is necessary with a digital converter in order to change channels.
To be able to receive the antenna signal separately at each television, you will need a digital converter for each television. This can be a problem in an RV. Typically the main television is near a cabinet that contains an antenna switching box, a VCR or DVD player and possibly some other devices. This cabinet is a good location for a digital converter. The converter has a coaxial cable input and output. The coax from the antenna connects to the input. The coax to the television connects to the output. To use a digital converter for each television, connect the digital converter after the antenna switching box. This means the connector labeled “out to TV” will be connected to the digital converter input. The digital converter output is connected directly to the TV. The digital converter has a switch on the back labeled “Channel 3 or 4” This switch needs to be in sync with the TV. Once the digital converter is powered up and connected to the TV, it will function as the TV tuner. The TV will remain on channel 3 or 4 and the stations will be changed with the digital converter remote.
Finding a location near each television in an RV can be a problem. The digital converter requires a 120 volt power connection. There will be an outlet where the TV is located, but it may not be accessible. You may need professional installation if you cannot access the outlet and coaxial cables. In many cases the TV may have to be removed to access the connections. In any case, the digital converter must be located near the TV and in a direct line of site to the user for the remote to work. I have custom installed digital converters in RV bedrooms. Each installation is different and some are difficult. I have mounted the converter boxes in a variety of locations. Fastening under a hanging cabinet is one idea. Mounting beside the TV cabinet on a wall or flat surface may be possible.
Another concern I have with digital converter boxes is reception. My own personal experience to this point has been that TVs connected to a digital converter do not receive stations as well as TVs connected directly to an antenna. Sometimes a weak analog signal can be received resulting in a picture with static or a snowy picture. These weak signals may not strong enough to even be detected by a digital converter. When the digital converter does not receive a strong enough signal, you will get no reception at all. On the positive side, it is possible to receive far more stations when than analog when the signal is strong. Typically with campsites being in remote areas, the signal is weak.
Having a DC (12 volt) powered TV will no longer be useful. Digital converters must be powered by AC (120 volt). Without the converter, you won’t receive stations. An inverter could be used to power a digital converter when AC (120 volt) power is not available.
Of course, all this talk about digital converters only matters if you are trying to receive television channels from an antenna. Satellite and cable work without a converter or digital TV.