With digital OTA TV signals, a lot of things could cause you to fail to pick up a signal on any channel. First, do you have an indoor or outdoor antenna and how far are you from the transmitters for you local stations? Digital signals are either enough to for the tuner to interpret or you get no signal. Next check that the antenna is pointing at your stations' transmitters. Use antennaweb.org
to check the direction for your location. Antennaweb assumes an external antenna and provides a very conservative list of stations.
Check for buildings, hills or tall trees that might block the signal to your location.
If your antenna is providing a signal to several TVs, try a direct connection (taking out the splitter). You may need an amplified splitter to minimize the signal loss. Note: amplifiers (whether at the splitter or part of the antenna) can fail and become signal filters (blockers) instead. The direct connection tests this as well.
If another TV does pick up the signal from the antenna (at this point), then the tuner may have failed. It may also just be a weaker tuner compared to the other TV. Surges (for example, lightning strikes) can cause a tuner failure. In that case, you need a new tuner. (a stand-alone tuner like the converter boxes might work) or try a site like shopjimmy.com, searspartsdirect.com or partstore.com. SearsPartsDirect lists the tuner here: http://www.searspartsdirect.com/partsdirect/part-number/Emerson-Parts/Television-Parts/UTUNATSSP006/0057/528/Model-LC320EM9/0352/0333600?keySuffixId=NA&pathTaken=partSearch&pathRender=modelComponent&documentCompId=50034435&diagramPageId=00001&productTypeId=x&searchModelNumber=LC320EM9&subCompDesc=Lcd%20tv&brandDesc=EMERSON&modelDesc=LCD-TELEVISION&blt=11&shdMod=
This TV was made by Funai so you may see other TVs that use the same part.
I hope this helps.
(I have two TVs with different quality tuners. With one, when the antenna shifts slightly out of place, I can lose the ability to tune in the channels from the closest transmitters. The other TV does not lose the signal until the antenna rotates more than 90 degrees from its usual position.)