Firstly there is this info regarding co-ax to hdmi (I think that's what you meant). There is no such simple device You need something like a STB or PVR to convert the co-ax analogue input signal to the hdmi digital output signal. See link
An easy temporary solution is to connect your aerial into a STB (set top box)or PVR (personal video recorder) if you have one, then connect to the TV from it either via HDMI (if it has it) cable or via composite video (red/white/yellow) cable. You then have to use the STB remote control for channel/volume selection, whilst the TV is just set on the correct input source and turned on/off and perhaps the volume adjusted to suit.