DTV signal / reception?

[ejc]

I have 3 HDTV's... 17", 26", and a 52"...The 26" and 52" receive many DTV stations, including some HD stations. But my 17" receives far less DTV stations and no HD....Can you tell me why?
ps...... All tv's have CATV

pss...... About 2 weeks ago, the 17" received the same stations as the other 2.
Thanks