Can I use this old ChannelMaster antenna wallplate with Digital Antenna?
There is a lot of miss information out there concerning TV antennas and it mostly caused by marketing hype. Rabbit ears tv antennas made 50 years ago will pick up  broadcast from a  TV tower broadcasting a digital signal today if it is close enough. There are differences in quality and types, ( directional vs omni - directional- UHF, VHF etc. ). I currently have a set of rabbit ears with one of the "ears" broke off and piece of tinfoil ( it use to be my tinfoil hat ) attached and i get all the digital signals HD and non HD in my area.

It is all about placement, direction and distance. 

some reading for those interested. 

NO such thing as an HDTV antenna   

10 things you need to know about Digital TV Antennas

All About Over-The-Air Antennas