Realistic HTX-202 Shows Error
 

I turned on the HT after not using for a while and am getting the
message Er 1 flashing and beeping. There is nothing in the manual about
this except my own note saying to push F button and D together (clear),
then turn radio on. I don't remember this happening but it has been a
while since I used this so apparently this happened before. However, it
isn't working now. If anyone knows how to rid this of the error, I would
greatly appreciate it. Also, it's been connected to my outdoor antenna.
Could something have occurred to cause this? All of my connections are
intact. I disconnected it and used the alkaline battery pack and still
get error message. Thank you.