[BC] mystery McMartian antenna

[John Lyles]

I have an antenna that is marked with McMartin's name on it. It is about 
20 inches long, 1 1/4 inches diameter and is a green glass-epoxy 
cylinder. The connector on one end is a type F. I popped the nylon plug 
on one end and it might be a helix (coiled) antenna. I am guessing it is 
  for RPU due to size, but I'd like to know for sure. I suppose it could 
be an FM antenna also, for SCA. I haven't swept it on network analyzer, 
thought I would ask here first. What freq? Any ideas?
Thanks
John Lyles