Adding a second antenna

[jnojr]

Given this roofline & antenna (Comet X50NA), where could a GMRS J-pole go? Someone suggested it could go on the same mast, just lower than the Comet. But the install instructions for the J-pole say to make sure the top of the mast is not higher than the T connector, which would put it right next to the Comet.
I'm thinking another mount like https://www.amazon.com/gp/product/B0B217C418/ Does it have to be a certain distance away from or below the Comet?

 

[mmckenna]

It can be below the top of the mast, it just needs to be stood off a few feet so the mast doesn't detune the antenna, or act as a reflector and make it directional.

You can fabricate your own bracket using a two lengths of Unistrut and some appropriately sized clamps.

You do not want the GMRS antenna at the same level as the X-50, as there will be too much coupling between the two antennas when you transmit.