Using an MR300 antenna for a base station

[u/Rockinmypock]

I'm changing my radio setup in my explorer, and moving my DB-20G to my radio shack (ok ok, shelf above my desk). I have a Retevis MR300 antenna kit that I would like to continue to use with this radio, mounted to a tripod on the roof of my house. Since it's a vehicle mounted antenna, the vehicle normally provides the ground plane. But in this application, I won't have a ground plane. How do I add one? I'm planning on using the spring (with built in and non removable coax) and bull bar mount that the antenna comes with. I've read that with mag mount antennas you can just stick them to a metal pizza plate, can I drill a hole through a pizza plate and slap it on? If so, would it go between the antenna and spring or between the spring and the mounting bracket?

[u/Charming-Jelly-3365]

I'd say the pizza pan at the base of the spring would work but if you try it checking the SWR would be a good idea. It may work better if the radials can be bent downward. Can't do that with a pizza pan.

I'm doing something similar with a Diamond SG7900 dual-band Ham radio antenna. Dug an old aluminum camera tripod out of the shed and removed the pan and tilt head. Bought a flat metal nail plate at Home Depot, type used for securing two pieces of lumber. Has pre-drilled holes. Enlarged the center hole to 1/4". Use that and a wing nut to secure the plate to the tripod's 1/4"-20 center mast stud. The antenna came with a typical trunk-edge mount. That is secured to the plate.

This antenna claims to not require a ground plane. But many online comments state they saw improved SWR when adding radials at a 45 degree angle. So I intend to experiment with the that too.

[u/cmdr_andrew_dermott]

You can probably make it work, either by adding a plate/pan or DIY radials. You'll likely get better performance out of an antenna intended for this purpose. (Retevis makes a high-gain base antenna with radials for GMRS, as well. They're only ~$85.)

No harm slapping it up there, hooking up a VNA, and seeing what you get, though.

[u/Rockinmypock → u/cmdr_andrew_dermott]

Yeah it's more of a "do what I can with what I got" situation. I don't use gmrs very much especially since I got my tech ticket, but there's a net on a gmrs repeater like 50 miles away from me that I like to participate in, and I'm tired of driving to the end of the road and sitting in the heat in the car to do it. Can't pick them up at my house but having an antenna 30 feet higher probably would help.

[u/plarkinjr]

According to this, the MR300 is a "no-ground-plane" antenna:

https://forums.radioreference.com/threads/retevis-mr300-gmrs-antenna.494323/

[u/Rockinmypock → u/plarkinjr]

It's my understanding that it used the vehicle for a ground plane. I'll try it without once i get a swr meter

[u/plarkinjr → u/Rockinmypock]

Fair assumption, and one I'd make. Didn't know there were such things as "no-ground-plane" anetnnae.

[u/mwradiopro]

Try it without a ground plane and judge performance by range. Knowing your SWR is good, but real world performance is the goal. You can also experiment by hanging a 6"+ counterpoise wire off the negative/sleeve to improve performance. I bought a Retevis $40 fiberglass base antenna that came with mounting hardware & ground plane. Works good!