Using the homemade 12v remote electronics available on the web and an electric car antenna, a retired gun that goes up and down is relatively easy to construct. I have never used gate actuators but they will probably work as well.
Below is a link to where I got the electronics for my retired gunner (2000 m range), and I requested that it work for 5 amp device to work car antenna and it wasn't any extra $$$.
Use a 12v gel cell battery, similar to a robo duck battery just 12v rather than 6 v so you don't have to haul a car battery around to work it. Below is a link to where I got mine:
I used a piece of pvc to support the antenna (similar to Malcolm).