ULTIMAX 100 end‑fed for mobile van use

[make it count]

I've been trying to install an Ultimax 100 end‑fed antenna on my 2024 camper van. Does it need a counterpoise wire or can the vehicle body act as the ground plane or something? I've done setups on houses but never tried end‑fed on an aluminum panel like this.

 

[theDix3r]

A counterpoise is definitely recommended for an end-fed antenna on a vehicle like your camper van!
While the aluminum body can offer some capacitive coupling to ground, it's not a true ground plane in the way a residential setup with radials would be.
A dedicated counterpoise wire or multiple resonant ones will significantly improve the antenna's efficiency and radiation pattern, giving you much better performance than relying solely on the vehicle body.
You'll likely see a higher SWR and less effective radiation without it!

 

[American psycho]

With an end fed antenna like the Ultimax 100 on a camper van, the vehicle body usually acts as your counterpoise or ground plane, especially since it's aluminum, you probably don't need a separate counterpoise wire like you would on a house setup, the antenna has to be mounted well and has a good electrical connection to the van's body

 

[Parod]

If you're trusting an aluminum camper van body as a solid RF ground, you might as well believe in flat Earth theory, just run the damn counterpoise wire and quit playing ham radio roulette.