SWR issues

[fadec]

In a dual antenna system, with everything properly grounded I still get high SWR readings. Though when I grab the right antenna at the base the SWR will fall to around 1.1 or so. (touching the left has not effect either good or bad.) My antenna's have "balancing" ground wires on the antenna, hooking one or both up to a ground only makes things worse.

What can I do to replicate "me" touching the right antenna base to reproduce a good SWR reading? Am I acting as load or ground on the antenna when I touch the base?

I am running a Jeep CJ-7 with dual antenna's on the rear bumper in the ONLY location that can be used. (this is a custom rock crawler and mounting locations are very limited.)

 

[thunderbritches174]

Do away with duals and run single. Duals normally require a 1/4 wave length separation(102 inches). If you desire the dual look just run a single coax to one antenna and go from there.

 

[DX949]

In a dual antenna system, with everything properly grounded I still get high SWR readings. Though when I grab the right antenna at the base the SWR will fall to around 1.1 or so. (touching the left has not effect either good or bad.) My antenna's have "balancing" ground wires on the antenna, hooking one or both up to a ground only makes things worse.

What can I do to replicate "me" touching the right antenna base to reproduce a good SWR reading? Am I acting as load or ground on the antenna when I touch the base?

I am running a Jeep CJ-7 with dual antenna's on the rear bumper in the ONLY location that can be used. (this is a custom rock crawler and mounting locations are very limited.)

Put one on top and the other on the belly of your rock crawler,so when you flip it you'll still be able to call for help or assistance ;0)

 

[KD0LWU]

Duals are a pain to get right, one may resonate, the other wont, might be a bad splice in the coax, might be shorting on one side of the coax split. When you are holding it you are creating an inductance, much like a coil would, I'd swap them side to side and see if follows the antenna or stays on the base.
I agree with the other poster though, I'd go with a single and eliminate a lot of problems! In your application I'd run a 102" stainless whip and be happy.

 

[poikaa]

An offset tuning stub would cure the problem but it a trial and error thing.... Best to go for one antenna as it is easier to deal with. For looks the second can be a dummy.

73 poikaa

 

[fadec]

Thanks guys. I'll give the single antenna a try.

 

[SCPD]

dual antennas

i was wondering if your using 75 ohm coax, not 50 ohm like a single antenna requires, this would cuase high swr's, and with dual's you need about 8 feet of space between antenna's for proper radiation