Diamond X-200 High and Low SWR Issue

[WeldGuy]

I helped install a new Diamond X-200 dual bander for a friend yesterday. It sits on a 20 foot mast, clear of any nearby obstructions attached to a one story house. There is a short run of new LMR400 coax from the mast through the wall of the shack. New connectors were used and checked for continuity.
When we checked SWR at 5 Watts on 2M, we got above 2:1 across the band... nothing under.
When we checked SWR on UHF it was a near-perfect 1:1. There appear to be no provisions for tuning other than cut or add material. What thd heck js going on???

 

[jwt873]

You probably did this... but just in case..

Did you connect the upper and lower elements? The antenna comes apart into two sections to make it easier to ship. Each section has its own element. You have to fasten the upper and lower elements together before you screw the two plastic pieces together. There's a connector arrangement with a screw for this purpose.

 

[WeldGuy]

I was doing the mast... I'll check with my friend who assembled the antenna.

 

[doctordialtone]

I'll check with my friend who assembled the antenna.

https://www.diamondantenna.net/pdfdocs/X200A%20Instructions.pdf

 

[WeldGuy]

He said he assembled it exactly with instructions. He's done many antennas.
The only thing I question about the installation was not adding a ground to the mast. The owner felt the mast being pushed into the ground was enough (I know, I know)

 

[prcguy]

I would double check with an antenna analyzer to rule out error in the SWR meter. Grounding the antenna will have zero effect on the match but its required by code. Check NEC Article 810.

 

[jwt873]

OK... If he had the instructions in front of him, he would have seen the procedure for connecting the internal elements..

As prcguy points out, if you have access to an analyzer you can determine how far out it is. There's no way to adjust the antenna that I know of. (not to say that there isn't). Best bet would be to get in touch with Diamond.

 

[WeldGuy]

UPDATE: I called Diamond and spoke with Wayne... wow, what a wealth of knowledge!
He also questioned the connection point of the lower and upper sections. He listed a few other things that could be causing the problem.
We will return to our friend's house next week and go through the list of suggestions Wayne provided. He even suggested we call him with everything in front of us if we are unable to find the problem. Great Customer Support!
I'l follow up here so others may learn from our troubleshooting efforts.
Thanks to those who offered suggestions.

 

[Ubbe]

If you google you'll find some people that have high SWR on 2m with this antenna. Two antennas doesn't measure the same so it seems to be a quality problem at the factory. I took my Diamonds X510 and F23 apart and the capacitors soldered to the loading coil at the bottom where placed so that they touched the coil and ground and had their component legs so stretched that any mechanical movement would crack the capacitor.

Repair a Diamond X200 VHF/UHF antenna | ON3JT

Attempt to repair the Diamond X200 VHF-UHF antenna faulty capacitors

on3jt.byze.be

/Ubbe

 

[WeldGuy]

OK... It's FIXED! Indeed, it was the center conductor, set screw between the top and bottom sections of the antenna.
We returned today and lowered the mast. Pointing to the set screw on the antenna instructions, the person who assembled the antenna last week didn't remember seeing a set screw. We disassembled the top and bottom sections and found the inner conductor of the antenna was pushed up inside the upper section and stuck there. We had to tap the upper section on the ground to get the inner conductor to drop down, revealing the set screw.
After properly reassembling the antenna, SWR was 1.4:1 and lower across the band.
Thanks to all who made suggestions.