Hamstick Antenna Mounted On Fiberglass Tonneau Cover

[KD5ITM]

I’m installing a fiberglass tonneau cover on my 2016 Chevy Colorado. My dual band and Hamstick antennas are going to be mounted on top of the tonneau cover. The dual band right behind the right side back glass and the Hamstick right behind the left side back glass. The majority of my HF mobile operations are on 20m using a 20m Hamstick (which I’v been using since the early 2000s with very good success), but I do have the ability to also operate 40m, 17m, 15m and 10m using Hamsticks for each band (40m being my least operated HF mobile band).

Iv been using a 20m Hamstick since around 2001 - 2002 for mobile HF with very good results. It’s very common for me to get signal reports saying that I sound like I’m running 400w - 500w into a 3 element beam at 50 ft rather then using a 20m Hamstick on the mobile with 100w.

For the ground plane, I was thinking of lining the compleat bottom side of the tonneau cover with aluminum window screen. I’m assuming that the aluminum screen needs to have a good bond with the antenna mounting bracket via the 3 mounting bolts. Does the aluminum screen also need to be bonded to the truck via a copper ground strap going from the aluminum screen to the bed of the truck. If so, do I just need 1 ground strap or is it better to use a ground strap at all 4 corners of the aluminum screen?

The first picture shows how my dual band antenna has been mounted on 2 previous trucks since the early 2000s. The Hamstick is mounted identically on the left side of the tool box. The second and third pictures show how each antenna is currently mounted on top of the new tonneau cover.

- KD5ITM -

 

[mmckenna]

I think I provided a response to all this in your other post:

2m/440 dual band tonneau cover installation

I’v mounted a Comet SBB-7 dual band antenna to the top of my trucks Leer fiberglass tonneau cover on the right side right behind the passenger side back glass using a custom made stainless steel mounting bracket. I fully understand that this installation doesn’t have the most efficient ground...

forums.radioreference.com

 

[prcguy]

I think 3 or 4 wires going from the mount to under the cover to the tailgate would suffice and attach the wires to the underside of the cover so they roll up with the cover. The current mount for your 2m/440 antenna has no ground plane at all, the antenna is hanging in space and performance/SWR will suffer. If you mount the antenna bracket to the top bed rail behind the rear window the ground plane will improve but may not even be adequate for 2m as I believe the top rail folds under and ends without touching the vertical bed wall, isolating the top rail. An HF mount on the top bed rail with wires running back under the cover should work to some extent.

 

[vagrant]

I have a Chevy Trailblazer and use VHF/UHF and HF antennas mounted to the luggage racks. Thus, the mounts are not directly mounted to holes in the metal roof. I use some flat 5/8 round rings with a hole mount point. These are placed and secured with the nut mount below the antenna.

VHF/UHF - This is a Diamond 1/2 wave NR770 antenna on a Diamond motorized mount that attaches to the front cross luggage rack. The metal roof helps as a ground plane, as would metal under your hard cover. Additionally, from the base of the antenna I ran wires to existing screws that secures the luggage rails to the roof. The base of the antenna sits four to six inches above the roof. I also tested and use a Comet CA-2x4SR antenna on that mount which is not a 1/2 wave antenna and it also works well.

HF - Here I use Lakeview Hamsticks 40, 20, 10 and six meters. I may have used other WARC band as well, but not that often. I also use a Yaesu ATAS 120A HF motorized antenna. This separate HF mount is on the rear cross luggage rack. For this mount I ran two wires to screws that hold the luggage rails down. Each wire goes to opposite sides of the SUV to the roof. A multimeter confirms the continuity at the base of the mount to different parts of the SUV, like a door latch, seat bolts, etc. Here again the metal roof is helping. The SWR is fine, although I don’t think I tried 75 meters yet. Also, those Yaesu motorized antennas are finicky and a bond is important. It will tune with that mount and operates as well as it can. It’s not the greatest antenna, but beats swapping Hamsticks in poor weather. @prcguy also made a roof bonding helper using a flat magnet sheet cut to the size of a 6x8 copper sheet. A grounding strap connects the plate to the base of the antenna mount. I have the materials and plan to build/use when stationary. Mainly to test and see if where it offers improvement. While that magnet plate would work on a metal roof, I think the multi wires suggestion above connected directly to your mount will help.

You will need to experiment at this point. This includes different material under the cover and number of wires that connect the mount to it. I would connect a wire or two directly to the truck bed as well on opposite and or all sides. Hmmm…this now has me wondering what the results would be without material right under the cover.