Regular readers of this blog know that my homebrew 19-ft vertical is my go-to antenna for “stationary-mobile” operations. I use a low-tech mounting system in the bed of my truck involving a plastic milk crate, a cargo bar, and some bungees. When we go on our annual vacation to North Carolina, unfortunately, I have to remove the crate to free up storage space. I plan to activate a park or two while on vacation this year, so I wanted to come up with an alternate antenna arrangement.
I bought the GRA-7350TC antenna with this specific scenario in mind. Previously, I tested this antenna with a magnetic mount that I had stashed away in the basement. Although a couple of successful POTA activations proved its viability, I wanted something better than my little mag mount.
Browsing around on Amazon, I found a stainless steel bracket with an SO-239 to ⅜-24 mount. I was reluctant to drill holes in my truck, but I thought a couple of small holes in the truck’s bed wouldn’t be too bad. So, I placed an order.
The bracket arrived the next day. It’s really heavy-duty and possibly overkill for my application. My local hardware store had an excellent selection of stainless steel hardware. I bought some #12 x 1-inch sheet metal screws and some star washers.
The next step was figuring out exactly where to mount it. I had to make sure that I could still close the truck bed cover without hitting it. By dumb luck, I chose a spot where I could use one of the screws that fastens the truck’s bed liner. This placed the mount close to where I wanted it. Then, it was a quick task to drill pilot holes for the three additional screws. Mechanically, it felt solid, and an ohmmeter check confirmed continuity to the truck’s body.
I gave the new mount a trial run at Ridley Creek State Park (K-1414, KFF-1414). It took me about a minute to get the antenna set up on the mount, and it was a perfect fit. I ran an 18-foot length of RG-8x coax (much longer than I really needed) to the Penntek TR-35 inside my truck.
Using an antenna analyzer, I first tuned it up on the 40M band. I couldn’t get the SWR down below 2:1. This also happened when using the antenna on a magnetic mount, too. I’m guessing a different length of coax or a counterpoise wire might help. In any event, I tuned the antenna to resonance and used a tuner to keep the rig happy. The first QSO was a station in Georgia who gave me a decent signal report.
The SWR on 30M was a bit lower but still above 2:1. Again, I had no problems making contacts with the antenna. On 20M and 17M, the SWR was down to about 1.2:1 or thereabouts.
Despite the time spent fiddling with the antenna, I logged 13 contacts, with three park-to-park QSOs. I also worked W1HNJ on 40M and 30M. As part of Museum Ship Weekend, they were operating the radio console from the hospital ship, SS Hope. The radio console is now part of the Chatham Marconi-RCA Wireless Museum on Cape Cod, Massachusetts.
I still have some tinkering to do, but I think the mounting bracket will work just fine. I won’t be retiring my homebrew vertical anytime soon, but the GRA-7350TC gives me another option when the need arises.
73, Craig WB3GCK