As if my mobile ham station wasn’t already kooky enough, I’ve gone “full nerd” by adding four Diamond K9000 motorized antenna mounts! WHY? When my VHF rover had only three Yagis (50, 144, and 432 MHz), I was comfortable with rotating the beams and just letting the ATAS-120A’s radial drag under the lowest boom as it passed by. The shorter antennas would either barely touch or miss the lowest boom altogether. However, adding the fourth Yagi (222 MHz) reduced the clearance for my verticals. I was no longer willing to accept the collisions.
At first, I mitigated the collision risks by adding NMO antenna mounts to the hood. They’re a great option for low-mounting antennas, but not nearly as convenient as simply pressing some switches to lower all antennas at once! Later, I realized that another benefit of having the motorized mounts is that I can slip into parking structures without stopping to remove my antennas. While that may sound lazy, it’s also an unrealized benefit to fellow drivers who may be inconvenienced if I was to stop to unscrew and stow each antenna. Believe it or not, I don’t always know when I’m going to wind up in a parking garage.
Of course, having the K9000s is a fun novelty! But I also think they add a small amount of visual security. My car usually has a rooftop cargo box mounted. As a result, the black antennas tend to blend with the box when they’re lowered. This photo shows the tight fit alongside my cargo box. Sure, the lowered antennas are visible to someone who’s near the car, but they’re less noticeable at a glance or from a distance. Obviously, I remove the antennas completely if I’m going to park the car someplace where I think theft is a genuine problem (or I don’t visit that location at all). Still, the K9000 mounts give me the option to reduce the rooftop profile, even if by only a small margin. They may even provide a marginal benefit to fuel economy at highway speeds… maybe.
The K9000 does have some limitations, though. For example, it’s advertised to be compatible with “no ground plane” antennas that do not exceed 45 inches (114 cm) or 1 pound (450 g). The mount is perfect for my Diamond NR770HBNMO and CR320BNMO antennas, both of which are 38 inches tall (97 cm) and less than 1 pound. It’s also a fair fit for my WeBoost antenna, which is ~22 inches tall (56 cm, but has wind load at the top). However, Yaesu’s ATAS-120A is both too tall at 55-63 inches (140-160 cm depending on band) and too heavy at 2 pounds (900 g). Still, when has a manufacturer’s specification stopped me or others from at least trying something that we shouldn’t? 😉
Additionally, the ATAS coil tube catches a lot of wind. The extra force is enough to fold-back the antenna at highway speeds; it can even cause the plastic gearing to jump teeth. In my experience, that only happens when I exceed 70mph (113 km/h), perhaps less with a headwind. If I have the antenna extended to cover 20-40m, then the loading is greater and the antenna will lay down at lower speeds. Some have seen my ATAS laid forward as shown in this photo and asked why I chose this direction, especially since it defeats the protective spring in fold-over scenarios. The primary reason is because the whip interferes with hatchback operation when the antenna is down. The second reason is that I prefer to have the antennas stow to between the roof rack’s crossbars; the WeBoost antenna folds forward, too. Having the K9000, I opt to lower the ATAS when it’s not in use or when I plan to drive on the highway. I use a mechanical stop to support the weight of the antenna when it’s lowered.
The factory mounting flexes a little more than I prefer, possibly since I’m overloading it with the ATAS! 😀 I removed the factory brackets and drilled some Unistrut brackets to fit the bottom of each K9000. The new hardware is very sturdy and provides plenty of options for offsetting the mounts to allow the antennas to “nest” when lowered. You may have noticed the bonding straps that I’ve fastened at key points on the roof rack and K9000 mounts. They aren’t required for proper operation of the K9000s, but provide an “RF ground” to the ATAS-120A for proper tuning. All feed lines, 12V power leads, and bonding straps have sufficient slack to allow for full articulation of the K9000 mounts.
The “UP/DOWN” switch that comes with each K9000 mount, shown in the photo album below, is sufficient for a single mount. Having four, though, I wanted a solution that is less clunky, easier to activate either individually or all together, and has a cleaner 12V connection than the bulky 12V plug. I home-brewed this box from supplies acquired from Amazon. The DPDT momentary switches are labelled “2” for the dual-bander, “W” for the WeBoost antenna, and “A” for the ATAS-120A. The CR320 tri-band antenna is on the same circuit as the ATAS since neither antenna is for primary use. The “12” and “24” switches are for a battery charger and power supply. The “D” is to remind me of which way is “Down.” Pressing a switch to the “Up” direction applies properly polarized voltage to the motor while pressing to the “Down” direction reverses polarity. The factory switch grounds both K9000 electrical connections when no drive is required, but mine solution does not. Each circuit is open when its switch is in its center/neutral position.
See the photo below for more details. I even have images of an opened K9000 since I pinched a wire and needed to repair it. I don’t know the duration of Diamond Antenna’s warranty period, but I also have no doubt that my shenanigans immediately voided it anyway, as does carrying an ATAS-120A on one! 😀
Still Crushing Warranties!
Scott
