My trailer-mounted tower was a success during ARRL’s January VHF contest. Unfortunately, there was one area in which it fell short: AGILITY. Sure, the trailer works fine when my goal is to proceed to a destination, park, and operate. On the other hand, agility is very helpful when working grid lines with other rovers. We tend to skip back and forth across the grid lines to maximize our points multipliers. I can be quite the wizard at maneuvering my small trailer during the day. See my “Stunt Parking“ page for details. However, things change for the worse when I need to back the small black trailer in the dark, especially in unlighted areas. As a result, I very quickly returned to a rooftop setup after the contest.
Given the fatigue to internal roof rack parts with my previous rooftop tower, I had two goals when returning to the roof: 1) Shorten the setup by 12-18 inches; 2) lighten the load. I started by cutting 18 inches from my tower’s mast. That alone removed one pound of topside weight and reduced the leverage that would be applied to the rack’s towers. I also wanted to find a purpose-built solution that would mimic the 22-inch “micro tower” that I had previously built. I dug deeper into Rohn’s catalog of 25G-series tower parts and decided to use their BPC25G Base Plate and BAS25G Rotor/Accessory Shelf (combined weight of 28 lbs). I found that 3 Star Inc provided the best pricing, availability, and they’re just an hour up the road, which saved on shipping costs.
I thought that returning to a shorter tower would reduce topside weight further; however, that didn’t turn out to be the case. Although the combination of the two parts is the same 22-inch height as my original rooftop micro-tower, it also features an additional shelf for the rotator; so, it’s about as heavy as the 38-inch tower that it replaced. Perhaps negating the topside weight savings that I had achieved when I cut the mast, the rotator shelf sits about six inches higher than previous designs. All is not lost, though. I’m aware of the extra stresses applied by the tower, which will alter my driving habits, and still have managed to reduce the overall height by about 12 inches. I haven’t struck any tree branches during the 2000 miles of road testing so far. So, I’m optimistic about its future.
You may have noticed the absence of the 6m horizontal loop antenna by M2Inc. When I shortened the mast, I also introduced a collision hazard between the 6m loop and the lowest Yagi. This hazard will be exaggerated when I eventually add a “Rover Special“ Yagi for 222 Mhz, which will push my 432 MHz Yagi down by about 10 inches. Since I also added a 222 MHz M2Inc loop, I extended my “Loop Module” and opted to mount the 144, 222, and 432 MHz loops at the same level. I also return the 6m loop to the module when the tower is not mounted.
Some Rovers argue that they have no need for loop antennas once they have Yagis available to them. K2EZ and I have noticed that there are times when we can hear stations on a loop, but not the applicable Yagi. That means that the Yagi is turned away from the calling station. That could be a sign that the Yagis need to be turned around. But, if I can work a station on a loop, then why would I bother with trying to pinpoint their direction with a Yagi? Or, as an alternative, I’m now aware of the station and can turn the Yagis to fine-tune them for the higher bands. I’m still testing the concept.
The ATAS-120A and a new CR320 tri-bander, which is currently my primary antenna for 223 MHz FM, are also collision hazards for the Yagis. They both normally ride on the passenger side of the roof rack. Realistically, I don’t mount my ATAS-120A while operating with the Yagis. However, I want the option to work someone on 6m FM (52 MHz) and 1.25m FM (223 MHz) during contests. So, I moved those bands to the hood, currently only during contests. I did not use traditional lip mounts to achieve this. Instead, I used “ditch light” brackets, which are popular in the overlanding community. I have a full write-up about this modification shared HERE.
As with my previous setup, the tower is mounted on three Superstrut bars, two of which are for primary support and the third is to support a fold-over feature. I use a fourth Superstrut to provide a resting place for the tower when it is tilted. The fold-over feature is not necessarily fast because of my feed line routing, but it’s an easier way to address problems on the top antennas than removing the entire setup. The tower, rotator, mast, feed lines, and Yagis weigh a combined 70 lbs. I can lift and carry 70 lbs, but it isn’t very fun in such a tall and unwieldy package, especially if the wind is blowing. Tilting the tower allows me to remove the mast and Yagis as one 25-pound unit, and then the remaining pieces as smaller parts that are lighter and easier to manage. Setup takes about an hour since I need to dress and ziptie the feed lines and rotator control cable; tear-down can happen in less than 30 minutes. Removing the Superstruts adds 10-15 minutes to tear-down time, but I can also leave them in place full-time with only a minor fuel economy penalty. All Superstrut is attached to the crossbars using Yakima’s M10 T-bolt. See a photo in the album at the bottom of this page.
Speaking of fuel economy, I’m frequently asked about aerodynamics and fuel economy. The difference really isn’t terrible. With a naked roof (no rack, only a dual-band antenna mounted), it’s fairly easy for me to average 35 mpg. The car is rated for 24/34 mpg (28 mpg combined). At home and with my usual roof rack load, I usually see between 25-29 mpg, depending on my AC use and how much I idle the engine during radio events. With the tower, three Yagis, three loops, and eight vertical antennas (including the Scorpion with caphat) my trip to and from HamCation in Orlando averaged 25 mpg! That was 1620 miles driven with 64.7 gallons of fuel used. Most of the SUVs and pick up trucks that people think I should be driving struggle to achieve that without a payload at all! I think my little GTI is doing just fine. 🙂 See the lifetime fuel economy graph with milestones below. See more photos of my setup in the album below, too.
Have Radio Station, Will Travel!
Scott, KE4WMF
