Today, I'm excited about the 3/8-24 thread standard that we use for antenna's. I have no idea how this standard came about, or even if it's really the ideal thread and bolt size for our service's application, but I'm still pumped about it. Why is that? Because it makes playing around easier when parts made by different manufacturers fit together! In my case, I'm thankful for it, because it let me play around, and use parts from my Buddipole Antenna in my mobile mount while I activated Hopewell Furnace for National Parks on the Air.
For this arrangement I put 2 of the 11 inch arms together, screwed them into the mount on my trunk, followed by the coil, and then one of the telescoping whips to top it off. Because I was shooting for the 20 meter band, and I wanted as much efficiency as possible, I basically started with the telescoping part fully extended, and the tap on the coil set to jump over pretty much the entire coil - this made the antenna resonant a frequency higher than 20 meters, meaning the antenna was electrically to short. To "lengthen" the antenna I just adjusted the coil by moving the tap down (physically) a couple windings at a time, until I found the point where one tap made the antenna just a little to short, and the next tap made it just a little too long.
- It ended up being a slightly longer antenna than the hamstick. More antenna element and less coil generally makes for a more efficient antenna, all else being equal.
- The coil for the Buddipole has a much larger diameter and more spacing between windings than the tiny wire tightly wound around the fiberglass rod inside the hamstick. A Bigger coil, bigger wire, more space between windings also generally makes for a more efficient antenna.
- The diameter of the antenna element is larger, so in theory this should also be more broad-banded than the hamstick.
Now, for 20 meters, I'd probably be even better off with something that can be full size, with no coil, like this little number from MFJ (17' telescoping whip), but since I don't have one of these, I'll just make what I have work. At some point I plan on grabbing a couple of these at it would definitely help give me more flexibility with my portable antenna stuff. Once I do, I'll be sure to share what I find as I play around with it.
Playing around with this arrangement also made me realize that I have a couple other options that should work better than my hamsticks too (when I'm parked anyway - I'm not about to use this while going 70mph down the highway, I have no idea what wind loads the Buddipole parts where designed to handle!) The first and most obvious would be to use the same arrangement, but with the tap on different spots of the coil to use it for 6, 10, 12, 15, 17, 30, and 40 meters. I also realized that it "might" work to put both coils in a row, one after the other, to use it on 80 meters - I'll let you know how that works out when I have time to try it.