BUDDIPOLE POWERmini USB connected to a 5 Watt solar panel, 3AH Bioenno battery, with the IC-705.
The BUDDIPOLE POWERmini (BPM) is basically a solar controller. Like many solar controllers, it is able to have loads like powering your radio and has the ability to power a USB device. However, the BPM has Anderson Powerpoles; these connections have become the de facto standard for the amateur Ham community. This coupled with the compact format, the data information provided, and flexibility of charging different battery chemistries makes the BPM a powerful tool for field operations.
This was my first January VHF contest from ARRL. I was very excited to do the contest for it gave me an opportunity to see how the IC-705 performed as a VHF/UHF radio. I also wanted to use the bud dipole Powermini controller with the PowerFilm solar panel to have a portable power source. During the contest I learned very quickly that I was over my head and needed to do more research.
About three months ago, I created my first 7MHz Shorten End Fed Half Wave Antenna (SEFHWA) prototype. The main feature of a SEFHWA is its coil. This allows the length of the antenna to be shorter and thus more compact. Allowing me to use it in the field when space is limited. For about three months, the antenna was doing great. It went through a few rain storms, several Santa Ana winds. Unfortunately, the antenna failed at its weakest point – the ends of the coil.
Based on what I’ve read so far on antenna theory, the shorter the wire the bigger the band. Although, is cutting the wire proportionately linear? To test this idea, I’m going to adjust a 40 meter End Fed Half Wave Antenna (EFHW). The wire size to resonates 40 meters (7.2 MHz) is 65 feet; the height of a 5 story building! To calculate the wire size, I used the following formula.
L = 468/ƒ
Where L is the length of the wire in feet, ƒ is the frequency you want the antenna to resonate the best, and 468 is a constant with velocity and conversion factors. This is the same formula to calculate the length of a dipole. By placing 7.2 for the frequency, I calculate the size of the antenna wire to be 65 feet long.
For the wire, I used the sotabeams.com antenna wire (DEF 61-12 Pt 6). I approximately measured 65 feet and added approximately 1 foot more. Adding one more foot, gives me assurances that the antenna will resonate at a lower band so I may cut the wire shorter and adjust as needed.
The End Fed Half Wave (EFHW) antenna for 10 and 20 meters is about 32 feet long. I want to create a shorten version of this antenna which will allow me to deploy the antenna easier as well as have a smaller footprint when I’m in the field. First I will have to find the specifications for a shorten 20 EFHW antenna. I hope to find it with some Ham Radio Facebook groups. Second, I will have to build a prototype. Fortunately, I have built a 10-20-40 Shorten EFHW, which works adequately for my needs, but I don’t know how efficient it is. Lastly, I will need to use the antenna in the field instead at home. Testing in the field will give me less interference with home appliances.
