Tuning HF2V Vertical

I have the week off between Christmas and New Years Day. So I’ve added a bunch of projects to my to-d0 list. One of those was to rework and retune my Butternut HF2V. The connection had been a bit intermittent and the SWR had climbed enough to warrant use of the K3’s tuner, which isn’t at all typical of my experience with this vertical.

The installation is in my side yard, which keeps it out of the vision of she who must be obeyed and it seems to work fairly well in that location. I’ve installed a number of radials including a couple for 80 meters, several for 40 meters, and a few that just fit into the space on the side yard. I’ve also installed the kit to add 30 meters, which requires an 11 foot tuning stub made from RG-11 A/U. Finally, I’ve added a lightning arrestor and a 1:1 balun at the base. The feedline is underground in PVC pipe and comes up right at the base of the vertical. I’ve also installed a 6 foot ground rod at the base. You can see a photo nearby.

For my rework I decided to replace the 11 foot section of 75 ohm coax, make sure all the fittings are making contact, and retune all three bands. Replacing the coax stub proved to be the most challenging. I purchased some RG-6 U of unknown velocity factor but assumed to be around 0.80 based on what appeared to be foam dielectric. I shorted the existing stub at one end and attached my Autek RF-1 analyst at the other end and determined the impedance at 10 MHz, which seemed to be a reasonable standard for all measures. I really like the Autek RF-1. While it’s not as nice as the MFJ-259 or 269 at roughly $300 to $400, the price of $150 is a real bargain. Plus, the RF-1 does all that I need it to do and is compact for storage — where it spends most of its time.At 10 MHz the existing stub measured 142 ohms (L= 2.09 and C= 105). I then started trimming and measuring the RG-6 U cable until I came to the same readings. It measured 13 feet 3 inches, which computes to velocity factor of roughly 0.78. Installed, it works great.

I then set up the RF-1 at the antenna and proceeded to go through the tuning procedures. After first adjusting 80 meters, then 40 meters, and finally 30 meters. I went back and measured everything again. For 80 meters it covers 3.5 to 3.55 below 2.0 SWR, the CW portion where I spend my time. For 40 meters it covers 7.0 to 7.250 before rising to 2.0. And, of course, 30 meters covers the entire band at 1.0. In addition, the entire 15 meter band is covered at less than 2.0. This antenna works great, glad I spent the time sprucing it up. Should be good for another couple of years.