By Bob Hill KG5WRY
After watching the video, “Lowest Cost Antenna Ground Spike You Will Find”, (featured in the January 2023 Chawed Rag), I decided to try this antenna build. I purchased a MFJ-1979 17 foot telescoping antenna from DX Engineering, a CB Radio Antenna Mirror Mount and a right-angle UHF adapter from Amazon, and a 12 inch nail from Home Depot. The radials for the antenna are made from four 40 foot sections of surplus communications wire I had on hand. Total cost: less than $100.
This turns out to be a very quick antenna build. The 12 inch nail bolts onto the CB mount. The telescoping antenna screws into the CB mount 3/8 thread. The right angle UHF adapter keeps the coax from being bent as the antenna is pushed into the ground. The radials are connected to the CB mount using a ring connector and a butterfly nut. The longest part of the build was measuring out the 40 foot radial wires and connecting them to a crimp ring terminal.
Tuning the antenna was also straight forward. Using a nanoVNA, I tuned the antenna for each band by extending the antenna to the calculated height (1/4 of wavelength) for a band, adjusting the height of the antenna for band resonance and marking that resonance point on the antenna with a permanent marker. By repeating this measurement I marked resonance points for 20, 17, 15, 12, and 10 meters. I have been pleasantly surprised that the resonance points of the antenna are repeatable by extending the antenna to the marked indications on the antenna. So to change bands, just extend the antenna to the marked height and it is ready to transmit on that band.
The SWR of each band is very good, with the worst SWR being under 2.0:1 for the 20 meter band. All other bands are close to 1.2:1 SWR.
The antenna is very portable with quick easy setup and teardown. The typical deployment is to connect the coax cable to the antenna, press the spike into the ground, raise the antenna to the desired band, unroll the 4 radials, and unroll the coax back to the radio site. The deployment time for the antenna is less than 5 minutes. Teardown of the antenna is almost as quick. I take care in rolling up the coax and radials so they will not kink on the next deployment.
The performance of the antenna is typical of a ¼ wave vertical. I can easily make coast to coast, North and South America contacts. With good conditions Europe and Japan are possible. As I was writing this article, I made two contacts to Moscow on 15 meters and got 5×7 quality/strength marks in the QSO.
This is now my primary portable antenna for the park.
MFJ 17 foot telescoping antenna: DX Engineering (Part Number: MFJ-1979)
CB Mirror Mount Amazon: https://www.amazon.com/dp/B07GDGVSQ7
12 inch Nail: Home Depot Model# 12HGSPKE Grip-Rite 3/8 in. x 12 in. Galvanized Spike Nail
Right Angle UHF Adapter: https://www.amazon.com/gp/product/B08Y5Z8YFY/ (be careful as some of these adapters from Amazon are crap. This version at least allows you to inspect the center conductor connection).