I recently built a quarter wave ground plane antenna, so that I could get back on the 4m (70MHz) band. I have made a page showing some images and construction details of this antenna which can be seen here.
Click the image to view construction details of the 70MHz quarter wave ground plane antenna.
I have been making a few 1/4 wave antennas lately, mainly for UHF and the GHz bands with good success, so I decided to create a calculator to simplify the process and maybe get some people who have not tried one before to give it a go.
For UHF for example, these can be made very cheaply, very easily and they perform well. Try one on 433MHz plugged into your handheld for example 🙂
The 1/4 wave ground plane
The calculator is at m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/
We went out for some portable operating today, as the weather was nice. Our club has a topband net each Saturday at 2pm and I wanted to try an antenna for the upcoming 160m AFS Club Calls contest. Using Dave M0TAZ’s 18m spiderbeam fibreglass pole as a loaded quarter wave, with an inductor (340μH) towards the top of the antenna. It makes it all a bit critical having the inductor so high, but the big advantage is that the bottom 15.5 metres has a lot of current in it, leaving only the 2.5 metres above it at a high impedance, making a better radiator. Ground was provided by a chicken wire fence, which I have used many times before with good results.
Below is a short video showing the antenna first on 24MHz where Dave is working Bahrain where the vertical was set up close to a ⅝ wave, then afterwards, it’s fully extended with the loading coil 15.5 metres up, making it a loaded ¼ wave for 160m. The antenna was resonant at 1830kHz, a bit low, so the ATU was used. I calculated for 1900kHz, so I guess 70kHz off isn’t bad! It would be easy enough to fine tune it. Lovely day for it, a bit breezy towards the end though!