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.
Tag: quarter wave
1/4 Wave Antenna Calculator
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 calculator is at m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/
Loaded Quarter Wave Antenna on Topband
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!