Ground-mounted 1/4 wave verticals
- How many / how long my radials should be ? -
Small city lots perspective
Context I succeeded in putting up a vertical antenna for 160 and/or 80m and/or 40m. Now, I know I need to put radials, but I can't install 120 radials, 1/2 wavelength long, in a complete 360° circle. So how many, and how long should they be? What about the antenna performances ? Things are easier than what they can look like ! |
My reference readings
A lot of competent guys have made and published extensive studies on this topic. This page is voluntarily simplifying this subject. For those who want to learn more, here are some more than interesting documentation :
Rules of thumbs
1. The more radials, the better. 2. The longer, the better. |
==> Prefer 16 radials of 10m long instead of 4 radials of 40m each, even for 160m ! |
Few figures as guidelines
It is obvious that 4x 6m long radials will not only provide excessive losses, but also decrease over-all performances (efficiency, mismatching).
==> A minimum of 8 radials is strongly recommended for any ground-mounted 1/4 wave vertical.
==> A minimum of 8 radials is strongly recommended for any ground-mounted 1/4 wave vertical.
Practical example
My set-up = 48 radials of 10m each for my 160/80/40/30m antenna with unique ground plane. From the above table, this gives me - Good results on 40m (1.1 dB loss due to ground plane, 1/4 = 0.25 wavelength radials) - Average results on 80m (1.9 dB loss due to ground plane, 1/8 = 0.125 wavelength radials) - Poor results on 160m (2.2 dB loss due to ground plane, 1/16 = 0.06 wavelength radials) |
Do what you can ! |
Conclusion
Apply the "Do What You Can" method : Put as many radials as possible, as long as possible and in as many directions as possible !!!!!!
You can even place radials of different lengths depending on your property "shape" and size.
In general within small city lots, you will not ask yourself "are my radials too long for their number". It is very unlikely that you'll waste copper wire !!!!
And at the opposite, adding "longer than recommended" radials can not hurt.ny
You can even place radials of different lengths depending on your property "shape" and size.
In general within small city lots, you will not ask yourself "are my radials too long for their number". It is very unlikely that you'll waste copper wire !!!!
And at the opposite, adding "longer than recommended" radials can not hurt.ny