Verticals Require Radials

(Fact or Myth?)

This discussion relates only to true 1/4 wave ground mounted monopole antennas usually referred to as "verticals". A vertical without radials is called a Marconi antenna.

Every few years several articles seem to appear in amateur radio publications which discuss the effects of radials on the performance of the 1/4 wave vertical. I have been looking at these articles for years and realized that the work required to embed several miles of wire in my lawn was not for me. Some of the articles show that the number of radials can be greatly reduced by elevating them a foot or so above the ground. This sounds good but how do I mow the lawn? The more radials the better they say, but the consensus seems to be that you can get by with between 16 and 40 radials.

Multi-band verticals seem to require a set of 1/4 wave radials for each band. This means that a vertical for all bands from 10M to 40M (leaving out 30M) would need over 1/4 mile of radial wire at 16 radials per band, and almost 3/4 mile at 40 radials per band. My back and knees hurt just thinking about it.

Because of the above, I have ignored the virtues of the vertical for my whole amateur radio life. What are these virtues you say? Well let's start with omni-directional radiation which means no dead spots in the pattern (there is an old joke that verticals radiate equally poorly in all directions). Then, there is the low take-off angle which means you will reach DX with fewer skips. The lower angle also results in less loss per skip. A vertical can be erected without supports like trees or towers. It can also be disguised as a flag pole for aesthetic or stealth reasons.

OK, so the vertical may be a good antenna, especially for DX, but what about those darned radials. Well how much do these radials actually improve the performance of a vertical? It turns out that 16 radials will gain you about 2db, and 40 radials will give only 1/2 db more than the 16 radials. So, is 2db worth the effort? How much is 2db in reality? An "S unit" is defined as 6db. The "S" meter on some receivers deviate from the definition, but 2db is basically 1/3 of an S unit. Is all that work laying down radials worth an improvement of 1/3 of an S unit? You can get the 2db back by increasing your power from 100Watts to 158watts.

Adding radials to a vertical can actually cause some problems. The impedance of a vertical without radials is not very frequency dependent. This means a very wide bandwidth. As radials are added, the bandwidth is reduced. Adding radials also lowers the impedance of the antenna to the point where a matching network or tuner is needed to achieve reasonable SWR's across a wide bandwidth.

For me, the choice is easy. A vertical without radials is simple to erect, and the 1/3 S unit loss is well worth the advantage of good SWR numbers across the entire band without the use of a tuner.