The best time to do this is early spring but it can be done other times, as well. I have even done it in the fall and had good success.
The idea behind this is to get the grass of your lawn to grow over the radials and protect them from the mower.
First, mow the grass pretty short in the areas where you will be laying the radials down. Notice, I didn't say "scalp" it. Just lower the mower until the grass is about 1 inch long after cutting. Readjust the height of the mower back to normal and put it away.
Next, connect the radials to the radial plate with wire terminal ends (which you can get at the store where you bought the radial wire) and stretch them out while arraying them evenly around the antenna. Some AM broadcast engineers tell us that the radials should be as long as you can make them up to about 1/2 wavelength. If you can only do 1/4 wave or 1/8 wave in certain directions then do that and don’t worry about it. You will be surprised how much better your vertical will work. After you install a few radials and see how much better you antenna performs you will have an urge to put in more of them. Don’t resist. More really is better.
OK – back to the installation.
Starting from the antenna end of the radials and about every 3-4 feet hold the wire down with a radial wire anchor pin while pulling the radial out from the antenna to keep it taut. Push it in as far as possible to get the wire as close to the grass roots as possible. I typically use a hammer to drive it home. If the radial wire is sticking up any place due to uneven ground or the wire is loose just put another staple there. The idea is to get all parts of the wire down as close as possible to the ground so that the grass can grow over it.
Here are some pix of what it should look like.
When you finish the last radial, your job is done. Mother Nature will do the rest. If you have done this in the early spring, the grass will grow up, surround the wire and pull it down firmly along its full length. If you do it in the fall after the grass has stopped growing, it will happen the next spring. This will be done so completely that in a few weeks you will have to actively look for the radials to see them.
Your mower will miss them completely, too; but you and your contacts will hear them right away!
73,
Paul
NO8D