Instruction manual

The one shown is 9 turns, 1 inch inside diameter, and wound with #14 enameled wire. The coil needs to be about 1

uH, plus or minus, depending on the input impedance of the antenna, The inductance of the coil is changed by

adjusting the spacing between the turns. Properly adjusted, the SWR will be less than 1.6:1 over the antenna’s

operating range (typically, 80 through 10 meters).

The coil will have the greatest effect on 80 and 40 meters, so those bands should be used to adjust the coil’s

spacing. Although the procedure can be done with an SWR bridge, it is much easier to accomplish with an antenna

analyzer, like the MFJ 259B.

Once the best SWR is found for 80 meters, check the SWR on 40 meters. It may be necessary to compromise

between the two settings. Once a good compromise is found, check the SWR on 20 meters. It should be equal to,

or slightly below the previous measurements.

If the lowest obtainable SWR is in excess of 1.7:1, it is an indication that the image plane losses are high, and/or

there is excessive coupling of the antenna to the body of the vehicle. If the SWR is below 1.7:1 without any

matching, it is a sure sign your installation needs to be improved.

The key to efficient operation is to have the best possible image plane under the antenna. In other words, it is the

mass under the antenna, not along side, that counts. Mounting antennas atop long posts, trailer hitch extensions, or

other mounting schemes where the body of the vehicle is far removed from the base of the antenna, will yield less

than stellar results.