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VEHICLE-MOUNTED ANTENNAS

Because many amateur operators use mobile and portable transmitting units, an effort was made to obtain representative field measurements near some of these sources. Measurements were made inside and outside of vehicles on which various antennas were mounted. These measurements were made in cooperation with the licensee of Station D, both near his residence and in an open field.

(1) 2 m Band Whip Antenna

The first series of measurements was made relative to a 48 centimeter (cm) quarter-wave, vertical, whip antenna mounted on a small compact car. The antenna was mounted at the center of the rear of the roof just above the hatchback. It was operated with about 85 watts of transmitter output power at a frequency of 146 MHz. Measurements were made in the driver's position, in front and rear passenger locations, and around the outside of the vehicle. The measurements were made while the car was parked on the concrete driveway of a private residence. A van was parked directly beside the car during one set of measurements. Results of the measurements are given in Table 28.

(2) Open Field Test (Yagi and Quagi Antennas)

The second series of vehicle measurements was designed to determine typical field strength readings in an "open-field" environment, such as might be encountered as part of an outdoor amateur radio event. For these measurements two antennas were mounted on a single, rotatable pole attached to the roof of a van. The van was positioned in the middle of a large, open field with a dirt surface.

The antennas used were a five-element Yagi transmitting at approximately 50 MHz and an eight-element "Quagi" transmitting at about 144 MHz. The height of the Yagi antenna was approximately 4 m above ground, and the Quaqi antenna was mounted approximately 1.5 m directly above the Yagi antenna. Measurements were made using various powers and with respect to various orientations of the antennas. Results of the measurements for these two vehicle-mounted antennas are given in Table 29.

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