FM Dipole Antenna for 88-108 MHz
Model: PAFM-VDP-AL - Aluminum FM Dipole Antenna
The PAFM-VDP-AL antenna is a vertically polarized, offset dipole antenna covering the 88-108 MHz spectrum. The antenna is composed of high strength 6061-T6 structural aluminum and is mounted to a mast of 3" max OD (mast not included). The radiating elements are removable to reduce volume for shipping ease.
The antenna on it's own or in an array can be tuned for a VSWR of less than 1.10:1 for 4 MHz of band width or less than 1.25:1 across the entire band from 88-108 MHz.
Gain of the antenna system can be increased by adding additional PAFM-VDP-AL's and mounting them vertically one on top of another, each layer being call a "bay". A stack of 4 PAFM-VDP-AL's, for example, is a 4 bay array.
An exposed dipole in free space has unity gain, or 0 dBd gain. However, exposed dipoles also react with adjacent metal objects, the degree of which depends on the proximity and size of the adjacent metal objects. When a vertically polarized exposed dipole is mounted to a rear vertical metallic mast, the mast provides some signal reflection resulting in modest gain and directivity.
Tuning of the PAFM-VDP-AL for optimum VSWR takes into consideration the presence and impedance effect of a rear mounting mast as the primary support structure. Once mounted to a rear metallic support mast, a single PAFM-VDP-AL provides a gain of 2.0 dBd.