Yaesu FT-7900R Operating Manual

Also see for FT-7900R: Technical supplement

6 FT-7900R O PERATING MANUALANTENNA CONSIDERATIONSThe FT-7900R is designed for use with antennas presenting an impedance of near 50 Ohmsat all operating frequencies. The antenna (or a 50 Ohm dummy load) should be connectedwhenever the transceiver is turned on, to avoid damage that could otherwise result if trans-mission occurs accidentally without an antenna.Ensure that your antenna is designed to handle 50 Watts of transmitter power. Some mag-netic-mount mobile antennas, designed for use with hand-held transceivers, may not becapable of withstanding this power level. Consult the antenna manufacturer’s specificationsheet for details.Most all FM work is performed using vertical polarization. When installing a directionalantenna such as a Yagi or Cubical Quad, be certain to orient it so as to produce verticalpolarization, unless you are engaged in a special operating situation where horizontal polar-ization is used. In the case of a Yagi antenna, orient the elements vertically for verticalpolarization; for a Cubical Quad, the feedpoint should be at the center of one of the verticalsides of the driven element (or at a side corner, in the case of a diamond-shaped CubicalQuad).Note that this transceiver is designed with wide frequency coverage in the VHF/UHF spec-trum. For general listening, you may wish to have a broadband antenna such as a disconeavailable, as a directional antenna such as a Yagi will have degraded performance outsidethe Amateur band for which it is designed.Excellent reference texts and computer software are available for the design and optimiza-tion of VHF and UHF antennas. Your dealer should be able to assist you with all aspects ofyour antenna installation requirements.Use high-quality 50 Ohm coaxial cable for the lead-in to your FT-7900R transceiver. Allefforts at providing an efficient antenna system will be wasted if poor quality, lossy coaxialcable is used. Losses in coaxial lines increase as the frequency increases, so an 8-meter-long(25’) coaxial line with under 1 dB of loss at 144 MHz may have a loss of 3 dB or more at 446MHz; choose your coaxial cable carefully based on the installation location (mobile vs.base) and the overall length of the cable required (for very short runs of cable in a mobileinstallation, the smaller, more flexible cable types may be acceptable).INSTALLATION