Yaesu FT-857 Operation Manual

Also see for FT-857 series: Manual Technical supplement Brochure & specs Operating manual Technical supplement

Contents

Yaesu FT-857 Operation Manual Manual pdf 15 page image

13FT-857 Operating Manualrest of the vehicle’s body, using a heavy braid bonded securely at both ends, to ensure that asmuch counterpoise as possible is secured. In portable operation, be sure to lay out radials (orotherwise construct a n image plane for the vertical monopole); it is not adequate simply toconnect a vertical radiating element to the rear panel Antenna jack of this transceiver, with-out providing a suitable counterpoise.Base Station Antenna InstallationsWhen installing a “balanced” antenna such as a Yagi or dipole, remember that the FT-857 isdesigned for use with an (unbalanced) coaxial feedline. Always use a balun or other balanc-ing device so as to ensure proper antenna system performance.Use high-quality 50 W coaxial cable for the lead-in to your FT-857 transceiver. All efforts atproviding an efficient antenna system will be wasted if poor quality, lossy coaxial cable isused. Losses in coaxial lines increase as the frequency increases, so a coaxial line with 0.5dB of loss at 7 MHz may have 6 dB of loss at 432 MHz (thereby consuming 75% of yourtransceiver’s power output!). As a general rule, smaller-diameter coaxial cables tend to havehigher losses than larger-diameter cables, although the precise differences depend on thecable construction, materials, and the quality of the connectors used with the cable. See thecable manufacturer’s specifications for details.For reference, the chart below shows approximate loss figures for typically- available co-axial cables frequently used in HF installations.Loss in dB per 30 m (100 feet) for Selected 50-ohm Coaxial CablesINSTALLATIONANTENNA CONSIDERATIONSCABLE TYPERG-58ARG-58 FoamRG-8XRG-8A, RG-213RG-8 FoamBelden 99137/8” “Hardline”1.8 MHZ0.550.540.390.270.220.18< 0.1LOSS28 MHZ2.602.001.851.250.880.690.25432 MHZ>108.07.05.93.72.91.3Loss figures are approximate; consult cable manufacturer’s cata-logs for complete specifications.Always locate antennas such that they can never come in contact with outdoor power lines inthe event of a catastrophic support or power-pole structural failure. Ground your antennas’support structure(s) adequately, so as to dissipate energy absorbed during a lightning strike.Install appropriate lightning arrestors in the antenna coaxial cables (and rotator cables, ifrotary antennas are used).In the event of an approaching electrical storm, disconnect all antenna lead-in, rotator cables,and power cables completely from your station if the storm is not immediately in your area.