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The FT-857 is designed use from (1) an external DC power source, (2) internal battery (requires optional FNB-78 Ni-MH
battery pack), or (3) AC power source (requires optional FP-30 Internal AC Power Supply).
External DC power source operation
The DC power connector for the FT-857 must only be connected to a DC source providing 13.8 Volts DC (±15%), and
capable of at least 22 Amperes of current. Always observe proper polarity when making DC connections:
The Red DC power lead connects to the Positive (+) DC terminal; and the Black DC power lead connects to the Negative
(–) DC terminal.
In mobile installations, noise pickup may be minimized by connecting the DC cable directly to your vehicle's battery,
rather than to the ignition switch or "accessory" circuitry. Direct connection to the battery also provides the best voltage
stability.
Tips for Successful Mobile Installations:
ρ Before connecting the DC cable to the battery, measure the voltage across the battery terminals with the engine
running fast enough to show a charge. If the voltage is above 15 Volts, the vehicle's voltage regulator should be
adjusted to reduce the charging voltage to 14 Volts or lower.
ρ Route the DC cable as far away from the ignition cables as possible.
ρ If the DC cable is not long enough, use #12 AWG (minimum) stranded, insulated wire to extend it. Be certain to
solder the connections at the splice securely, and provide ample insulation for the soldered splice (heat shrink tubing
plus black electrical tape work well).
ρ
Check the battery terminal connections frequently to be sure they are tight and not corroded.
ρ
When operating with the vehicle turned off, or operating from a stand-alone car battery (in a camp site, etc.), be
mindful of the minimum operating voltage (11.73 Volts) for the FT-857. If the battery is not charged sufficiently to
maintain at least 11¾ Volts at the radio, erratic operation or shut-down may occur.
Permanent damage can result if improper supply voltage, or reverse-polarity voltage, is applied to the FT-857. The
Limited Warranty on this transceiver does not cover damage caused by application of AC voltage, reversed polarity DC,
or DC voltage outside the specified range of 13.8V ±15%. Never attempt to connect the FT-857 to a 24-Volt battery
system.
When replacing fuses, be certain to use a fuse of the proper rating. The FT-857 requires a 25A fast-blow fuse.
Installation
Power Connections
Caution
5
FCC ID: K66FT-857
Operating Manual
Vertex Standard Co., Ltd.
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