Specifications

13FT-857D Operating Manual
door to the rest of the vehicle’s body, using a heavy braid bonded securely at both ends, to
ensure that as much counterpoise as possible is secured. In portable operation, be sure to
lay out radials (or otherwise construct a n image plane for the vertical monopole); it is not
adequate simply to connect a vertical radiating element to the rear panel Antenna jack of
this transceiver, without providing a suitable counterpoise.
Base Station Antenna Installations
When installing a “balanced” antenna such as a Yagi or dipole, remember that the FT-857D
is designed for use with an (unbalanced) coaxial feedline. Always use a balun or other
balancing device so as to ensure proper antenna system performance.
Use high-quality 50 Ω coaxial cable for the lead-in to your FT-857D transceiver. All efforts
at providing an efficient antenna system will be wasted if poor quality, lossy coaxial cable
is used. Losses in coaxial lines increase as the frequency increases, so a coaxial line with
0.5 dB of loss at 7 MHz may have 6 dB of loss at 432 MHz (thereby consuming 75% of
your transceiver’s power output!). As a general rule, smaller-diameter coaxial cables tend
to have higher losses than larger-diameter cables, although the precise differences depend
on the cable construction, materials, and the quality of the connectors used with the cable.
See the cable 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 Cables
INSTALLATION
ANTENNA CONSIDERATIONS
CABLE TYPE
RG-58A
RG-58 Foam
RG-8X
RG-8A, RG-213
RG-8 Foam
Belden 9913
7/8” “Hardline”
1.8 MHZ
0.55
0.54
0.39
0.27
0.22
0.18
< 0.1
LOSS
28 MHZ
2.60
2.00
1.85
1.25
0.88
0.69
0.25
432 MHZ
>10
8.0
7.0
5.9
3.7
2.9
1.3
Loss 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
in the event of a catastrophic support or power-pole structural failure. Ground your anten-
nas’ 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,
if rotary 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.