Table of Contents
Advertisement
FCC ID: K66FT-857
Operating Manual
Base Station Earth Grounding
Typically, the ground connection consists of one or more copper-clad steel rods, driven into the ground. If multiple
ground rods are used, they should be configured in a "V" configuration, and bonded together at the apex of the "V" which
is nearest the station location. Use a heavy, braided cable (such as the discarded shield from type RG-213 coaxial cable)
and strong cable clamps to secure the braided cables to the ground rods. Be sure to weatherproof the connections to ensure
many years of reliable service. Use the same type of heavy, braided cable for the connections to the station ground bus
(described below).
Do not use gas line pipes in an attempt to provide a ground connection! To do so creates a serious risk of
explosion!!
Inside the station, a common ground bus consisting of a copper pipe of at least 25 mm (1") diameter should be used. An
alternative station ground bus may consist of a wide copper plate (single-sided circuit board material is ideal) secured to
the bottom of the operating desk. Grounding connections from individual devices such as transceivers, power supplies,
and data communications devices should be made directly to the ground bus using a heavy, braided cable.
Do not make ground connections from one electrical device to another, and thence to the ground bus. This so-called
"Daisy Chain" grounding technique may nullify any attempt at effective radio frequency grounding. See the drawings
below for examples of proper and improper ground connections. If your coaxial cable does not connect directly to the
station ground bus, you may connect a ground cable to the Ground lug on the FT-857 rear panel.
Antenna Considerations
The antenna systems connected to your FT-857 transceiver are, of course, critically important in ensuring successful
communications. The FT-857 is designed for use with any antenna system providing a 50 Ω resistive impedance at the
desired operating frequency. While minor excursions from the 50 Ω specification are of no consequence, the power
amplifier's protection circuitry will begin to reduce the power output of there is more than a 50% divergence from the
specified impedance (less than 33 Ω or greater than 75 Ω, corresponding to a Standing Wave Ratio (SWR) of 1.5:1).
Two antenna jacks are provided on the rear panel of the FT-857. The "HF/50 MHz ANT" jack is used for HF and 50 MHz,
while the "144/430 MHz ANT" jack is used for 144 MHz and 430 MHz.
Guidelines for successful base and mobile station installations are shown below.
Mobile Antenna Installations
Mobile antennas for the HF bands, with the possible exception of those designed for 28 MHz, display very high "Q" due
to the fact that they must be physically shortened, then resonated using a loading coil. Additional system bandwidth may
be realized using the Yaesu FC-30 Automatic Antenna Tuner, which will present a 50 Ω impedance to your transceiver on
the 1.8 ~ 50 MHz bands so long as the SWR on the coaxial line connected to the FC-30 is below 3:1.
On the VHF and UHF bands, coaxial line losses increase so rapidly in the presence of SWR that we recommend that all
impedance matching to 50 Ω be performed at the antenna feedpoint.
Vertex Standard Co., Ltd.
7
Advertisement
Table of Contents
