About Electrical Grounding; About The Antenna; Antenna Consideration - Yaesu DR-1 Operating Manual

Setting up the Repeater

About electrical grounding

The DR-1 repeater, like any other communications apparatus, requires an effective ground system for maximum electrical safety and
best communications effectiveness. A good ground system can contribute to station efficiency in a number of ways:
• It can minimize the possibility of electrical shock to the operator.
• It can minimize RF currents flowing on the shield of the coaxial cable and the chassis of the repeater. Such currents may lead to
radiation, which can cause interference to home entertainment devices or laboratory test equipment.
• It can minimize the possibility of erratic repeater/accessory operation caused by RF feedback and/or improper current flow through
logic devices.

About the antenna

A good antenna installation is extremely important for transmission and reception purposes. Note the followings, as the type and
characteristics of the antenna largely determines whether the performance of the repeater can be fully realized.
• Use an antenna that is designed for the installation conditions and application objective.
• Use an antenna that is tuned for the operating band and frequency.
• Use an antenna and a co-axial cable with a characteristic impedance of 50Ω.
• Adjust the VSWR (standing wave ratio) until it is 1.5 or less for an antenna with an adjusted impedance of 50Ω.
• Keep the coaxial cable routing length as short as possible.
• Use lightening and voltage surge protection devises.

Antenna consideration

Repeater operation without a duplexer requires that two antennas be installed, one for receiving and one for transmitting, so that the
receiving antenna does not absorb energy from the transmitting antenna. There are a number of ways to do this, depending on the
TX/RX frequency separation, and on the locations available for antenna mounting. If a duplexer is used, a single antenna suffices for
both transmitting and receiving. If using a reduced-size duplexer, a six-cavity model (minimum) is recommended. Yaesu recommends
the use of the duplexer. For further details, contact your Yaesu dealer.
Regardless of the above choice, it is of paramount importance that the antenna(s) be mounted as high and in the clear as possible,
preferably within line-of-sight to all repeater users. Furthermore, losses in the feedline(s) must be minimized, so the feedline(s) should
be high quality, and as short as possible. If a long feedline is necessary, use coaxial "hardline" cable to reduce losses. Repeater
antennas should have an impedance of 50 Ω at the operating frequency. When separate receive and transmit antennas are used,
high-Q narrow-band types may serve to minimize interaction. However, when a single antenna is used with a duplexer, it should be a
low-Q wide-band type.
Cautions
z Never transmit without having a transmit antenna connected to the TX antenna jack of the Repeater.
z Create a loop (slack) in the coaxial cable directly underneath the antenna and fasten it so that the weight of the cable does not pull on the antenna or
connector itself.
z Install the antenna taking into consideration the securing supports and how the guying wires are positioned, so that the antenna does not fall over or get
blown away in strong winds.
12
To prevent damage from lightning,
atmospheric electricity, electrical shock,
etc., provide a good earth ground.
Use a short, thick, braided
cable to connect your
station equipment to
the buried ground rod
(or alternative earth
ground system).