Sentinel & PimaGuard
Installation Guide 27
A
PPENDIX
A R
ECOMMENDED
T
RANSCEIVER
S
PECIFICATIONS
The following table contains a list of recommended specifications for connecting a narrowband VHF or UHF transceiver to
the PimaGuard:
A
PPENDIX
B C
ENTRAL
S
TATION
I
NSTALLATION
C
HECKLIST
Radio Transceiver
The transceiver should follow these guidelines:
1. It should be a narrowband receiver (12.5 KHz);
2. No data transmission (e.g. ID, pre-transmission message) is allowed within the transmission;
3. The squelch should always be turned OFF (i.e., signal and noise are fully transferred into the Sentinel).
It can be set either manually or internally:
a.
Manual adjustment squelch: turning the receiver OFF and ON does not change the squelch state;
b. Internal squelch: the squelch is turned OFF by the manufacturer or supplier of the Radio Transceiver.
4. The receiver signal output level should be constant and not to be effected by the volume control knob or
the received signal strength (i.e., any Automatic Gain Control (AGC) must be turned OFF);
5. When a repeater is in use, the transceiver shouldl always transmit (i.e., unconditionally).
6. The transmitter wakeup time (i.e., how long it takes from the time the PTT is pushed until it starts
transmitting) should be less than 150 mSec.
Antenna & Cable
1. The antenna should have at least a 4.7 dB attenuation;
2. For a length of less than 20 meters between the antenna base and the radio transceiver, an RG-213
antenna cable should be used. For a length of more than 20 meters a Helix antenna cable should be used;
3. All antenna connections should be sealed against wetness.
4. The antenna cable should not run in parallel to any electric wires to avoid RF interferences. If this is
unavoidable, the cable should run at least 1 meter away from the electric wires.
5. When the transceiver is in use, the Voltage Standing Wave Ratio (VSWR) should be 1.5V max (i.e., the
returning waves are less than 4%).
Feature
Transceiver
Squelch
• Squelch switch should be manually adjustable;
• Squelch switch status should be retained after transceiver powered off;
• Internal Squelch switch should also be turned off;
Output Signal
• Speaker switch (optional);
• Maximum output signal (ext. speaker) should not exceed 1Vp-p;
• Output signal should remain constant at all time, i.e., is not volume and/or speaker
switch dependent;
• Output signal should not include data like start-up ID, pre-transmission message, etc. (this
is usually a settable feature)
I/O Interface
• Wires length should support up to 1 meter;
• PTT Control;
• GND;
• Audio IN (MIC input can be used instead);
• Audio OUT (constant output signal);
Power source
• The technical specifications of the power source should comply with the transceiver’s
manufacturer specs. On top of that, it is important that the power source will be clean
from ripple noise.
Antenna
• It is advisable to install the antenna on as high as possible location (e.g., communication
antennas tower).
• The antenna cable should be a Heliax, RG203, or RG19 cable. These cables are
mechanically strong and minimize any signal attenuation.
• A 5.25 dB antenna is usually sufficient for radio transmissions.
Some transmitters interrogate the network when the PTT is pressed and will not
transmit if it is busy (i.e., when a signal is received by the receiver).
The antenna should be connected directly to the ground to minimize any
damage caused by a direct hit from a lightning.
