User's Manual

Preparing for Installation
20 SkyZhone 45 Installation Guide
DR
A
FT
In addition to line-of-sight clearance, a well-engineered high-frequency path
will also incorporate additional clearance. Extra space is needed to
compensate for signal loss due to partial obstructions, atmospheric inducting,
and multipath reflections.
To maximize radio reception
• Calculate 0.6 times the first Fresnel zone
• Add this distance to the path clearance above the tallest obstacle in the
line-of-sight path.
A typical Fresnel zone clearance required at mid-path over a 10 mile link is 28
feet at 6 GHz. An on-line resource for Fresnel zone calculations is available
at:
http://home.infi.net/~allenk/freszone.html
Received Signal Level and link budget
The link budget is used to prevent signal reception problems. An Received
Signal Level (RSL) is calculated and compared to the receive threshold of the
SkyZhone 45SkyZhone 45 radio when the system is installed.
Use the following formula to calculate the RSL:
RSL (dBm) = Pout - FL1 + G1 + G2 - FL2 - Lp
where:
P
out
is the transmitter output power (in dBm). See Table 14 on page 46 for
values.
FL1 is the feeder loss of the transmit side (in dB). This is typically -1 dB.
G1 is the gain of the transmit antenna (in dB). Use the following values:
• +29 dB for the 2 foot antenna
• +33 dB for the 4 foot antenna
• +37 dB for the 6 foot antenna.
G2 is the gain of the receive antenna (in dB). Use the following values:
• +29 dB for the 2 foot antenna
• +33 dB for the 4 foot antenna
• +37 dB for the 6 foot antenna
FL2 is the feeder loss of the receive side (in dB). This is typically -1 dB.
Lp is the Path loss defined by:
Lp (dB) = 96.6 + 20 log10F + 20 log10D
where: F= 5.8 (frequency in GHz)
D=Distance of path in miles