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RF-7000E Operations Manual
Chapter 3. Mounting the Antennas
— 45
Antenna Feedlines
The RF-7000E repeater uses waveguide feedlines. For the 7.1 ~ 7.9 GHz band, typical feedlines are
elliptical waveguide such as EWP77 and EP78. The RF-7000E has CPR112G Waveguide Flanges at
the top antenna ports. The equipment end of the waveguide feedline must have a matching
CPR112G flange installed. Two half height gaskets are used when a pressure window is installed.
The antenna end of the waveguide feedline must have a connector flange that matches the installed
antenna’s flange. Typical antenna flanges in this band are CPR112G and PDR84.
Waveguide feedlines require dehydration equipment to maintain a dry atmosphere within the
waveguide to prevent moisture accumulation which leads to corrosion and higher transmission
losses. RF repeater applications typically have shorter waveguide runs and thus, a smaller volume of
air within the waveguide. Static desiccators are ideal in this situation. A static desiccator will passively
dry air passed through its silica gel as daily temperature and pressure changes gently move the air.
These units do not require any power to operate and provide 1 to 2 years field lifetime before
requiring replacement or service. Peninsula Engineering recommends mounting static desiccators
inside the repeater enclosure to protect against aging from direct sunlight. See manufacturer’s
specifications and recommendations when considering static desiccators.
Dry Nitrogen is another method to keep waveguides dry without using power. Nitrogen supplied in
high pressure bottles is reduced in pressure with a regulator and then passed to a gas pressurization
manifold with distribution to the feedlines. Nitrogen replaces the air within the waveguide (purged at
installation) and the positive pressure helps force moisture away from entering the waveguide. To
warn of an empty gas bottle, the optional RMAS alarm equipment can be optionally provisioned with
a low pressure switch that can be added to the pressurization manifold. When gas pressure drops
below 1 psi, a warning alarm is issued.
RF-7000E repeater configurations require one feedline per equipment antenna port, typically:
One for the primary West antenna
One for the primary East antenna
One for the diversity West antenna, if applicable
One for the diversity East antenna, if applicable
One per direction and polarization in Y-Junction applications
The allowable transmission loss for antenna feedlines is specified in the site plan or path calculation,
path data sheet documentation for the project. Do
not
install feedlines different than as specified.
Feedline Installation
To install waveguide feedlines:
1.
Install the top connector (goes to the antenna). Use a flaring tool for best attachment and
impedance, Z
0
, match.
2.
Raise the waveguide up the tower to the antenna. Use a hoisting grip.
3.
Position the waveguide and secure the top section. Carefully bend the elliptical waveguide to
align with the antenna flange. Be mindful of the bend and twist specified limits of the waveguide.
If necessary, use rigid twist and bend sections to aid in alignment.
4.
Connect the waveguide to the antenna.
5.
Securely install the feedline so that it reaches to the installation site of the RF-7000E, with
enough room to connect to the repeater.
6.
Secure the cable to the tower or structure about every 3 feet or 0.9 meters.
7.
Carefully measure and cut to length the waveguide.