Tuning The Duplexer And Repeater Operational Tests; Overview; Programming The Radios; Tuning The Receive Radio Section - Motorola CDR500 Programming Manual

Overview

Before using your repeater, you must tune the
duplexer, using one of the following three methods for
ensuring that the duplexer is tuned to the correct fre-
quencies of operation:
• Pre-Tuned Method (preferred method)
Order the duplexer from the manufacturer or
supplier pre-tuned to the desired frequencies.
This is not a "method" of tuning the duplexer
but does not require any test equipment.
• Visual Method
Use a tracking (sweep) generator and spectrum
analyzer to adjust the tuning of the passbands
and reject bands of the duplexer.
• "In a Pinch" Method
The following paragraphs address a simple
method of tuning a "notch" (reject) duplexer
such as the TDN7407 UHF duplexer. This is not
as accurate a method of tuning as the visual
method afforded by the tracking generator/
spectrum analyzer sweep setup but it is much
less costly. It may be sufficiently good for all but
the most exacting applications. Use this method
only when the operating frequencies of the
receiver and transmitter satisfy the require-
ments of the duplexer. For example, the
TDN7407 is designed for a transmitter/receiver
frequency spacing of 5 MHz. If the operating
frequencies for the repeater are appreciably dif-
ferent than that 5 MHz specification, degraded
performance of the repeater will result.
The following procedure assumes that the CDR500 or
CDR700 repeater is fully assembled and the radios and
duplexer are mounted in the housing. The radios
should be connected to the proper ports of the
duplexer with the RF coaxial cables provided in the
HKKN4002 optional internal duplexer cable. The front
panel of the CDR700 must be removed to gain access to
the tuning screws of the duplexer.
March, 2001
Tuning the Duplexer and
Repeater Operational Tests

Programming the Radios

1. Program the receive radio with an additional
"receive only" mode at the frequency of the
transmit radio.
2. Program the transmit radio with an additional
"receive only" mode at the frequency of the
receive radio.
Instead of programming additional
modes, you can connect the coaxial
cables from the radios to the "opposite"
ports of the duplexer.
3. Connect a Communications System Analyzer
(CSA), such as the Motorola R2000 series, or
an RF signal generator to the antenna port of
the duplexer. The CSA should be operating in
the "Generate" mode. Modulate the RF source
with a 1 kHz tone at 60% system deviation to
facilitate "hearing" the signal during the tune-
up procedure.
Before proceeding, ensure that the
repeater is disabled.

Tuning the Receive Radio Section

Tuning the receive radio section of the
duplexer begins with the tuning screw
closest to the antenna port of the
duplexer.
1. Adjust the frequency of the CSA or generator
to that of the transmit radio.
2. Place the receive radio on the transmit radio
frequency mode defined in Step 1 under "Pro-
gramming the Radios."
3. Adjust the level of the CSA or generator until
a weak signal is heard from the receive radio.
4. Increase the level of the CSA or the generator
by approximately 20 dB.
5. Adjust the tuning screw of the duplexer for
the greatest rejection of the signal. This will
appear as a noisier signal. If necessary:
6864110R66-O
Section 5
NOTE
NOTE
NOTE
5-1