USER’S MANUAL
SERIES 48750 RF REPEATER
ANTENNA ISOLATION
ISOLATION BETWEEEN THE DONOR (BASE) ANTENNA AND SERVICE AREA ANTENNA
SHOULD BE 20 dB GREATER THAN THE GAIN OF THE REPEATER AMPLIFIER. If the isolation
is less than the amplifier gain, then positive feedback sufficient for oscillation is present in the system.
Such oscillations will overdrive one or both amplifier chains and continuously activate the AGC
auto-shutdown circuitry. This situation will be apparent by the Red Fault LED lighting up and then
quickly off every 2 seconds.
Antenna isolation is usally not a problem for in-building installations. Isolation is improved by using a
directive donor antenna and facing it away from the distribution or service antenna(s). Decoupling is
achieved by spatially separating the antennas vertically and/or horizontally. Other factors influencing
isolation include multi-path reflections, structures, other antennas, passing vehicles, personnel proximity,
etc. See applications engineering for assistance
It is always best to measure the isolation before connecting the repeater. The most direct way to measure
the isolation is to inject a known signal into one antenna, and measure the coupled signal at the other
antenna. This should be done across the applicable bandwidth to account for the frequency dependency
of standing waves.
DIAGNOSTICS / TROUBLESHOOTING
Green power LED not lit.
Check power source and the the AC fuse located in the EIC plug. Check for DC voltage. Is is rare that
the DC fuse will blow and most likely indicates a short of some kind in the repeater. The DC fuse is
accesable inside the unit. The Mini ATO 5 amp is a readily available fuse. It can be replaced, however, if
the fuse blows again, the unit should be return for service.
Green power LED lit and no Red Fault LED
If the green LED is on but the unit does not appear to be working, the mostly likely senario is a break in
the donor or distribution networks. First check both RF paths output via the DC voltages on Pins 12 and
13 or the RX DET.V and Tx DET. V from the PM700.
Also check to make sure that the donor signal is still available to the repeater, obstruction is blocking the
donor base site or the donor antenna has become misaligned. Then check the integrity of the distribution
network. Coaxial cable has a minimum bending radius, if that is exceeded the inner conductor may crack
or break causing excessive reflections to the signals.
Checking for DC Voltage
DC Voltage can be check via the 15 pin test port. Pins 10 and 11 are the DC voltage associated with the
AGC circuitry, there should be at least 7 volts to ground - pin 14. Or plug the PM700 monitor into the
test port and measure the RXAGCV to ground.
The Red LED indicates a summary fault from any of the fault conditions identified in the Test Points
section. Specific action is describe in that section.
TEST POINTS
T
T
h
h
e
e
D
D
-
-
s
s
u
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b
b
c
c
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.
T
T
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P
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0
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m
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4
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1
1
0
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.
.
T
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l
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w
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:
:
L
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,
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.
.
8Dwg 602300003500/Rev.1
8
