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PAC 15-100C 450-470 MHz Amplifier PAC 15-100-C Instruction Manual

450-475 MHz UHF Commercial Amplifier
1
PAC 15-100-C
450 - 475 MHz UHF COMMERCIAL AMPLIFIER

This series of amplifiers is designed for 450 - 475 MHz band operation. The designs use
the latest in micro-stripline techniques and highest quality state-of-the-art transistors.
Relay switching is automatic RF sensing. These units do not require any tuning. The
broadband design offers the ultimate in flat input VSWR 1.4:1 or less, and produces rated
power output or better across the entire 25 MHz band.

BASIC OPERATION
The front panel switch puts the amplifier "in" or "out" of the transmission system. With
the switch "out" the RF supplied bypasses the amplifier. With the switch "in" the power
supply Voltage is applied to the RF sensing and relay circuitry inside the amplifier and
the green "ready" LED on the front panel lights up. No current is drawn, however, until
the transceiver or transmitter is keyed and RF is applied to the amplifier. Then an audible
"click" from the relay can be heard, the red "RF on" LED will light, and the RF supplied
will be amplified.

In over-temperature situations (circuit board temperature exceeds 160
°
F) the amplifier is
automatically switched "out" and the yellow "over temp" LED lights up. This can happen
when the amp is run harder than the ICAS rating and/or air circulation is inadequate.

Where a remote switch is desired, +13 VDC can be applied through a switch to the
"remote" phono jack on the rear panel. This provides remote "in-out" switching only
when the front panel switch is "out."

SPECIFICATIONS
POWER OUTPUT ............................ 100 Watts, nominal with 15 Watts of drive
POWER INPUT ................................ 5-15 Watts
FREQUENCY RANGE .................... 450-475 MHz, no tuning required
INPUT VSWR................................... Less than 1.5:1 from 450-475 MHz; less than 1.5:1
in the bypass mode
IMPEDANCE.................................... 50 Ohms, nominal
SUPPLY VOLTAGE ........................ 13.5 VDC, nominal (11-16 VDC)
SUPPLY CURRENT ........................ 20 amps, nominal
CONNECTORS ................................ RF jacks - Type "N"; Remote control - RCA
"phono"
PROTECTION CIRCUITRY............ Over-temperature sensor - 160
°
F (LED indicator
and automatic shutdown) Over current breaker
Reverse voltage - Shunt Diode PAC 15-100-C Instruction Manual

450-475 MHz UHF Commercial Amplifier
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OPERATING CLASS....................... AB1 Linear
KEYING............................................ COR keying provided automatically by applied
drive. Amplifier can be controlled remotely by
applying +14 Volts to the RCA jack center
conductor. This places the amp in "ready" mode.
TYPE ACCEPTANCE...................... This unit is type accepted under FCC part 90
SIZE................................................... 2.375" H x 7" W x 10" D

INSTALLATION
Installation of the PAC 15-100-C amplifier is quite simple. The output of the driving
transceiver is connected to the "XCVR" input via a short piece of coax (RG-8 preferred).
The output of the amplifier is connected to the vehicle's UHF antenna. It should be noted
that at this power level, RG-8 coax should be used for minimum losses and heating of the
coax. RG-58 is too small to avoid losses and dielectric heating should the antenna
develop VSWR problems.

The DC power to the amplifier should be provided from a source close to the battery
through at least #12 wire (with #10 preferred). At 18 amps of current, losses through
smaller wire and/or various pressure-type connectors may degrade power output
performance by generating voltage drops.

If remote switching is desired, another cable (preferably shielded) should be connected
between a positive 14 Volts through a switch to the remote input on the PAC 15-100-C.
The front panel switch must be "out" to use the remote jack.



No tune-up should be required as the circuit is broad-banded to cover the entire 450-475
MHz band. If tuning is required, refer to the factor for service. Only a qualified holder of
an FCC second-class radiotelephone license (or higher) should tune or otherwise adjust
this amplifier. Additionally, a spectrum analyzer should be used to monitor harmonic and
spurious outputs to ensure that proper operation is obtained.


PAC 15-100-C Instruction Manual

450-475 MHz UHF Commercial Amplifier
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CIRCUIT THEORY AND DESCRIPTION
The PAC 15-100-C uses modern solid state devices and stripline techniques to achieve a
broadband, high reliability power amplifier design.



The input signal from the driver transceiver is matched to the base of the PAC 15-100-C
driver transistor via a microstripline matching network. The collector of this stage is
impedance at this point where the signal is split for amplification by twin power amp
stages.

The base of each power amplifier stage is matched using stripline techniques and their
collectors are also matched to present the proper impedance for recombining at the
output.

Various small capacitors are used to tune out reactances of the lines and multi-section
matching networks to insure broad band tuning (450-475 MHz).

DC power is fed into the collector of each device via microstrip inductors and/or air
wound inductors.

DC ground returns are provided by either air-wound or microstrip inductors.

A low pass filter consisting of 1/4-wavelength sections of coax (at 2Fo) and a 1 turn coil
provides both a notch due to the characteristics of a 1/4-wavelength piece of coax, and a
low pass filter using the capacitance of the coax and the inductance of the coil.

A DPDT relay provides straight through (bypass) operation. It can be keyed using the
internal RF detector circuit. An MPSA-13 darlington transistor is used to key the DPDT
relay.




PAC 15-100-C Instruction Manual

450-475 MHz UHF Commercial Amplifier
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INSTALLATION HINTS
Should you have trouble with your PAC 15-100-C installation, check the following:

1) Are all cables low loss (RG-8 or better), 50 Ohm coax free from shorts or open
shielded?

2) Is your transceiver particularly sensitive to VSWR? Varying the length of coax
between the amplifier and transceiver or the amplifier and the antenna may reduce
interaction. An electrical 1/2-wavelength is generally the best choice (electrical 1/2-
wavelength = 1/2-wavelength x velocity factor).

3) Is the amplifier keying (RF) intermittently or "buzzing"? Check the output from the
driving transceiver to ensure that it has sufficient output. Check for high antenna
VSWR. Try changing coax length. Check for RF feedback into your transceiver due
to open mike cable shield, connecting cable shield, close antenna proximity, high
VSWR on feedline, etc.

4) Is the amplifier producing low output? Confirm proper drive level by checking with
a Wattmeter. Confirm proper supply voltage . . . 13.5 VDC at the amplifier. If it is
not 13.5 V, power will be down in direct proportion. If high VSWR is present on the
amplifier input but through (bypass) power is OK, one or more of the transistors may
be blown. They can be checked using an ohmmeter from base to collector and base
to emitter. Low resistance should be seen in one direction with high resistance in the
opposite direction (all DC ground and power supply connections must be removed to
check this, of course).


Do not overlook the possibility that the wattmeter may not be very accurate at this
frequency. Additionally, a wattmeter used at the lower end of its scale will not be as
accurate as when used at the upper end of the scale. (Accuracy is listed as a
percentage of full scale in most cases.)

TECHNICAL ASSISTANCE
If you have any problem with this unit first check the appropriate section of this manual.
If the manual does not reference your problem or your problem is not solved by reading
the manual you may call MIRAGE at 601-323-8287. You will be best helped if you have
your unit, manual and all information on your station handy so you can answer any
questions the technicians may ask.

You can also send questions by mail to MIRAGE, 921 HWY 25 South, Starkville, MS
39759 or by Fax to 601-323-6551. Send a complete description of your problem, an
explanation of exactly how you are using your unit, and a complete description of your
station. PAC 15-100-C Instruction Manual

450-475 MHz UHF Commercial Amplifier
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SCHEMATIC