Mirage B-215-G User manual

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Table of Contents
MIRAGE B-215-G RF Amplifier...................................................................................................1
Specifications ..................................................................................................................1
Installation.......................................................................................................................2
Front Panel Switches/LED's............................................................................................2
Rear Panel Connectors:..................................................................................................3
Internal Adjustments: ......................................................................................................3
B-215-G Tuning Procedure.............................................................................................3
Setting the Idling Current....................................................................................3
Measurement of Insertion Loss..........................................................................4
Tuning the Amplifier ...........................................................................................4
Setting the Trip Points........................................................................................5
Adjusting The Receive Preamp..........................................................................6
Troubleshooting:..............................................................................................................7
Technical Assistance ......................................................................................................7

MIRAGE B-215-G
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MIRAGE B-215-G RF Amplifier
The Mirage B-215-G is an RF power amplifier for 144 - 148 MHz. Features include automatic
power shut-down circuitry for protection against high antenna VSWR, high temperature and
excessive RF power input. A GaAsFET receive pre-amp provides high gain and low-noise
amplification for weak signal applications. The pre-amp includes an attenuator to reduce signal
output level. This is useful in preventing receiver overload and subsequent intermodulation
distortion caused by strong signals. Provision is made for automatic or remote (external) keying,
and for remote control of all front panel functions using the Mirage RC-1 Remote Control Unit.
The Mirage B-215-G is capable of FM, SSB, and CW operational modes.
Specifications
Frequency range: 144 to 148 MHz
RF input power (Drive): 250 milliwatts to 5 Watts
RF output power: 150 Watts (maximum) with 2 Watts drive
Duty cycle: Intermittent (ICAS)
Modes: FM, SSB, CW
Receive pre-amp: GaAsFET, Gain 21/15 dB-Nominal. Noise figure
less than 0.6 dB. 1 dB compression point greater
than -13 dBm input (Nominal)
VSWR power shut-down point: 3:1 approximately
RF input power shut-down point: 5 Watts Nominal
Temperature power shut-down point: 175 Degrees F.
Keying: Automatic (RF sensing) or remote (external)
Input/Output impedance: 50 Ohms
RF connectors: SO-239 (UHF)
Remote keying connector: RCA phono
Remote control connector: 6 pin Molex
Supply voltage: 13.8 Vdc (for full RF power output)
Supply current: 25 Amps (Nominal)
Fuse: Low voltage, fast-blow, 35 Amps
Physical dimensions: 12" x 3" x 5 1/2"
Weight: 5 Lb.

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Installation
The Mirage B-215-G may be mounted using the brackets supplied or simply placed in a
convenient operating position. In either case, there must be adequate ventilation for the finned
heat sink. This generally means at least 1 inch clearance from the sink to any surrounding
enclosure and an unobstructed flow from the front to the back of the sink.
+CAUTION:With extended use, the heat sink becomes very hot!
If it is necessary to extend the DC power leads, use a minimum #8 gauge insulated wire. Use a
minimum length of good quality 50 Ohm coaxial cable between the radio and the amplifier. For
the best performance, the antenna system should have a VSWR of 1.5:1 or better. The receive
pre-amp gain is set to the HIGH value at the factory. To switch to minimum gain, move the DIP
switch located under the left side cover near the power supply leads to the UP position. The
switch may be accessed through the fourth slot from the rear using an appropriate small tool. If
desired, the transmit relay hold-in (hang-time) may be adjusted by adjusting the potentiometer
located behind the twelfth slot from the rear on the right side of the amplifier.
Block Diagram
Figure 1
Front Panel Switches/LED's
Power ON/OFF switch: Turns the DC power ON or OFF.
SSB/FM switch: Selects relay time delay for the mode of operation. The relay drop
time is lengthened for the SSB mode of operation.
Pre-amp ON/OFF switch: Turns pre-amp power ON or OFF.
Power LED: Indicates that DC power is applied.
Pre-amp LED: Indicates that the pre-amp is turned on.
TX LED: Indicates that the amplifier is keyed ON.
SWR/Overload LED: Indicates amplifier shut-down due to excessive VSWR,
temperature, or RF drive power.

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Rear Panel Connectors:
RADIO (SO-239): RF input from radio.
ANT (SO-239): RF output to antenna
RCA phono (unmarked): Remote keying
MOLEX (unmarked): Remote control
Internal Adjustments:
SSB Delay: This allows the RF relay hang-time or delay to be adjusted to
the time desired.
Pre-Amp attenuator switch: Sets the pre-amp gain to full or reduced value.
Input VSWR and output power: These adjustments are made at the factory and should not
require field adjustment.
Pre-amp tuning: These adjustments are made at the factory and should not
require field adjustment.
B-215-G Tuning Procedure
The information contained below is for general information only. You are not required to perform
these alignment procedures to make the amplifier operational as they have already been
completed at the factory.
Setting the Idling Current
1. Connect the amplifier to the dummy load before making any other connections to prevent
damage.
2. Lift one end of the input voltage protection fuse from its socket.
3. Ensure that your DC voltage from the power supply is OFF.
4. Connect the power supply and all other connections to the amplifier. Ensure that the exciter
radio is OFF until directed.
5. Place a SHORTED RCA plug into the RCA jack located on the rear of the amplifier. This will
cause the transmit relay to energize when the amplifier power is switched ON.
6. Using the lifted end of the protection fuse and the unused side of the fuse socket, insert a
meter capable of reading current from 0 milliamps to 5 amps.
7. Apply power to the amplifier and turn the unit ON while observing the current reading on the
meter.
+CAUTION:If current surges too high, immediately remove power!

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8. Upon application of power, the initial reading should be approximately .64 amps of current.
9. Locate the driver bias pot, R37, and raise the current 60 to 80 milliamps for a reading of
approximately .70 to .72 amps on the meter.
10. Locate and adjust the power amplifier bias pot, R42, to reflect an additional 20 milliamps on
the meter for a reading of approximately .90 to .92 amps.
11. Turn the unit OFF and remove the DC power.
12. Remove the shorted RCA plug from the RCA jack on the amplifier.
13. Disconnect the meter from the circuit and place the fuse back in the holder.
Measurement of Insertion Loss
1. Ensure that the power is in the OFF position on the front panel.
2. Set the frequency of the exciter radio to the center of the allocated band (In the case of the
Amateur band, 146.000 MHz).
3. Turn the exciter radio ON and adjust the output power to 1 watts FM or CW when keyed.
4. Verify that there is no reflected power.
5. Increase the power to 2 watts and measure the insertion loss through the relay contacts.
6. With 2 watts injected, the output watt meter should read 1.6 watts or more. The difference is
the insertion loss, which should be no more than .4 watts. The input reflected should read
less than 40 milliwatts.
Tuning the Amplifier
−NOTE: Key-up by applying RF during test only. While tuning & testing, always observe
current draw, spectrum analyzer and input VSWR.
1. Key the exciter radio and adjust the output power to 1 watt FM or CW.
2. Turn the DC power supply ON.
3. Place the front panel power switch in the ON position.
4. Quickly, and with minimum key up time, adjust the C65 trimmer capacitor on the output side
of the final power transistors for the maximum power output as shown on the output power
meter and minimum current draw.
5. Simultaneously observe the input reflected power meter and adjust C65 for the minimum
VSWR on the input while maintaining the maximum power that can be obtained on the output.

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6. Observe the spectrum analyzer and readjust C65 if any spurs or oscillations are present.
7. Adjust capacitor C39, located on the input side of the driver transistor, Q8, for minimum
reflected power on the input meter and maximum output power.
8. Again, observe the spectrum analyzer and readjust if any spurs or oscillations are present.
Unkey the transmitter.
9. Place the power switch on the front panel in the OFF position.
10. Increase the drive signal on the exciter radio to 1.5 watts.
11. Place the power switch on the front panel in the ON position.
12. Repeat steps 4 through 8 above.
13. Place the power switch on the front panel in the OFF position.
14. Increase the drive signal on the exciter radio to 2 watts.
15. Place the power switch on the front panel in the ON position.
16. Repeat steps 4 through 8 above.
17. Check the power out and input reflected for tolerances at 144, 146, and 148 MHz. The power
should read at least 150 Watts. Current at full power output should not exceed 24 amps at
13.8 Vdc.
Setting the Trip Points
1. The next step is to set the Overdrive trip point at 5 to 7 watts. This is accomplished by the
selection of the proper trip diode ZD2 which is normally a IN755. If circuit trips too soon, a 2pf
capacitor (C3) may be placed at junction of R1-C1 from strip line to ground of circuit board.
Or, you may substitute a short piece of 50 ohm mini coax for C3. It may be soldered to strip
line. Solder the center conductor to strip line at the R1 - C1 junction. The shield should be
soldered to ground. Trim coax to proper length to set trip point at 5 to 7 watts drive. Check
trip at both ends of band, 144 MHz, 148 MHz. Set trip at 5 watts at most sensitive end of
band.
2. Set the drive level to a level that will give 150 watts indicated on the output watt meter. Unkey
the transmitter. Remove the coax marked antenna on the amplifier (output coax).
Momentarily key up or apply drive signal to amplifier. Amplifier should go immediately into
VSWR fault. DO NOT HOLD THIS KEY CLOSED FOR MORE THAN 3 TO 4 SECONDS, as
the output of amplifier is open with no load on it. If amplifier does not go into fault, the SCR
circuit is defective. If amplifier does go into fault, proceed to next step. Be sure to check at
the upper and lower limit of the band.

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3. Next place a 3:1 mismatch dummy load at the output of the amplifier. The shut-down trip
point must be set to the most sensitive end of the band. The trip may be adjusted so the
circuit just trips at 140 to 152 watts. Adjust the trip by selecting proper diode as shown on
print as ZD3, and/or select the proper capacitance C25 across R24, the 62 ohm resistor
shown on the pick-up trace. A piece of 50 ohm coax, approximately 2 inches long, may be
substituted for C25 and cut to proper length to adjust the trip point. Remove the 3:1 dummy
load and reconnect the output coax.
−NOTE: C25 may be removed or temporarily disconnected to make the shutdown circuit
more sensitive.
4. Set SSB - FM switch to SSB. Key up and set SSB relay pot for 2 to 3 seconds of hang time
on the relay after it is unkeyed.
Adjusting The Receive Preamp
1. Remove the input and output coax cables for the amplifier radio and antenna connectors.
MAKE SURE YOU TURN THE TRANSMIT RADIO OFF.
2. Connect a coax from signal generator through a 5 dB pad to output connector on antenna
connector of amplifier. Set generator to mid-band 146 MHz with a -55dBm signal.
3. Connect a coax from spectrum analyzer to the radio input of amplifier.
4. Set spectrum analyzer to read 10dB per cm vertical deflection. Apply a 3cm reference signal
from generator (approximately -55dBm).
5. Turn on receive amplifier. Signal should increase 1.5 cm (15dB) with dip switch SW4 in LOW
gain position and 2.1 cm (21dB) in the HIGH gain position.
−NOTE: Because of the devices used, 12 dB gain is possibly all the gain that may be
achieved in a worst case event in the HIGH gain position.
6. If you do not have sufficient gain, adjust the variable capacitor C22 for 15 dB gain with S4 dip
switch in low gain position.

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Troubleshooting:
The Mirage B-108-G is designed for long, trouble-free performance and should not require
extensive troubleshooting in the field. Many causes of common malfunctions are eliminated by
the built-in protective circuitry.
−NOTE: In the event of automatic power shut-down, the amplifier must be turned off and the
cause of the shut-down determined and removed!
In case of difficulty, check the following before assuming amplifier malfunction:
a. Loose antenna or power supply connections
b. VSWR of antenna system
c. Coaxial cables from radio to amplifier, and amplifier to antenna
d. Output voltage of power supply
e. Power output of radio
f. Improper fuse rating
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 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.