Mirage B 2518 G
Contents
1. do NOT expect to run 160 watts PEP and have acceptable I MD performance In AM operation carrier power is normally 25 or more of the peak envelope power as indicated on a true peak reading meter Unmodulated carrier output power should not exceed 25 watts Peak envelope output power should not exceed 100 watts when measured on an accurate peak reading meter 4 1 Splatter and Distortion At low power levels amplifier gain is affected by bias settings If bias is set too low turning drive power down can actually make the ratio of distortion to signal worse not better This amplifier has an active bias system which forces the bias voltage to a fixed level This system is vastly superior to conventional resistor shunt diode bias for maintaining operating bias as drive power temperature and supply voltage varies At high power levels three main problems limit linearity and cause splatter All three problems are reduced or cured by turning the drive power down 1 Output device current amplification in this case transistors are used is a problem Transistors unlike most vacuum tubes show a gradual decrease in gain as drive level increases It is important this amplifier be operated in the area where the gain slope is linear or rounded in a sine curve to minimize splatter and IMD Maximum SSB peak power is approximately 110 watts This generally corresponds to an average power of 25 to 50 watts depending2. Control Cables Length of RF and control cables is not critical The RADIO connector of this amplifier is a SO 239 UHF Female UHF style connectors are perfectly fine at frequencies below UHF and have almost immeasurable loss at VHF and lower The amplifier input is matched for 50 ohms and the amplifier is very stable The input cable can be any reasonable length as far as the amplifier is concerned The ANTENNA connector is a SO 239 UHF Female The design load impedance is 50 ohms and any load with a VSWR under 2 1 The output cable must safely handle the full power of the amplifier and must have good connections Be sure connectors are installed and soldered properly and the coaxial cables are of reasonably good quality Control cables can be any length within reason because current is low The RELAY jack is used to manually place the amplifier in the transmit mode when it is pulled low to ground It is a conventional phono female connector also called RCA jack This type of connector is common with VCR s and other consumer electronic devices The current from this jack is less than 100 mA and the open circuit voltage is less than 15 volts There are no damaging back pulses from this jack it is fully buffered Never apply voltage to this jack 1 4 Mobile Mounting Considerations a Location Do not locate this amplifier in excessively warm locations near heater vents or in unventilated areas with ambie
3. on voice and compression characteristics 2 Output device voltage saturation caused by incorrect loading If the amplifier is not properly matched to the load the peak collector voltage can get too high This can not only cause splatter it can cause the output transistors to fail 3 As base current increases the base bias tends to shift negative Many or most amplifiers with conventional resistor shunt diode biased amplifiers actually move into class C a non linear mode as the drive power is increased This amplifier has active bias and doe not exhibit this problem In AM operation carrier output power is normally 25 or more of the peak envelope power as indicated on a true peak reading meter Unmodulated carrier output power should not exceed 25 watts 4 2 Drive Power To preserve signal quality in SSB and AM modes amplifiers must be operated in the linear portion of their gain curves Since this amplifier has no tuning adjustments the user can control only the load impedance SWR and drive power Many operators think RF power meters should show some fixed ratio of carrier or whistle power to speech power This is not correct The ratio varies greatly with many factors including the operator s voice Pushing up the drive power to see a certain output power on a meter that is NOT a true peak reading meter is a mistake Power should be measured on a true peak reading meter Many manufacturers marke
4. 6 6 6 Relay Chatters or Clicks off and on a RADIO and ANTENNA leads are reversed b Drive power is too low under 1 2 watt 6 7 Technical Assistance Technical assistance is available by calling xxxxxxx between the hours of x and x Please be sure you have check the obvious problems and that you have the model number and information about your radio and power meter available 6 8 Ordering Parts Parts are available direct from Mirage either by calling xxxx or writing to Xxxxx Please have a credit card number available over the phone do NOT include credit card information in the mail or prepay the order with a check after calling for prices Part numbers are listed after the schematic Be sure you have the full part description the model and serial number if used on this product and the part number 7 0 Schematic and Parts List 8 0 Warranty Terms and Disclaimers
5. IMD is the result of signals mixing in amplifiers or other less than perfect devices IMD results in signals appearing on entirely new frequencies This problem can occur either external to the receive system or internal to the receive system Every effort was made to make the preamplifier in this unit immune to overload The receiver may overload if signal levels from the preamplifier are stronger than the receiver can tolerate In some cases the preamplifier itself may be overloaded If paging or other commercial transmitters suddenly appear in the receiver while using the preamplifier try turning the preamplifier off In some cases reception may improve It is best to use the preamplifiers only when necessary and to avoid using them in congested areas with many strong transmitters nearby Be sure you are using the lowest gain setting possible figure XX unless the receiver actually needs a bigger gain boost Warning Never connect this unit backwards with the radio to the ANTENNA connector and the antenna to the RADIO connector If you do the preamplifier can be damaged Never use the preamplifier if the antenna is near other transmitters 6 0 In Case of Difficulty Always be sure the power is connected properly section 1 2 and the RF connections are correct section 1 3 6 1 Does not Transmit or Receive at all a Does the radio work OK with the amplifier removed from the system and replaced with a barrel connector wi
6. Mirage B 2518 G This compact rugged VHF RF power amplifier greatly improves signal quality and range This unit contains a low noise GASFET receiving amplifier a 160 watt power amplifier and associated control and protection circuitry This amplifier operates from any well filtered direct current 11 15 volt power source capable of supplying 30 amperes under full load The power source must be either negative grounded or totally ground independent Warning never use this unit with 1 positive ground supplies 2 vehicles having positive ground batteries 3 power sources exceeding 16 volts Always fuse power leads at the battery with 30 ampere fast blow fuses This amplifier has the following important features 1 Automatic RF actuated transmit and receive switching or manual switching 2 Active bias for greatly improved SSB linearity 3 Low noise GASFET receive preamplifier 4 True push pull circuitry and clean RF layout for excellent stability 5 Excess SWR and overdrive protection 6 Remote control capabilities 0 0 1 0 2 0 3 0 4 0 5 0 6 0 w N oo Table of contents QUICK CONNECT Read this section first no matter what Mounting Considerations 1 1 Cooling and Temperature Mobile or Fixed Location 1 2 Mobile mounting 1 3 Fixed or base mounting 1 4 Repeater operation Radio or exciter 2 1 Power level T R control or keying interface RF wiring connections and oth
7. ality 50 ohm coaxial cable Length and cable size is not important except as it might add signal loss if the cable is extremely long 3 0 FM CW and non linear modes Good linearity is the faithful reproduction of input power level changes by the output power of the amplifier Some modulation methods or operating modes do not depend on distortion free amplitude changes for transferring information Non linear modes include CW FM and FSK The amplifier can gain compress or flat top without changing signal quality or bandwidth because the RF is either on or off This allows the amplifier to be driven to higher output levels with no detectable change in signal bandwidth 3 1 Drive Power Drive power on FM CW or FSK is limited by power ratings of transistors and heatsink temperature The transistors are safely able to accept 30 watts of drive which corresponds to approximately 160 watts carrier output Do not trust unknown or questionable accuracy meters Some meters are off by as much as 50 or more 3 2 Duty cycle CW and FM The duty cycle is set by ambient temperature mounting position operating power and airflow Temperature and mounting concerns are detailed in section 1 0 Driving power concerns are detailed in section 2 0 The maximum amplifier output power on CW FM and FSK is 160 watts ICAS At the maximum power output of 160 watts this amplifier will normally provide a 33 long term duty cycle w
8. ble to run this unit at full power 1 0 Mounting Considerations To insure long life and optimum performance pay careful attention to mounting and wiring This unit comes with a mounting bracket for rigid mounting at home or in vehicles It also has rubber feet for use where movement is not a problem Warning never install this unit in areas where 1 ambient temperatures exceed 110 F 43 C 2 exposed to moisture excessive dust or dirt 3 subjected to mechanical shock or vibration 1 1 Cooling and Temperature Reduced operating temperatures almost always extend the life of electronic components If the heatsink becomes uncomfortable to touch the amplifier may require additional cooling If the heatsink becomes uncomfortable to touch the amplifier may require additional cooling Heatsink temperatures above 140 F indicate the need for additional cooling such as re mounting the amplifier in a cooler location or the addition of a small fan blowing on the heatsink Mirage has a cooling kit P N FK 18 This kit includes a 12 Vdc fan and mounting bracket NOTE As temperature in the mounting area increases especially if air is not moving cooling becomes less effective and the amplifier will run hotter If cooling is a problem the largest change will come from forcing air over the heatsink with a small fan The heatsink in this amplifier is sized for ICAS operation at 160 watts carrier outpu
9. chniques when using this amplifier for home or fixed operation 5 0 Receiving Preamplifier Pre Amp This amplifier contains an internal receiving amplifier also called a pre amplifier or pre amp that boosts weak signals It has a noise figure of about 1 dB and about 14dB maximum gain Gain is selectable by internal jumpers located on the small PC board between the red and black power leads figure xx These jumpers select approximately 14 8 and 5dB gain As a general rule even the lowest gain setting will provide more than enough gain 5 1 Signal to Noise ratio At 150 MHz the signal to noise ratio SNR of the received signal should easily be established at the antenna The required preamplifier noise figure varies greatly with the receiver bandwidth and antenna type as well as the location This preamplifier s noise figure is just over 1 dB which is more than adequate for normal antennas and normal bandwidths used in communications Noise power is inversely proportional to bandwidth and the noise figure of this amplifier will allow CW signals of less than 03uV and FM signals of less than 30uV to be detected with over 10 dB SNR A lower noise figure amplifier is seldom if ever necessary for terrestrial communications Since this preamplifier will put almost any system well into ambient noise no further improvement in sensitivity will result from more gain or lower noise figure 5 2 Intermodulation IMD Products
10. er Non linear Operation Drive power Duty cycle T R Control or keying Power Output Feedlines and antennas B and Linear modes Drive power Duty cycle 4 3 T R control or switching 4 4 Power Output 4 5 Bandwidth or spatter 4 6 Feedlines and antennas Receiving Preamplifier 5 1 Signal to noise 5 2 Intermodulation products In case of Difficulties 1 Transmitting 2 Receiving 3 Technical Assistance 4 Ordering parts N N PRMOWWWWWTAN NEPYWMUBRWNE SW Schematic and Parts Warranty Terms 0 0 Quick Connect 1 Mount or place the amplifier in a cool area The best mounting position will place the long length of heatsink fins vertical The amplifier must have sufficient cool air supply Do not mount in confined or hot locations or where exposed to moisture 2 Connect the power leads to the battery or power supply Be sure to fuse the red positive lead at the battery or power supply with a 30 ampere fuse The red lead must always be positive with an operating voltage of 12 15 Vdc We do NOT recommend connecting the black lead directly to a vehicle battery terminal Connect the black lead to the vehicle s chassis with a good solid connection 3 Connect the radio to the UHF style female RADIO connector with any length or type of good quality 50 ohm coaxial cable Any size or length 50 ohm coaxial cable will work on the INPUT just be sure the jumper is good 4 Connect the antenna or
11. ithout overheating Do not exceed 5 minutes total accumulated transmitting time without ten minutes of total accumulated resting time This is a rough guideline actual duty cycle limitations depend on many factors If possible especially if cooling might be marginal and there is no external air blowing across the heatsink mount the amplifier with heatsink fins vertical This allows natural convection to circulate air See section 1 0 for details Warning the safe maximum temperature of the heatsink is 140 F If the heatsink feels too hot to hold it is almost certainly too hot for safe operation 3 5 Feedlines and Antennas This unit will work with any antenna as long as SWR at the OUTPUT of the amplifier is less than 2 1 Warning never exceed 20 watts maximum reflected power Try to keep SWR below 2 1 Make sure all feedline and antenna connections are good 4 0 SSB and Linear Modes SSB and AM operation requires linear amplification of signals If the amplifier is not linear mixing products occur These mixing products make the signal bandwidth increase they are referred to as splatter Amplifier gain changes with power level One design goal of this amplifier was minimizing the effects of non linearity and reducing needless splatter Unlike tube amplifiers solid state amplifiers go into gain compression long before they saturate Even though this amplifier can produce 160 watts or more on carrier
12. nt temperatures exceeding 120 degrees Fahrenheit Do not install this amplifier in damp or wet locations Be sure air can circulate freely around the amplifier Do not cover the heatsink The best location for this unit is a well ventilated area inside the passenger compartment If the trunk area doesn t get too hot it can also be a suitable location Engine compartments should never be used to house this amplifier If possible mount the amplifier with the LONG length of heatsink fins vertical Figure xx This will allow natural convection to circulate air deeply through the cooling fins See section 1 1 for details on temperature b Wiring Make sure wiring is installed so wires are not pinched or cut The length of high current power and ground return leads is very important Keep the heavy dc power leads short as the installation permits This includes the ground lead to the battery or the vehicle s chassis Warning all leads power must be fused at the battery NEVER depend on fuses inside the unit for fire protection 1 Use a 30 ampere fast blow fuse at the battery positive connection 2 Ground the negative lead to a good ground on the vehicle s sheet metal 3 Never obtain main supply power from under dash vehicle wiring 4 If the negative lead is connected directly to the battery instead of the vehicle chassis or sheetmetal it must be have its own 30 ampere fuse installed at the battery NOTE The length of
13. pecially if cooling might be marginal and there is no external air blowing across the heatsink mount the amplifier with heatsink fins vertical This allows natural convection to circulate air See section 1 0 for details Warning the safe maximum temperature of the heatsink is 140 F If the heatsink feels too hot to hold it is almost certainly too hot for safe operation 4 4 T R Control or Switching This amplifier has an internal RF sensing system that turns off the pre amplifier and places it in the transmit mode A front panel MODE switch activates an internal hang delay timer for SSB or CW operation This hang time allows the relays to remain energized without input power for a few seconds The hang time is controlled by R8 located at the front and center of the board behind the MODE switch Delay is normally set for 1 second at the factory 4 5 Power Output The maximum power output for clean linear SSB service is 110 watts PEP Antenna SWR should be as low as possible The 13 8 volt 30 ampere power source must not have hum or ripple The voltage should have less than 0 2 volts sag under full load for best linearity 4 6 Antennas and Feedlines Any antenna and 50 ohm feedline can be used providing it presents less than 2 1 SWR to this amplifier Linearity and splatter will be better controlled if SWR is as low as possible with a 1 1 SWR ratio unity SWR being ideal Be sure to use proper lightning protection te
14. power meter to the ANTENNA connector through any length of good quality 50 ohm coaxial cable capable of handling 200 watts of power Any size or length 50 ohm cable will work as long as losses are acceptable The cable must safely handle 200 watts at 150 MHz Be sure connectors are installed and soldered properly 5 The switches in this unit are self explanatory They are MODE PRE AMP and POWER a The MODE switch adds time to the transmit relay in the SSB CW position This allows SSB or CW operation without excessive relay chatter or word chopping It is normally not necessary to use the SSB CW mode position when using the RELAY port for relay control b The PRE AMP switch adds a low noise receiver pre amplifier which improves signals if receiver gain is marginal In congested areas it may be advisable to NOT use the pre amp to reduce receiver overloading c The POWER switch controls the transmitting amplifier and resets any overloads 6 The FAULT light illuminates whenever excessive drive power from the radio is applied or reflected power from the antenna exceeds a preset value This light indicates the protection circuits have locked on preventing the amplifier from keying If the FAULT indicator is on you must check drive power and antenna reflected power Drive power must be below 30 watts and Reflected power must be below 20 watts at full output If SWR is over 2 1 it is unaccepta
15. r chassis ground conductors carry full operating current This current can reach 30 amperes For maximum power output it is important to minimize the voltage drop along these conductors For maximum output power all high current leads including the ground lead should be kept as short as reasonably possible Be sure connections are good Never extract this power from under dash wiring unless the vehicle manufacturer tells you it is safe A fuse is must always be installed at the battery to prevent wiring fires If a fuse is not added you run the risk of a fire if the wiring is accidentally shorted between the battery and amplifier NEVER omit this fuse no matter how safe you think it is Suitable fuses and holders are generally available from electronics car stereo and automotive parts stores This device requires a 30 ampere fuse The following chart gives the approximate peak voltage drop in volts per foot of a single supply wire with 30 amperes of current This chart assumes the negative return to the battery through the vehicle chassis has the same resistance as the positive lead or that a home power supply uses equal length and size conductors for positive and negative ground leads AWG Voltage Drop Maximum Length For single at 30 amps Full Performance conductor For best performance voltage drop in high current positive and ground leads should be limited to 0 5 volts or less at maximum current of 30 amperes 1 3 RF and
16. t meters that are not actual peak reading meters even though they call the meters peak reading If you have a meter like that you will find it impossible to properly determine drive settings on SSB using the meter If you do not have a true peak reading meter either an oscilloscope or off the air reports can be used to determine if you are driving the amplifier too hard The proper drive power for this amplifier is a drive power allowing output power peaks to reach approximately 2 3 of the saturated output power as measured on a true peak reading meter Maximum power output for good linearity is 110 watts PEP as indicated on a properly working PEP reading meter In AM operation carrier output power is normally 25 or more of the peak envelope power as indicated on a true peak reading meter Unmodulated carrier power should not exceed 25 watts peak envelope power on AM should not exceed 100 watts or so 4 3 Duty Cycle The duty cycle of this amplifier is limited by temperature considerations In normal AM or SSB operation the duty cycle is set by ambient temperature mounting position operating power and airflow Temperature and mounting concerns are detailed in section 1 0 Driving power concerns are detailed in section 4 2 The maximum PEAK amplifier output power on SSB and AM is 110 watts PEP At the maximum power output of 110 watts this amplifier will normally provide a 100 duty cycle without overheating If possible es
17. t with a 33 long term duty cycle Do not exceed 5 minutes total accumulated transmitting time without ten minutes of total accumulated resting time This is a rough guideline actual duty cycle limitations depend on many factors On SSB and AM because power is greatly reduced the duty cycle is much longer The general guideline is to watch the heatsink temperature and improve cooling or reduce duty cycle if the heatsink is uncomfortable to touch If possible especially if cooling might be marginal and there is no external air blowing across the heatsink mount the amplifier with heatsink fins vertical This allows natural convection to circulate air 1 2 POWER WIRING This amplifier has two main power leads The red lead connects to the floating not grounded positive 12 15 Vdc battery or power supply terminal The black lead is the negative lead It is grounded inside the amplifier and is common with the metal case and all connector grounds To reduce fire hazards or the chance of equipment damage the red lead must always be fused with a 30 ampere fuse at the battery Some power supplies have internal current protection Power supplies without current limiting must be protected by properly sized fuses located at the supply The black lead should connect to the negative terminal through the vehicle chassis We do not recommend connecting the black lead directly to a battery post The heavy RED conductor and black battery return and o
18. the cable supplied with the remote control head P N xxxxx is not critical The RF cables should not be excessively long although they are not critical 1 5 Home or Fixed Installations Mount the amplifier in any location that is cool and has air circulation It is best to mount this unit with the long length of the heatsink fins vertical For extended duty you may want to add a cooling fan See section xxx The amplifier should be mounted as close to the power supply as possible Section 1 2 details wiring considerations The power supply should be fused or have internal current limiting at a maximum current of 35 amperes It should be well filtered and voltage regulated at no more than 15 volts dc A power supply with a crowbar or over voltage protection system is a good idea in case supply regulators fail Be sure to ground the case of the unit to the station ground buss with a heavy short lead Lightning protection is a good idea but the safest solution is to disconnect all antennas and unplug all equipment when not being used 1 6 Repeater Mounting Please check with the factory before using this unit for repeater use As of the date of this manual this unit if cooling is assisted with a fan appears to be suitable for repeater use The push pull design with transmission line type matching sections makes it stable and reliable During repeater operation output power must be reduced to 50 watts approximately 3 watts of dri
19. thout changing anything else If so read section 1 2 The coax connectors that attach to the amplifier or the amplifier may be the problem b If the radio does NOT work ok you probably have a bad jumper cable or bad coaxial cable 6 2 Nothing lights or seems to work a Check the power wiring and fuses The amplifier has an internal fuse also b Read section 1 2 6 3 Transmits OK does not amplify receive a If this unit fails transmits OK but fails to make a difference on receiving weak signals and the Preamp light illuminates it may have a defective preamplifier b If the XMIT light remains illuminated when receiving try unplugging any CONTROL or RELAY wiring If that corrects the problem you have a wiring or control system problem 6 4 Receives OK does not amplify transmit a Does your radio transmit OK without the amplifier removed and replaced with a barrel connector If not see 1 3 2 4 4 4 b Is SWR okay both with the amplifier in line and out of line See 3 5 4 6 6 5 Continuously Trips FAULT light a Check transmitter power Be sure to check the PEAK power because some radios transmit a pulse greatly exceeding the continuous power If your radio has this problem it is unsuitable for any amplifier because it will eventually damage the amplifier s transistors See sections 2 1 3 1 and 4 2 b Check the SWR and reflected power Look for bad cable connections See sections 1 3 2 4 3 5 and 4
20. ve power The cooling system must be augmented with forced air using the Mirage FK 18 cooling kit or a similar product It is important to use good installation techniques 2 0 Radio or Exciter This amplifier will work with almost any exciter or radio operating between 140 and 150 MHz The most important guidelines are detailed in the following sections 2 1 Drive Level The radio or exciter used to drive this unit should have an output power between Ye and 25 watts Do not drive this unit with more than 30 watts on FM 2 watts carrier on AM or 10 watts PEP on SSB about 3 watts average power 2 2 Duty Cycle The duty cycle of this unit is primarily limited by heatsink temperature The more power output and hotter the ambient temperature the more important cooling becomes See section 1 1 2 3 T R Control or Keying This unit contains an internal RF sensing system This system will automatically disconnect the receiving pre amplifier if being used It also places the unit ina transmit mode when the POWER switch is ON The rear panel female phono RCA jack labeled RELAY can be used to manually force this unit to switch into a transmit mode If the PRE AMP switch is on the pre amplifier will be switched off when the RELAY line is pulled low grounded If the POWER switch is on the internal transmitting relays will switch to the transmit mode 2 4 Wiring The exciter can be connected to the amplifier with any type of good qu
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