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Midland 70-066 low Band Conversion to 6 Meters:  Part 1                       Page 1 

 
 
 
 
 

Midland 70-066 

 

Conversion 

 

To 

 

6 Meters 

 

Introduction 

 

Ver 1.8 – 

07 Nov 2009

 

 

Part 1 

 

Rod McCosker VK2DOT 

 
 
 

 
 

Summary of Contents for 70-066

Page 1: ...Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 1 Midland 70 066 Conversion To 6 Meters Introduction Ver 1 8 07 Nov 2009 Part 1 Rod McCosker VK2DOT ...

Page 2: ...ftware Part 2 The Synthesizer Board including EPROM board Z 273 EPROM Board The Synthesizer Board Synthesizer Alignment Part 3 Receiver RF Front end The Receiver Board Receiver Alignment AWA RT85 Receiver Board Top Assembly View AWA RT85 Receiver Board Bottom Capacitor View Part 4 Transmitter PA Circuit The Transmitter PA board Transmitter Alignment Part 5 The RT 85 Transceiver Block Digram Receiv...

Page 3: ...ofile 16 pin Capacitors Jaycar 2 2pf 2 of RC 5304 Note All capacitors are 50V Ceramic 5 6pf 3 of RC 5309 8 2pF 2 of RC 5311 22pf 5 of RC 5216 100pf 1 of RC 5324 1000pf 1 of RC 5336 Note If you acquire your capacitors from Jaycar Electronics then please check the capacitor values in each packet It has been found the wrong values has been added to packets of capacitors For the first few weeks of the...

Page 4: ...ociated 2716 EPROM Then burn the EPROM return it to the Z 273 PCB via a 2 pin socket Else program the Z 273 via the Z 273 PCB programmer Synthesizer Modification Remove PCB board remove coil make coil replace board place capacitors onto underside of board synthesizer alignment and replace PCB board into transceiver In this part you will use test equipment Ie Frequency counter DC meter Plus tuning ...

Page 5: ...s 70 066 ST1 66 80 mhz 40 watt 80 Dash Mount mid band 70 076 ST1 66 80 mhz 40 watt 80 Trunk Mount mid band Models A 66 80 Mhz B 75 88 Mhz Above Midland 70 066 Front View Above Midland 70 076 Front View Above Midland 70 076 Case View Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 5 ...

Page 6: ...Above Bottom View Above Top View Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 6 ...

Page 7: ...Gold Coast NZ Mt Climie NE Wellington 12 1 53 825 52 825 Repeater VK7RAD Tas Hobart VK7RNW Tas Ulverstone N W Coast 13 1 53 850 52 850 Repeater VK2RWI NSW Dural Sydney NZ Christchurch 14 1 53 875 52 875 123 Repeater VK2RBM NSW Lawson Blue Mts VK7RAA Tas Mt Barrow N Tas 15 1 53 900 52 900 Repeater VK3RMS Vic East Melbourne 16 1 53 925 52 925 Repeater VK1RGI ACT Mt Ginini ACT SE NSW VK4RBX Qld Ipswi...

Page 8: ...mplex Channels 44 0 53 125 53 125 45 0 53 150 53 150 WICEN 46 0 53 175 53 175 47 0 53 200 53 200 48 0 53 225 53 225 49 0 53 250 53 250 50 0 53 250 53 275 51 0 53 300 53 300 52 0 53 325 53 325 53 0 53 350 53 350 54 0 53 375 53 375 55 0 53 400 53 400 56 0 53 425 53 425 57 0 53 450 53 450 58 0 53 475 53 475 59 0 53 500 53 500 60 0 53 525 53 525 Repeater Simplex 61 0 53 559 53 550 ...

Page 9: ...to the surface to be de soldered with a small brush old toothbrush or icy pole stick We have found that a wooden tooth pick has been the most successful method of applying the Bugs Juice to the pin requiring de soldering Midland Land Mobile Model and Features Table for 70 066 70 076 Syntech I Model Type Split Power Channel Count Comments 70 066 ST1 66 80 mhz 40 watt 80 Dash Mount mid band 70 076 S...

Page 10: ...ly coupled to a Frequency counter Measure the Frequency and power out Callsign Date Frequency Power Out Then Connect your transceiver to a signal generator and adjust the signal generator to the above noted frequency Adjust the mute to just close then measure the micro volts for mute opening for receiver sensitivity Rx Sensitivity If all of the above are OK then you may continue with the conversio...

Page 11: ... UHF connectors RF cable Transceiver to Signal Generator RG58 BNC to UHF connectors DC cable for receiver testing 2 pin connector to 2 of red banana plugs for DC meter DC cable for synthesizer testing 1 cable black banana plug to alligator clip 1 cable red banana plug to red clip UV Light assembly for bulk erasing of Z 273 s 2716 EPROM s ...

Page 12: ...The Synthesizer including EPROM Board Midland70 066 Sync Board Top View below Remove the EPROM board above as Z 273 reverse view below Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 12 ...

Page 13: ...he US for approx 450 US or 2 Remove the Z 273 board from the Synthesizer Board Then remove the 2716 EPROM using de soldering equipment from the EPROM board Then solder a low profile 24 pin socket to the EPROM board Reprogram EPROM with 6 meter firmware by using the VK2DOT Midland software or any other software 3 Using the VK2DOT Z 273 adapter as shown in section 5 Remove the Z 273 board from the S...

Page 14: ...ard from the transceiver assembly Midland 70 066 Sync Board Top View below TX buffer remove L114 and keep for use on the PA board replace with 7 5 turns of 0 5mm wire same diameter former Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 14 ...

Page 15: ...Midland 70 066 Sync Board Bottom Unsolder Bottom Plates Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 15 ...

Page 16: ...X main VCO add 22pF to C709 TX offset VCO add 22pF to C137 for Midland 70 066 located under VCO cover on the track side of the board Some transceivers may require more RX buffer amp add 5 6pF to primary of L709 Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 16 ...

Page 17: ...Midland 70 066 Sync Board Bottom View New Capacitors below Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 17 ...

Page 18: ...M set to channel 48 53 225Mhz 3 Use the correct alignment tool on all ferrite cores the ferrite slugs are easily broken Connect DC Voltmeter between ground and TP701 On 10 Volt Range Adjust L702 such that the de voltage at TP701 is centered on 3 5V for all programmed channels i e some above 3 5V and some below 3 5V Voltages will swing between 2 Volts and 4 Volts 4 Ensuring that the exciter output ...

Page 19: ...Receiver Local Oscillator output from J365 Midland 70 066 low Band Conversion to 6 Meters Part 1 Page 19 ...

Page 20: ...Midland 70 066 low Band Conversion to 6 Meters Introduction Part 1 Page 1 1 Midland 70 066 Conversion To 6 Meters Ver 2 9 16 Nov 2009 Part 1 Rod McCosker VK2DOT ...

Page 21: ...nthesizer Board including EPROM board Z 273 EPROM Board The VK2DOT Z 273 Adaptor The Synthesizer Board Synthesizer Alignment Part 3 Receiver RF Front end The Receiver Board Receiver Alignment Midland 70 066 Receiver Board Top Assembly View Midland 70 066 Receiver Board Bottom Capacitor View Part 4 Transmitter PA Circuit The Transmitter PA board Transmitter Alignment Part 5 Midland 70 066 Transceiv...

Page 22: ...NOTE PLEASE READ THIS DOCUMENT It has been noted that the majority of mistakes have been caused by users NOT reading this documentation before or during the conversion If any mistakes are found or a suggestion for a better document please send your comments to vk2dot tpg com au ...

Page 23: ... Needed IC Socket Low profile 24 pin 1 of Jaycar PI 6506 If you do not have a Z 273 burner All Midland 70 066 Parts Needed Capacitors Jaycar 2 2pF 2 of RC 5304 Note All capacitors are 50V Ceramic 4 7pF 1 of RC 5308 5 6pF 3 of RC 5309 8 2pF 3 of RC 5311 22 pF 7 of RC 5316 27 pF 2 of RC 5217 33 pF 1 of RC 5218 39 pF 2 of RC 5219 100 pF 1 of RC 5324 1000 pF 1 of RC 5336 Note If you acquire your capac...

Page 24: ...F ceramic Capacitors Jaycar RC 5216 1 of 5 6pF ceramic Capacitor Jaycar RC 5309 1 of 24 pin low profile socket Jaycar PI 6506 Approximately 100 mm of 0 63mm 22bs enameled coated wire Jaycar WW4018 Masking Tape Marking Pen for putting coil numbers on Masking tape in synthesizer section and marking panels PCB s Drill Bit Size 5mm Small plastic bag to keep screws and coils in A4 plastic bag to keep c...

Page 25: ...ram the 2716 EPROM place into the 22 pin socket Synthesizer Modification Remove PCB board remove coil make coil replace board place capacitors onto underside of board synthesizer alignment and replace PCB board into transceiver In this part you will use test equipment ie Frequency counter DC meter Plus tuning tools Receiver Modification Remove PCB board solder place capacitors onto underside of bo...

Page 26: ...ynthesizer Coil De solder synthesizer coil from Synthesizer PCB Add new L114 coil Capacitors C137 C709 C across L709 Place synthesizer board back into transceiver Insert Z 273 PCB into Synthesizer board attach cable to PCB Align synthesizer Receiver board Partially remove receiver board from the transceiver Leave power connections connected Add capacitors to receiver PCB Place receiver PCB back in...

Page 27: ...70 066 ST1 66 80 mhz 40 watt 80 Dash Mount mid band 70 076 ST1 66 80 mhz 40 watt 80 Trunk Mount mid band Models A 66 80 Mhz B 75 88 Mhz Above Front View of Midland 70 066A with Local Head Above Bottom View of Midland 70 066A with Local Head Midland 70 066 low Band Conversion to 6 Meters Introduction Part 1 Page 1 8 ...

Page 28: ...Above Midland 70 076 Case View Above Midland 70 076 with Remote Head Midland 70 066 low Band Conversion to 6 Meters Introduction Part 1 Page 1 9 ...

Page 29: ...ove Bottom View of Midland 70 066 Receiver side with Local Head Above Top View of Midland 70 066 Receiver side with Local Head Midland 70 066 low Band Conversion to 6 Meters Introduction Part 1 Page 1 10 ...

Page 30: ...ast 08 1 53 7250 52 7250 123 Repeater VK2RAG NSW Central Coast 2012 we think VK4RGA Qld Gladstone VK4RLB Qld Woodridge BrisbaneSouth VK3RGV Vic Shepparton NZ Auckland 09 0 53 7500 52 7500 Repeater VK5RSB SA Summertown Adelaide NZ Wellington 10 0 53 7750 52 7750 Repeater VK5RLZ SA Adelaide North VK4RRC Qld Redcliffe N Brisbane VK4RBG Qld Bundaberg VK4RBP Qld Atherton Tableland 11 0 53 8000 52 8000 ...

Page 31: ...3 9000 Reverse channel 15 36 0 52 9250 53 9250 Reverse channel 16 37 0 52 9500 53 9500 Reverse channel 17 38 0 52 9750 53 9750 Reverse channel 18 Data Channels 39 0 53 0000 53 0000 40 0 53 0250 53 0250 41 0 53 0500 53 0500 42 0 53 0750 53 0750 43 0 53 1000 53 1000 Voice Simplex Channels 44 0 53 1250 53 1250 45 0 53 1500 53 1500 WICEN 46 0 53 1750 53 1750 47 0 53 2000 53 2000 48 0 53 2250 53 2250 4...

Page 32: ... up this Bugs Juice Crush lumps of rosin and place in a jar or a small tin can with an air tight lid Cover the rosin in the jar or can with methylated spirits Apply the air tight lid and allow to dissolve If the final solution is too thick then thin with more methylated spirits If the final solution is too thin then thicken by adding more rosin Apply to the surface to be de soldered with a small b...

Page 33: ...oftware will operate under DOS or Windows from a floppy or hard drive or from a USB stick Software works for AWA RT85 Low Band and Midland 70 066A or B for 6 Meters The CTCSS for the Midland 70 066 works The CTCSS for the AWA RT85 has to be checked The 10Khz and 12 5Khz Frequency step has not been checked Bands other than 6 Meters have to be checked Power Plug NOTE If you do not jumper pins 5 6 yo...

Page 34: ...tor WW s are opposite red black power leads Brown lead is internal speaker loop In the photo above the WW s are closest to the heat fins Midland 70 066 low Band Conversion to 6 Meters Introduction Part 1 Page 1 15 ...

Page 35: ... to gain access to the fins When both fins are pushed down the pin will retract from the rear of the socket Feed the new power cable through the Molex socket and through the socket end of the pin soldering the cable to crimp area Now open the fins slightly and pull cable back to lock the pin into position The same can be carried out for the speaker jumper for those who are not using remote speaker...

Page 36: ...arp object between legs That is how you count turns on a coil Remote cable for Midland 70 076 Head NOTE Connectors are reversed at the ends of the cable Computer cables work OK Midland 70 066 low Band Conversion to 6 Meters Introduction Part 1 Page 1 17 ...

Page 37: ...Generator to cover 50Mhz to 88Mhz Testing Hopefully your Midland 70 066 has an installed EPROM And the EPROM has not been erased If this is TRUE then Connect your transceiver to a 12 Volt power supply and the antenna to power meter and dummy load Go to channel 1 Press the transmit button to allow the power out to be loosely coupled to a Frequency counter Measure the Frequency and power out Callsig...

Page 38: ...n Modify the Z 273 EPROM PCB part 1 the synthesizer part 1 the receiver part 2 and the transmitter PA part 4 CCARC TEST CABLE s to be BUILT RF cable Transceiver to Power Meter RG58 Type N to UHF connectors RF cable Transceiver to Signal Generator RG58 BNC to UHF connectors DC cable for receiver testing 2 pin connector to 2 of red banana plugs for DC meter DC cable for synthesizer testing 1 cable b...

Page 39: ...Synthesizer including EPROM Board Midland 70 066 Sync Board Top View below Remove the EPROM board above as Z 273 reverse view below Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 3 ...

Page 40: ...idland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 4 REMEMBER to REPLACE the EPROM in the RIGHT WAY on the Z 273 or the EPROM will blow be USELESS Previous converters have done this ...

Page 41: ... frequencies 1 Using a MRP70 1000C MRP 70 programmer box and software This method allows you to program the EPROM on the Z 273 board without de soldering the EPROM from the Z 273 board The programmer box can be purchased in Australia for approx 300 or from the US for approx 450 US or 2 Remove the Z 273 board from the Synthesizer Board Then remove the 2716 EPROM using de soldering equipment from th...

Page 42: ...mbly Midland 70 066 Sync Board Top View below TX buffer remove L114 and keep for use on the PA board replace with 7 5 turns of 0 63mm wire same diameter former Use a 5mm drill bit to wind the new coil on Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 6 ...

Page 43: ...ttom Unsolder Bottom Plates It is noticed that the Midland 70 066A B models have only one shield on the bottom of the synthesizer board the left one above Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 7 ...

Page 44: ...VCO add 22pF to C709 TX offset VCO add 22pF to C137 for Midland 70 066 located under VCO cover on the track side of the board Some transceivers may require more RX buffer amp add 5 6pF to primary of L709 Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 8 ...

Page 45: ...Midland 70 066 Sync Board Bottom View New Capacitors below Re solder bottom plates back onto bottom of Sync Board Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 9 ...

Page 46: ...Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 10 ...

Page 47: ...Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 11 ...

Page 48: ...lume controls so that the loudspeaker is muted If the Phase Locked Loop PLL is unlocked the channel display will show 95 alert tone will be sounded and the dc voltage at TP701 will be 6 V or less than 1 7 V You have a problem If the PLL is locked either the first channel number will be displayed or else the unit will wait blank on channel 01 for Midland 70 066A until either the UP or DOWN button i...

Page 49: ...cy then 73 925Mhz Rx Oscillator frequency 3 Transmitter VCO Alignment Ensure that the exciter output is disconnected at J366 Connect the frequency counter to J366 The transmitter output local oscillator frequency will be at the transmitter frequency Ie for channel 48 will be 53 225Mhz when transmitting A The main transmitter VCO should be adjusted on the highest transmitter programmed frequency Ad...

Page 50: ...Receiver Local Oscillator output from J365 Midland 70 066 low Band Conversion to 6 Meters Synthesizer Part 2 Page 2 14 ...

Page 51: ...normal 10 Khz deviation signals they will sound distorted get the sending operator to back off from the microphone The Receiver Board Partially remove the receiver board from the Midland 70 066 transceiver below ie Remove all white plugs connected to the white sockets on the board Then remove all screws holding the receiver board to the transceiver chassis NOTE Do not unsolder the power cables to ...

Page 52: ... below Midland 70 066A Receiver Board Bottom Capacitors Added below NOTE Above C203 C211 has been changed to 2 2pF for the Midland 70 066A Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 2 ...

Page 53: ...PCB Unplug all plugs from the Receiver sockets NOTE The power cables are left Remove Receiver PCB and bend back to view bottom of board Rx Front end Add 22pF to C202 C205 and C212 Short C210 Add 2 2pF to C203 and C211 Add 8 2pF to C201 C206 and C213 LO tuned buffer Add 5 6pF to C220 and C223 Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 3 ...

Page 54: ...203 C211 has been changed to 2 2pF for the Midland 70 066A NOTE Above C211 has been changed to 2 2pF for the Midland 70 066A Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 4 ...

Page 55: ...Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 5 ...

Page 56: ...Midland 70 066 Receiver Board Bottom Capacitors below see larger diagram at end for printout Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 6 ...

Page 57: ...Midland 70 066 Receiver Board Top Assembly View below Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 7 ...

Page 58: ...Midland 70 066 Receiver Board Bottom Capacitor View below Midland 70 066 low Band Conversion to 6 Meters Receiver Ver 2 1 20 nov 09 Part 3 Page 3 8 ...

Page 59: ...erator to the Midland 70 066 antenna socket Connect a multi meter or DVM to Monitor CM202 pin 2 and peak L201 L202 L204 and L205 for maximum reading while remaining in the linear range ie Set signal generator level for positive meter reading before limiting occurs Note the reading at this pin will be negative until sufficient RF input signal is available Repeat adjustments for optimum An alternati...

Page 60: ...age applied to the PA stage will determine your output power Eg 25 Watts with 12 0 Volts 38 Watts with 13 8 Volts 3 It has been noticed that some converters have accidentally removed a or some Surface Mounted Components while de soldering coils etc from Printed Circuit Boards This has resulted in circuits not tuning correctly or especially the PA board self oscillating on another frequency other t...

Page 61: ...CB Printed Circuit Board is fixed to the chassis Remove the top cover from the PA PCB Unscrew the three screws from transistors Q503 Q502 Remember when placing PA PCB back into housing to use temperature transfer compound on bottom of transistors Remove the 6 screws from the side of the PA PCB Remove the PA PCB from its enclosure Unsolder the 3 wires from the PCB T8V B G Mark the PCB with your cal...

Page 62: ... soldering station You may wind all new coils or use the old removed coils If you intend to insert old coils then on de soldering the coils mark each old coil with marking pen and label masking tape tag attached to the old coil Remove L515 L516 L517 and L518 Since these coils will not be reused use side cutters to cut them in half and then remove the pieces by heating the joint from the underside ...

Page 63: ...114 from the synthesizer board 4 5 Turns Remove L503 and keep replace with original L501 3 5 Turns Remove L507 then replace with original L503 do not keep coil L507 just removed 2 5 Turns Remove L519 Cut back to 2 5 turns and keep coil to replace coil L513 Remove L513 and keep replace with old cut back 2 5 turns of coil L519 2 5 Turns Remove original L512 replace with original L513 1 5 Turns Midla...

Page 64: ...Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 5 ...

Page 65: ...bove Add 33pF to bottom of RV502 on the underside of the board for a Midland 70 066 Add 1 5pF to the RF sensor circuit C554 on the underside of the board as per the photo On the RT85 this capacitor is already fitted Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 6 ...

Page 66: ...ut in a good dummy load with a power meter not an antenna Set RV502 fully clockwise for maximum power out Key the transmitter and adjust for maximum power starting from the output end and working back towards the synthesizer Don t forget CV102 on the synthesizer board After modification and tuning it is normally possible to get 50W out of the transmitter with no sign of instability do not run it a...

Page 67: ...6 Transceiver to 6 Meters PA Swung Back Midland 70 066A Top cover still on Above PA Top View Midland 70 066A Original Setup Cover Removed Above Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 8 ...

Page 68: ...03 and keep replace with original L501 Remove L507 replace with original L503 do not keep coil L507 just removed Remove L519 Cut back to 2 5 turns and keep coil to replace coil L513 Remove L513 and keep replace with old cut back 2 5 turns of coil L519 Remove original L512 replace with original L513 Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 9 ...

Page 69: ...lace 27 pF across C525 Place 33 pF across C526 Place 100 pF across base ground of Q502 2SC1971 Place 1000 pF across base ground of Q503 2SC2097 Place 39 pF across CV501 Place 22 pF across CV502 Place 39 pF across CV503 Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 10 ...

Page 70: ...itors for Midland 70 066 Above Top of C526 33pf scrape green off copper layer PA Bottom View New Capacitors for Midland 70 066 Above Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 11 ...

Page 71: ...PA Bottom View New Capacitors for Midland 70 066 Above Top of C526 33pf scrape green off copper layer Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 12 ...

Page 72: ...PA PC Board Top View Above PA PC Board Top View Above Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 13 ...

Page 73: ...nnect a lower power 50 ohm power meter to J366 exciter output Go to channel 48 for center frequency Connect a multimeter to TP101 refer to the diagram above The Synthesizer Board and operate the microphone PTT button Midland 70 066 low Band Conversion to 6 Meters Transmitter PA Part 4 Ver 2 2 21Nov09 Page 14 ...

Page 74: ...or maximum power 6 Adjust RV502 to obtain Po 25W High Power position Note that the power rises slightly as the unit heats up so adjust for 23 24W when cold 7 If low power output is required short P302 to P303 on the control unit and adjust RV501 for required output 8 Also check at the lowest highest frequencies channel 19 52 500Mhz an channel 38 53 975Mhz Transmitter Audio Adjustments 1 Adjust aud...

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