XTR Mobile Information

40 watt VHF or 30 watt UHF Dash Mount with SCAN

If you have a model 70-1336x or 70-1526x , it is an XTR 8 Channel.  click here for specific information about this model. 

70-1340/1440 vs 70-1342/1442

According to recent information posted on the MidlandLMR group, the 1340/1440 radios do not have full TX bandwidth coverage at 40 watts.  They are 24 mhz wide @ 30 watts output and 12 mhz wide @ 40 watts output.  Also the 1340/1440 was sold as an economy model without the scan option.  Usually these radios only have a MON button on them.  Dealers would upgrade the radio by installing the scan option - adding the buttons and changing the eustachian  of the radio as these parts were the only things needed.  The 1342/1442 radios were 24 mhz TX bandwidth @ 40 watts and came with the scan option.  When converting to amateur use, the power on all XTR radios should be turned down to around 10 to 15 watts to avoid overheating the PA as the 40 watt power rating is for a 5% on time and hams are usually long winded.  If you run the PA at full power for extended periods of time, you will toast it. 

Talk Around Option

Occasionally you will see a radio or control head with a button labeled TA,  This button allowed simplex (talk around) operation on a repeater channel and did not require programming a 2nd channel in the radio for simplex.  This option requires internal jumpering on option connectors to enable the function.  Adding the button or connecting a control panel with the button to a radio does not enable the function.  On the CPU inside the radio a line is pulled low to enable talk around so it is possible to add it to the radio with just a on/off switch.

Parts Interchangeability

Control Heads - Trunk Mount Radio

  ST1 (Syntech I) and ST2 (Syntech II) control heads cannot be used on XTR trunk mount radios.  The XTR head is black with black trim.  

Control Cables - Trunk Mount Radio

ST1 and XTR control cables are interchangeable.  There are two types,  Flat ribbon and round cables. Many aftermarket cables are the flat ribbon type.  ST2 cables are not compatible and will not plug into the radio.

Power Cables

Dash mount radios use a 9 pin molex connector.  A jumper must be installed to enable the internal speaker.  If an external speaker is  used, no jumper will be installed and a pair of wires will connect to the external speaker from the connector.   Refer to the wiring diagram for hookup information.  If no CTCSS hang-up box is used, a jumper should be installed in place of the hang-up box.  

Trunk mount radios use (2) 9 pin molex connectors.  One on the control head and one on the radio.  Refer to a wiring diagram for power, jumpers, and speaker connection.  Trunk mount radios may require power on both plugs for proper radio operation and programming.  Some radios are wired that the control head must be powered before the radio will transmit. This is called ignition sense. If you do not have power to the control head and the radio will not key (red LED comes on), connect power to the control head. 

Replacement power and control cables may be purchased from Bridgeman Communications and they have wiring diagrams available on their website.

Microphones

  The standard Midland mic will interchange between ST1, ST2, and XTR radios but the connector on some radios is a 6 pin instead of 4 pin.  4 pin CB connectors are direct replacements for the 4 pin connectors but most 6 pin CB connectors  have one pin offset and will not plug into the Midland 6 pin jack.  Currently a source of the Midland 6 pin connector is not known.  

Mounting Brackets

Dash mount ST1 mounting brackets will not work on dash mount XTR radios.  Dash mount ST2 and   dash mount Titan brackets will work on the XTR.

Rear mount radios use a tray but the front mount bracket can be used on one. 

Channel Expansion

XTR radios can be upgraded from 22 channels to 99 channels by adding a memory module.  These are no longer available from Midland.  It plugs in near the microprocessor.  In the picture above, the metal cover is removed and you can see the top of the CTCSS board and the location of the option slot.  Do not program more than 22 channels unless the memory expansion module is present.  Please don't email me asking if I have any for sale.  They appear on Ebay and occasionally on the MidlandLMR list. 

Converting to other frequency ranges

These radios will go out of band with editing of the software and/or the radio code plug.  A tutorial is located in the MidlandLMR Yahoo Group files section. 

XTR Band Ranges

Editing the DOS files will allow programming a radio out of its range.  In the case of a Hiband VHF radio, the model can be changed to an A range radio (136-150 mhz) or left as a B range and the software frequency range modified. 

The VCO usually requires tweaking to lock within a new frequency range.   VCO unlock is indicated by E3 blinking on the display and an alert tone. VHF "B" radios will cover 2 meters and UHF "B" radios will cover 440-450.  More tuning than just the VCO adjustment may be required for peak performance. 

The 70-0351C model can be put on 6 meters with some retuning of the front end and modification of the low pass filter on the antenna output.  The shield cover over the front end coils must be removed. More to come soon on this modification.

Repairing Display Problems on XTR Mobiles -  The display driver chip is no longer available.  If you have a problem with your dash mount radio, the control and display panel from a trunk mount head can be removed and replace the the circuit boards in the dash mount radio.  You must remove the electrolytic 25 volt 470 uf axial lead C307 capacitor from the control panel from the bad dash mount radio and install it on the replacement control panel from the trunk mount head when substituting it otherwise you will have no speaker audio when you reassemble the radio. The trunk mount radio control head does not have this capacitor installed

XTR Error Codes

Programming XTR Mobile Radios

Programming hardware for an XTR is a Midland 70-1080, 70-1308 programmer, or GCC's clone of the 70-1308 called the XTR1.  You can order it here.  The 70-1308 or XTR1 plugs into your computer's serial port. Beware of using programmers that only use a single MAX232.  These usually derive power from the serial port and do not work 100% reliably on ST2 radios with some computers. To program you just connect the programmer to the programming port and start the software. 

XTR software comes in both MS DOS and Windows versions. The Windows version works with Win95, Win98, 2000 Professional, and XP.  The Windows version is more reliable than the DOS version with newer computers. 

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