Information on the MX800 Base Station from Spectra Engineering

General Info

Most amps now are wide band, but I've seen a number that do not have the discrete driver transistor. They have a Mitsubishi power module as the first stage and three tuning capacitors. When peeked for maximum power (~60W) they have a 2% bandwidth. As they were tuned for 218 MHz from the factory it's worth retuning for amateur band operation. This will improve the match, which is important when followed with a duplexer.

These 218 MHz amps are not happy doing less than about 25W. Some have displayed spurious emissions when operated out of this 25-50W envelope.

The below was a soft amp. I've found the power out to drop off to less than 50 W (40W normal) at 225 MHz. The MX800 doesn't appear to have a loop power control. Not sure what causes this, but I'll need to test further.

Interfacing

More coming

DCS Decoder

The DCS decoder works, but the CTCSS led doesn't turn on if it's received. The only indication is the M-LEAD which can be configured to be ALARM-1 or M-LEAD. This output is open collector (shorts to ground) when squelch is open and a configured CTCSS or DCS tone is received.

IC18 is the output latch for the LEDs and pin 12 will go high when M-LEAD is active. This is a convenient place to get an active high for DCS/CTCSS active.

MX800-F 220 MHz Technical Brief

Docs

MX800 Technical Manual

Software

MXtools is the software used to manage the radios.

MXtools Revision History.txt

MXtools V3.1.8010

MXtools V3.1.8028 - Needed for >3.6.0 Firmware.

All these need a password to program the radios, and have different access based on the password used.

  'solder' -  basic password, lowest access
  'solderall' - more advanced password
  'solderadv' - more advanced, looks like you can change the model number using this and the channels from narrow/wide
  'solderusa' - not sure
  'solderalllc' - looks to be the best