MB7UNE – Magor, Caldicot

MB7UNE is an APRS gateway system running on 144.800MHz. The setup consists of the following :


  • PSU : 13.8v 5A linear
  • Radio : Motorola GM340
  • Time out timer (ToT) : 30 second
  • Forward power at back of radio : 5.56dBW (approx. 3.6 watts)
  • Antenna System gain (antenna gain less coax loss) : 3.43dB
  • Maximum Deviation : +- 2.5KHz
  • Emission code : 8K00G2DCN
  • Max ERP permitted : 9dBW (7.94W)


  • Diamond X300N
  • Gain : 4.35dBd
  • Height : 14m agl
  • Elements : 2 x 5/8th on 2m
  • Max wind : 50m/s or 112mph
  • Length : 2.9m
  • Max Power : 200w
  • Nominal Impedance : 50ohm
  • SWR @ 144.800MHz : 1.4 : 1

Coax Feeder

  • 12m of Ultraflex7 from Messi & Paoloni
  • 0.82 db cable loss for the 12m feeder length (excluding connectors)
  • 6.9db loss for 100m at 144MHz
  • 910watts at 144MHz handling
  • 75pF/m +- 2
  • 83% velocity factor
  • 50ohm nominal +-3
  • Terminated N-Type both ends (n-type to bnc adaptor at radio)

EMF Compliance

Compliance based on maximum power output defined by the NoV. Details Here


MB7UNE uses a WX3in1 Plus 2 from MicroSat. It provides the following features :

  • Digipeating – receiving of APRS RF packets, decoding and if valid will repeat them out if required. The hop count is used in this decision, and decremented if the packet is digipeated. A trace is also added. The packet will be dropped if a number of checks fail.
  • iGate – will take APRS-IS gateway packets and will send them out over RF. There are a number of conditions required for this to happen, such as if a station is local and has it been heard in the last 30 minutes. There are also a number of filters that prevent RF ‘flood’.  MB7UNE will also inject APRS packets heard via RF into the APRS-IS internet system.
  • Monitoring – temperature and psu voltage are included in the position aprs packet, sent out every 15 mins or so. This temperature sensor is attached to the back of the WX3in1 and as such is shack temp, not outside temp.

If the are any issues please contact me via [mb7une <at> grange-lane.co.uk]