MB7UM – 2m APRS Digi
MB7UM is the groups 2m APRS digipeater.
| Location | Madingley | Access Method | Valid Data |
| QTH Locator | JO02af | CTCSS | N/A |
| Input Frequency | 144.800MHz | Timeout | None |
| Output Frequency | 144.800MHz | Reaccess | N/A |
| Mode | 1200bps APRS Digi | Reaccess Period | N/A |
| Polarisation | Vertical | Aerial | Folded Dipole |
| Height AGL | 40m | Direction | Omni |
| Height ASL | 192m | ERP | 25W |
http://www.dcc.rsgb.org/ShowNodes.asp?call=MB7UM
NOTE: MB7UM does not gate traffic to the internet, it only repeaters APRS beacons.
Local APRS/DPRS Map:
Below is a map of all APRS and DPRS stations hear in and around Cambridge.
Most, but not all, will be via MB7PI, MB7UM, MB7OV or GB7PI.
Madingley Site Power Failure
Hi all,
Thanks to everyone for the updates regarding the loss of power at the Madingley site on 20/01/12, it sure gave the batteries a good test and I would say they worked well.
If you look at the telemetry MB7UM sends out here http://goo.gl/C6g7f you can see the 4th graph down showing the mains power state (010 for ON and 000 for OFF). Power went for somewhere between 16:50:41 and 17:02:20 and came back on between 00:00:17 and 00:11:53 (how cool is it we can tell this now!). That was a duration of about 7 hours.
Back on the telemetry, the 24v graph (2nd one down) shows a drop in voltage from ~27.5v to 25.0v, 27.5v is the charging voltage, but held steady at 25.0v for most of the time after, some slight fluctuations towards the end. The 12v (top graph) didn’t change at all (the fluctuations between 13.9v and 14.1v is probably ADC error). Note the graphs are the actual value x10 which allows greater resolution.
The only thing I need to work out is why the temperature jumped 8C when the power can back on (between 00:00 and 00:47). This *might* be an ADC reference voltage error, but I can’t see how as it is run off a 5v rail which shouldn’t have been affected. There is a heater in there so maybe it’s just a very good one!
Anyway great work by Phil G4BIK who not only updated GB3PY’s logic to send a ‘B’ between overs instead of a ‘K’ when on batteries, and for plumbing in the new rectifier and battery backup system which worked a treat over the 7 hours.
Gavin M1BXF
CRG Technical Coordinator
MB7UM Telemetry Added
After some concern about the lack of information about the conditions such as voltages, main status and temperature at the Madingley site, Gavin M1BXF designed a PIC interface which monitors all these parameters and updates MB7UMs APRS beacons accordingly which can be displayed here: http://aprs.fi/telemetry/a/MB7UM?range=month