As a follow up to our expedition to Vassfjellet last week, we are back with a status update on the beacons LA2SIX and LA2SHF.
Last week we wrote that LA2SIX was transmitting “dit-dit-dit-dit” on repeat, rather than the expected beacon sequence. The culprit turns out to be faulty switches, which are used to configure standby and test modes for the beacon. Closer inspection of the switches revealed a 2 Ohm on-resistance, and 200 Ohm in off-resistance. In the lab this was sufficient for the onboard microcontroller to discern between a “0” and “1” I/O state. However, in a more RF-rich environment, such as Vassfjellet, this causes bouncing of inputs. Code that is set to enable and disable the beacon based on one of these inputs, is bound to lead to an unhappy beacon.
For now, LA2SIX has been remedied by disabling the buttons in firmware, which puts the beacon in an “always on” mode.
Some tabular facts, a recording of the beacon on air, and a spectrum view of the morse sequence can be found below. If you hear the beacon we would love to hear about it. We appreciate reports on DX clusters, or you can contact us directly.
|50.488 MHz||~25 W||Diplexed with LA2VHF/4||Linear (vertical)|
As for LA2SHF, things did not turn out so nicely. After some dialogue with the troubled radio user, we concocted a number of potential remedies for the interference issue. Firstly we employed antenna nulling in the direction of the affected user, which yielded around 15 dB attenuation. Further, we installed a metal plate between the beacon antenna and the affected user, giving another 10 dB.
Unfortunately the user was still affected by our signal. Since the user has a primary frequency allocation, and 23 cm ham radio is a secondary allocation in Norway – this means that we must cease transmissions. Therefore, LA2SHF will be QRT for the foreseeable future. If the situation changes, or we find another suitable location we might work to bring the beacon back on the air.
For now, we are very satisfied to have deployed LA2SIX, and that all the other beacons are still in service. With the WiFi link also working, we are excited to see what projects we can work from Vassfjellet in the future.