A Kapadokya Guesthouse Radio That Forgets Winter

Every November I get the same message from a friend who runs six rooms in Ortahisar: “the internet is fine in the courtyard and dead in room 3.” Not the router — we replaced that two years ago. This is the point-to-point link between the office and the annex, a 5 GHz Ubiquiti pair I set up in 2022, and it has failed in exactly the same way for three winters running.

The symptom is boring and specific. Signal drops from -58 dBm to about -79 dBm overnight when the temperature goes below roughly -4 °C. Throughput on the annex side falls from ~80 Mbit/s to under 3, and the booking form starts timing out. It recovers by 11:00 when the sun hits the wall. No log entry, no reboot, no error. The unit just quietly gets worse.

What I did the first winter was wrong: I raised the transmit power on both ends. That made the numbers look better on the dashboard and did nothing for the guests, because the problem was not the radio’s willingness to shout. The second winter I ran a small logger on a Pi in the annex instead of trusting the dashboard’s daily average:

*/5 * * * * /usr/bin/ssh -i /home/pi/.ssh/link \
  ubnt@192.168.77.2 'mca-status' \
  >> /var/log/airlink/$(date +\%Y-\%m).log

mca-status prints the raw counters — signal, noise, ccq, txCapacity, rxCapacity — and grepping two months of that line-by-line showed the pattern clearly: noise floor climbed about 6 dB as the wall cooled, CCQ fell to single digits, and the unit kept reporting “connected.” The dashboards were averaging that away.

The actual fix, eventually, was mechanical. The annex unit was mounted on a cold exterior wall with a short bracket, and the radio was sitting a few centimetres from the masonry. On a hunch I moved it 40 cm out on a longer arm and wrapped the cable joint properly. Noise dropped back to its summer level and the third winter was mostly quiet. I do not have a clean physics story for this — thermal drift in the radio, condensation in the connector, or just multipath off a wall that behaves differently when cold; I genuinely do not know which. What I do know is that the cheap fix (move the box) held and the expensive fix (new radios) would probably not have.

Where this breaks down: the logger only works because the link stays administratively up, so it tells you nothing about a hard outage — for that you need a ping from the far side, which I now run separately. It also assumes you can SSH into the radio, which you cannot if the guesthouse owner has changed the password and forgotten it, as happened once. And none of this helps if the actual complaint is the 2.4 GHz access point inside the annex, which is a different failure with a different signature.

If you run a long outdoor link through a cold season: what does your noise floor do between August and January? Mine moved more than any firmware update ever did, and I would like to know whether that is normal or just this one wall.