Yesterday, Rich K5RWG and I were able to maintain a VarAC connection on 12m (24.9 MHz) for over 11 hours. We started on 10m around 21:00 UTC and given the geomagnetic unrest, the band was not that good. So, I suggested we hop to 12m where the lower f0F2 (vertical MUF) of the path may enable a more stable connection. We had used 12m before during band hopping sessions and otherwise. On "normal days" 10m was usually better than 12m at the given time.
Starting just after 21:00 UTC, propagation soon became quite stable and good. After we chatted for a while, we left the Verbose SNR exchange going. I expected the path to last at least a few hours. At 06:30 UTC (19th June) I thought the band would close. It did not. I checked the solar x-ray flux and indeed there had been a solar flare at 06:30 UTC, strong enough to cause some D-layer absorption which was nicely captured in our SNR graphs. Once this was over, the SNRs returned back to higher numbers following a rather slow decline. Propagation finally ended just after 08:00 UTC. We had the longest ever VarAC link yesterday. Surely a day of good propagation on 12m but also an indication of the robustness of long-distance VarAC/Vara-HF links.
Note, that my local SNR measurements are affected by suburban man-made noise whereas Rich is in a more rural area of Texas. Hence, my measured SNR values are usually between 5 and 10 dB worse than Richard's. Man-made noise is of course not constant but instead, it varies over time. Both our TX power levels are very similar at around 50W.
Path reciprocity does not require that both sides use identical antennas, but in our case we both have 3-element Yagi antennas at decent height levels.
This is awsome. I shared it on the facebook group !