Those who use the 630m, either as swl's or hams, are familiar with the ever present steady signal in that band at roughly 475.632 khz. It appears as a "stripe" in the waterfall if you're running the wsjtx wspr software program. It doesn't appear that it's just an unmodulated carrier as modulation can be heard riding on it. Anyway, I was monitoring the 630m band today... no stations were being decoded, but I noticed an anomaly in the signal strength in the waterfall of this unidentified station. Usually, the signal doesn't vary much at all but at the time shown in the screenshot, there was a brief strong increase in the signal level of this station. I've been watching/monitoring 630m for a number of years but have never observed this much change in signal stength before.
One wonders if this was a very brief increase in propagation, or if whatever is generating this signal had really boosted it's power level for some reason. Guess it'll just remain a mystery for now.
www.dropbox.com/scl/fi/cm5o9p13ax8xgmd6trfje/enhancement.jpg?rlkey=qdhozus4gg1cu61x1zhfbm1fu&dl=0