For the first time in months the mystery signal I discovered was detected on a lower frequency. This time it was heard on 4.934Mhz at 0347 UTC. It was sweeping lower as noted previously, however, doing so at a noticeably slower rate. Below is a histogram analysis recording of it. This is similar to a spectrum analysis, but is in detailed colors. This analysis is interesting because for the first time, I’m hearing what sounds like a low frequency rumbling noise in the transmission. I’ll continue to monitor this for awhile longer to see if this signal will return back to the original frequency range it was first heard in. Again, the usual range I’ve been monitoring this in was between 5398 and 5505Khz and always began around 0400UTC.
Interestingly, to cast any shadow of doubt this may be something local to me, I decided to use the WEB SDR website. I selected a few controllable non-local SDRs, including one from Europe. I was able to hear this signal on each of these. This clearly indicates this signal is not a local generated noise or interference of some type.
UPDATE: At 0400 UTC the signal parked itself on 4912Khz. It stopped very briefly at exactly 0400 UTC, then re-started. I doubled checked that original frequency range I first heard this signal in, (between 5398 and 5505Khz), and it wasn’t heard. At 0405UTC the signal began drifting very slowly until it reached 4909Khz and parked itself there for several minutes. I continued to monitor this signal until 0427UTC. No change was noted at that time.
Is this a new “home” frequency range for this signal as we enter DST? The mystery continues!