I’ve been hearing this strange signal for several months now. It can be found between 5.404Mhz and 5.495Mhz. It is heard best in LSB or USB modes. It will slowly slide down in frequency until it stops around 5.404 Mhz. or there about, then it will begin to slide back up in frequency until it reaches 5.495 or there about and stops before sliding back down again. This process repeats, but I have noticed that the frequency range can vary. This signal is non-existent during the daytime hours, and seems to begin around 11pm ET or 0400 UTC. It moves right through the European VOLMET station on 5.450 Mhz. If anyone has any ideas on what this may be, please contact me or leave a comment here. It seems to be sampling this band range. I can usually identify many strange signals on the HF bands, but this one is very unusual. What is nice about this particular recording is the signal stops abruptly towards the end of the recording session. I can receive this signal on all of my receivers, including my ham transceivers and with using all of my antennas, loops, long wires and dipoles, etc. It is strongest on my long wire and dipole antennas. Very strange stuff indeed.