I came across a strange signal on 54.25mc while bandwidth testing a 6M antenna, but it turned out that I was hearing a harmonic from 27.125, also known as CH14 on the 11M band. The signal consisted of a steady carrier amplitude modulated by evenly spaced, single frequency bursts (beeps), which decend in audio frequency in steps every few minutes, then the process repeats. After a bit of research I discovered that "Driftnet Radio Buoys" can operate on that frequency, but these transmit an identifier. Other possibilities include Radio Shack pagers and car alarms that transmit a tracking signal. It's got some range to it as these videos show reception over two miles away over hilly terrain. The second video shows the presence of more than one "beacon" with the receiver in SSB mode.. Using a fox hunt process, the signal was tracked to a home in a residential area.