Intriguing reception, though probably not a time signal. Three key reasons working against that possible diagnosis:- Not on any ITU or BIH list. While those are not always up to date, time stations don't come and go on a whim, so there would normally be plenty of advance planning and notice.
- Very peculiar frequency. Back when time was computed from solar observations that were used to calibrate mechanical chronometers, it was reasonable to transmit time signals on any frequency the Navy had available. Ships at sea, clock makers, railroad offices, radio stations, and everyday folks would tune in at scheduled times to calibrate their own timepieces on the regularly published frequencies, the exactness of which didn't matter much.
These days, however, because any time signal is invariably generated from highly precise frequency standards, almost nobody would think of not also deriving their carrier (and any modulation frequencies) from relatively simple frequency multiples or sub-multiples of the standard reference. In most cases, this means a multiple or sub-multiple of 5 MHZ, since that is a relatively easy frequency at which to discipline an oscillator against cesium or rubidium sources. Globally allocated standard T&F frequencies therefor tend to be only a single division (2.5 MHz) or harmonic multiple of 5 (10, 15, 20, 25 MHz) at HF. (Only slightly more elaborate synthesis is required for the ±5 kHz allocations, which can still relatively easily be derived. wholly from the reference frequency. Alas, poor CHU has to employ more elaborate synthesis and/or disciplining techniques for their chosen spots.)
At LF and VLF, if a signal makes any pretense of being a time and frequency reference today it needs superb carrier phase stability, at least equal to that of the atomic clock source. This requires as few divider and multiplier stages as possible, and preferably no alternate N/N+1 divisor nonsense to give us the jitters. Any multiple of 20 kHz (20, 40, 60 kHz) is trivially easy, and any whole multiple of 5 kHz is no challenge. Shucks, even 77.5 kHz is not a big strain (155÷2). :)
Could someone transmit a signal for timing purposes only, without caring about its frequency? Sure. But why bother on an unprotected frequency in an inherently noisy band, and why bother when even the cheapest, least sophisticated GPS chip on the market will yield a string of one-per-second pulses at no more cost than a halfway fair LF radio. Which brings us to the final problem with this possibly being a time signal...
- Inadequate information transmitted. A 1 pps modulating signal without a way of distinguishing the start of a minute is next to useless. Some stations omit the 59th second, others extend the starting second, some do both, and a few omit seconds 29 and 59 plus extend Second 0. Where voice is used, stations can also give time of day every minute (CHU, USNO Master Clock) or every five minutes (WWV) or other interval; and every known CW time signal also gives time of day at least once or twice per hour in Morse. But without some way of marking individual minutes, it's pretty much all for naught.
So, if this intriguing and seemingly non-local mystery pulser is not a time signal, what could it be? That's hard to even guess at. Only two thoughts crawl to mind for me (nothing really "springs" up there any more), but maybe these ideas will inspire someone else. First is that old standby, a PLC utilizing a periodic pulse as a keep-alive or "heartbeat" indicator. Second is the possibility of a faulty NDB; perhaps one using an auxiliary transmitter that would normally indicate its status by using the regular ident followed by an "E", but which has a problem of its own and is now sending only the "E" over and over. Pretty low likelihood, admittedly, but who knows?
John