JJY Japan 40 kHz Time Station 1140 UTC 22 Jan 2020

[ChrisSmolinski]

My first time catching this station, fairly weak signal, with a lot of the RFI crud that is characteristic of the modern longwave band.

[NJQA]

Which antenna were you using?

[NJQA]

I’ve got traces of a weak carrier on 40 kHz at 1152Z, but no where near strong enough to ID.

I’m using my KiwiSDR and a 1000 ft LOG.

[ChrisSmolinski]

Which antenna were you using?

This was using the KiwiSDR and 670 ft sky loop. Just checked now, and it seems to be gone, probably too late. I might try again tomorrow morning with a few other antennas.

[NJQA]

I listened again this morning.  You could just tell something was there — without the waterfall it would be unnoticeable.  Strongest fade in was at 1121Z.  I need to try again a little earlier.

Some of the guys in my local ham club have been working JA’s on 160 meters the past few days.  The solar minimum has been helpful for the low bands.
 

[NJQA]

BTW, the magic time for an ID is 15 and 45 minutes after the hour when they send JJY in morse.

It is going to be tough to verify what I am hearing is actually JJY.  On the French and German time stations I was able to get a correct time decode using the Kiwi decoders, so I was confident of what I heard.  This signal is so weak that a decode would not be possible, even if the Kiwi JJY decoder worked (it isn’t operational yet).

[NJQA]

Not a trace of a signal this morning.  What was new was a RFI signal that wasn’t present the previous two mornings.  The VLF spectrum was remarkable quiet until about 0600 local when a wandering RFI signal started up.  It went away for a little while, and then came back.  I suspect a neighbor has a grow light or something...

[ChrisSmolinski]

No luck this morning either. I had a signal on 40 kHz that sounded like it was producing two beeps per second.

[NJQA]

It has been a long time since JJY was on SW but they may have used something like two beeps/second there.

You don’t usually see AM or CW keying on VLF though.  The antenna BW (because they antennas are so short compared to the wavelength) is extremely small and it becomes difficult to build an efficient antenna that has a BW wide enough to support AM modulation.

On-off keying (CW) is also difficult, particularly at power.  I think JJY is a 50 kW station.  Keying a large load on and off is hard on the electrical system and the power supply.  Still, from what I read JJY does send a CW ID, so they apparently do that.  WWVB uses a modulation scheme that raises and lowers power.

Most VLF stations today use a MSK.  It is efficient, has a constant carrier, and works with antennas with narrow bandwidths.  I don’t know what JJY uses but MSK would be my first guess (and I emphasize that I am guessing.)