The strongest signal is that at
16KHz but, tuning upwards in frequency, I found the 60KHz signal
used for radio clocks. With all the hash, burbling noises and
buzz saws you must listen out for clean, steady carriers carrying
identifiable modulation or having regular pulsing to identify
proper radio transmissions although some of the weird noises
may well be emanating from aerials because the ELF and VLF bands
are used for communicating with submariners and providing direction-finding
Results can be very variable and, to
hear signals most cleanly, I set my microphone input to maximum
volume and used the maximum boost of +30dB then selected the
best sampling rate of 192,000Hz (Studio Quality) which lets me
tune to about 96KHz. At this setting and with the software AF
gain at -6dB, selecting L (I'm using the left channel for my
aerial), the amplitude of the transmission is indicated as -40dB.
The audio level baseline is -80dB with a 600Hz tone rising to
about -50dB. The mode setting is CW, the tuning cursor carrier
reads 60,390Hz and the VFO 59,640 Hz. There are loads of signals
across the band but I guess many are just squeals and groans
from local equipment, lighting, and other stuff. I'll investigate
later maybe... below is a list of what I could hear. I wonder
if there are any low frequency crystals in my computer, radio
clocks, telephones, printer etc etc ? For example most digital
watches and clocks use 32.768KHz.
Don't pay too much attention
to the frequency I've entered as my tuning was only approximate.
To identify some signals I might connect a small pickup coil
to the Mic input and investigate some items around here...
Later, around midnight rather
than daylight when propagation is different I checked and found
at least some of the wobbly carriers may have been teletype and
a weak carrier about 64.4KHz had 1 second pulses present.