A look at the radio spectrum in one image

[SilverShadow]

[Alfie]

More detailed one at http://www.icta.mu/images/spectrum.jpg

[m0lsx]

VLF is 3 to 30 khz, but ULF exists below 3 khz.
I listen down into the Hz & it is possible to use audio equipment to send transmissions through the ground for several Km (5 to 10) using stakes instead of speakers & a form of very very slow morse code that can take hours to send, it is called QRSS.
On ULF I use a variety of equipment, I have a small handheld unit that will hear lightning & the resonance of insects wings among other things, a bat audio detector, a ULF transverter & a sound card system.

[Mark5R]

That is all very intersting stuff alan at the moment I listen all day from above 25 Mhz as my scanners can scan that with squelch off and hear local and nearby users. HF I find interesting but can only use it when I have the time as it needs attention and tuning about where the scanners for above 25 Mhz are going off all day.

I am very interested though in all the stuff that you cant just pick up on an analogue scanner. I use dsd with good results which has enhanced my listening but would like to do more monitoring of other areas like pages and vlf ulf which I have no clue about. I was talking to my mate who came round the other day and he was interested in my scanners. He was talking about submarines and how they have massive antennas and bounce signals and I think he said they were vlf or ulf lf frequencies?

[m0lsx]

Yes the submarines are on VLF, but it is the land based stations that use the massive antennas, but even these are only a fraction of a wavelength. The reason VLF is used is because a submarine does not need to surface to receive it as VLF penetrates water..
The South Pole station operated by Stanford University has a antenna that is around 4 miles long & a few feet above the ice & despite this it still only achieves a 10% efficiency, I forget it's actual power levels, but a 100 watt TX would only produce about 10 watts erp due to the short antenna.

http://vlf.stanford.edu/vlfdata/index.php