Transmitting 475.726 KHZ WSPR 2.0 mode 24x7 as of Nov. 2014
Do you have a receiver and a modest antenna that will cover just below the broadcast band? See if you can hear my 600 meter beacon transmitter running WSPR digital mode. This is part of the ARRL 600 meter Experimental Program. The beacon operates 24x7 from central Arkansas. You should hear a carrier tone with a little bit of buzz listening with your BFO on. Signal decoding requires a PC with sound card and K1JT's Weak Signal Propagation Reporter software from here.
Scroll down below the map and select LF/VLF band then click the Update button. Clicking on the map zooms in for more detail. My call is WD2XSH/15. Mouse clicks on the red and blue boxes show more info.
SAC NDB transmitter SS-250C set for 20W output.
The SAC is driven by mixing a 3000KHZ fixed signal from an HP-3586B with an Icom-706MKII in USB mode. WSPR 2.0 is the software providing the encoding and control functions.
The antenna is a 1/4 wave end-fed long wire sloper, supported by evergreen towers. The antenna runs north/south axially. The peaks of the antenna are at the 60 foot tree top level. There are two 1/8 wavelength counterpoises that simply lie on the ground.
A simple L-network tuning circuit provides a match from the coaxial output of the transmitter to the end fed wire. RF ground and the two counterpoises are tied to the cold end of the matching circuit inductor.