And now...even lower power!

Well, I couldn't resist the mathematics that said 50 microwatts should multiply up to around 500 microwatts at the beach, the latter being the level my delta loop showed could be heard across the Atlantic.  So off I went last night.

To put 50 microwatts into context, it's less than 1/1000th the power used by a single, typical LED indicator and resistor unit.  In other words, staggeringly low power: 0.00005W.

 

50 milliwatts out into a 30dB attenuator = 50 microwatts(!)

It wasn't the best evening for a test.  After a long period of very quiet geomagnetic conditions, the field was undergoing a moderate disturbance, bringing the auroral oval as far south as the central UK. 

Added to that was an unusual form of what appeared to be lightning, but had no accompanying thunder - possibly a result of being too far away - but rather oddly, also was not detected by lightning monitors anywhere.  This is in fact a culturally-recognised phenomenon, called 'dreigiau' (dragons) in Welsh.  This phenomenon passed quietly down the Irish Sea over a couple of hours. 

Even so, and perhaps even helped along a bit by these phenomena, my 50 microwatts at 14MHz from the usual elevated vertical with two elevated radials first made it to EA8BFK and then, an hour later to WA2TP (a per-Watt distance equivalent of 103,260,000km, or 70% of the Earth-Sun distance!)

Note: due to WSPRlite settings limitations, the reported power is 50 milliwatts, whereas the true output was 50 microwatts with the attenuator fitted.

With up to 9dB 'spare' in the EA8 spot before we reach the -34dB detection limit, this indicates that the lowest practical power that would be detectable from the beach under these geomagnetic conditions is roughly around the 5 microwatt level.

As a further indication of the low power in use, my delta loop and RSP1a SDR at home didn't hear any of the transmissions, despite being only 20km away.

The EA8 spot is coincidental with the start of a geomagnetic disturbance (here depicted as the D (deviation from true North) component), and the WA2 spot with a temporary relaxing of the field.  I've noted an enhancement to EA8 during such disturbances in the past.  It would have been nice to continue longer, but I was quite tired and had things to do the following day.

D-component geomagnetic field plot.  (Tromso Geophysical Observatory)

Forecast auroral oval mid-way between the two 50 microwatt spots. (NOAA)