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Thursday, August 6, 2009

Micro-watt WSPRing by Gene, W3PM

Hi Bill,

As you know by your experience using 20 milliwatts, Weak Signal Propagation Reporting (WSPR) is an excellent mode to experiment with low power. A QRPp experimenter can received near instantaneous automated reports over the internet from hundreds of stations throughout the globe.

During the last few days, I have been experimenting on 30 meters with output powers as low as 20 microwatts. No one has spotted my 0.00002 watt signal yet, but K8CXM has spotted my 50 microwatt signal at a distance of 553 KM at 2332UTC, 05 AUG 09.

I used a 100 mW GPS timed beacon with a step attenuator to an indoor doublet for all the tests. All equipment is homebrew and the output power is verified with a HP-432A Power Meter. If you look in the WSPR on-line database the power is reported as 0.100 watt because it was too difficult to pull out and reprogram the beacon’s PIC controller chip for each change of power. In any case, there are no provisions to report power levels below 1 milliwatt to the WSPR database.

Other noteworthy spots:
100 uW - K8CXM, 2252UTC, 05 AUG 09, 553 KM
200 uW - AI4SA, 0530 UTC, 02 AUG 09, 333 KM
500 uW - NJ0U, multiple spots 31 JUL & 01 AUG 09, 716 KM
500 uW - K1JT, 1440 UTC, 31 JUL 09, 1215 KM
500 uW - W3HH, 1240 UTC, 31 JUL 09, 764 KM
5 mW - VK6DI, 2232 UTC, 05 DEC 08, 17,858 KM

A 6.5 meter auto tuned vertical with 50 ground radials was used for the VK6DI report. The vertical is disguised as a birdhouse support because I live in an antenna restricted neighborhood.

Of course all the credit goes to the receiving stations that no doubt live in a very quiet RF environment. The reports do not represent any records, but they may be of interest to other QRPp experimenters. .

Gene W3PM

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