Go to the WSPR Database to see what is possible with very low power with WSPR.
First choose the band of interest.
Then select sort by: Power
Reverse the order to find the low power spots.
You can see more than 50 spots. Maximum number of spots is 20000. hi.
The lowest power value that can be uploaded to the Weak Signal Propagation Reporter Network
is 1 milliwatt, which is 0 dBm.
Please ignore all the spots with less than 1 mW.
Results with 1 milliwatt
The table below shows spots for 1 mW. (+0 dBm) The short table below shows spots that were made with the 1 milliwatt. The signals have traveled a considerable distance.
In this table all the received signals are "solid copy", since all the signals are received with a SNR of -29 dB or more. The higher the SNR, the stronger the signal.
In one of the spots Joe, K1JT is received with a SNR of +11 dB. (Horizontal arrow)
This is 40 dB above the threshold for solid copy in WSPR of -29 dB. The signal could still be received if Joe had used a 40 dB lower power. Thus with 0.1 microWatt. hi
For more info on this calculation, please click on: Calculated lowest possible power in a WSPR spot.
WSPR with 1 milliwatt can be compared with CW with 12 to 30 milliwatt
or SSB with 100 to 400 milliwatt.