WSPR with 5 watts

From time to time I visit the WSPR database to look for interesting spots that are made with very low power.
But this time I was wondering, if there are many operators, that use much more than 5 watts.

To my surprise only a few operators used 10 to 1000 watts.


The WSPR spots are collected on 10 meters in 24 hours.

I chose 24 hours to include all operators, that skip from band to band, following the changes in propagation, in all the parts of the world.

The interval lasted from 9:02 utc on the 20^th of February to 9:00 utc on the 21^st.

The choice for the band was not made consciously.
I selected the 10 meter band, because in the days before, I made an analysis of spots on 10 meters.

Power categories
The table shows the number of spots that were made in each power category from
1 mW to 5000 mW  (5 W) (QRP)
and the number of spots that were made with 10 to 1000 watts.

Results
In the power categories from 1 milliwatt to 5 watts, most spots were made in the category of 5 watts.
This is 42 % of all spots.
I am pleased to see that many operators use  200 mW*  or  500 mW.
200 mW in 15% of all spots and 500 mW in 16% of all spots.
It's good to see that only a few operators use 10 W to 1000 W.  (See also "one kW")

One kW
Not all spots that show up in the database with 1000 W, are actually made with 1000 W.
In the past I have seen WSPR spots from an operator that used a homebrew QRP rig, that he proudly showed on QRZ. But the setting in his WSPR program was wrong. He discovered the mistake.
Later the spots showed a power of 2 watts in stead of 1000 watts. hi.

* Did you know that 200 mW in WSPR can be compared with 4 Watts in CW and 80 Watts in SSB.
    So with 200 mW in WSPR you can see where you 4 watt CW signal could be heard. hi.

G4ILO Whispering with 20 mW and 1 mW

This is an other analysis of the data collected from the
WSPR database for spots of Julian G4ILO.

Julian transmitted with a power of 1 mW and 20 mW.

The table shows, that the spots that were made with 1 mW, 

were about 10 dB weaker than the spots made with 20 mW

The table shows a selection stations that received spots made with both 20 mW and 1 mW

To compare spots over different distances, I use the 

Calculated electrical field strength, E, in microVolt per meter.

For details see the WSPR Propagation Analysis page of this Blog.

The lower the electrical field strength the better the propagation.

A power ratio of 10 means 10 dB. 

Please notice the the value for E is given in Volt/m, so a Voltage ratio of 10 means 20 dB. 

Which is indicated at the top of the table.

A Voltage ratio of 10 is a ratio of 100 in power.

The table shows stations that received the signals, that were transmitted with 1 mW and 20 mW.

Notice the difference in field strength in spots made with 1 mW or 20 mW.

The difference in field strength between the spots of 1 mW and 20 mW is about two steps in this table.
This is about 10 dB.

This is no surprise because, the difference in power between 1 mW and 20 mW 

is  10 log (20 / 1) = 13 dB.

The differences in propagation are huge. 

The field strength of the spots made with 20 mW, received by ON7KO over 600 km, 

show a value of 0,3 microV/m to 0,03 microVolt/m. 

The ratio in voltage is 10 and the ratio in power is 100, which is 20 dB. Wow. 

WSPR with 200 mW down to 1 mW by Hajo DL1SDZ

More and more operators discover the use of very low power with WSPR.
On his blog Hajo DL1SDZ reports of spots, made with 200 mW down to 1 mW.
Hajo reduced the power from day to day, as shown in the second analysis.

The first analysis shows the calculated lowest possible power.
The lowest possible power is calculated from the power sent and the SNR.
The lower the lowest possible power, the better the propagation.

Click to enlarge

The analysis below shows electrical field strength.
In this calculation the distance is also included.
The lower the field strength, the better the propagation.

Click to enlarge

In the analysis all spot over 400 km and more are in cluded.
Thanks Hajo, for the interesting experiment.

G4ILO Whispering with 20mW and 1 mW

Julian G4ILO did an interesting experiment with WSPR. 
He used a power of 20 mW and 1 mW and was heard over large distances.
I made a table of the spots with both 1 mW and 20 mW.
I left out the few spots that were made with 50 mW.

The table below shows an interesting phenomena.
When 20 mW is used, the  calculated lowest possible power is 20 mW or less.
When 1 mW is used the calculated possible power is 1 mW or less.

The Lowest Possible Power is calculated from the used power and the SNR.

The SNR for a solid copy with WSPR is -29 dB.
When a signal is received with a SNR of -19 dB, this signal is 10 dB stronger, 
so the power could be 10 dB reduced and still be solid copy, but then with a SNR of -29 dB.
The Lowest Possible Power is 20/10 = 2 mW 
22 Spots were made with a Lowest Possible Power of 2 mW.

The tables below show the distance, the receiving station and the power that was used.

WSPR with 1 milliwatt

WSPR Database                                                         Click: http://wsprnet.org/olddb 

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.