Power with WSPR

WSPR vs CW 13 dB

How much power should be used with WSPR?
WSPR is a beacon system. The WSPR data can be used to probe radio frequency propagation conditions.  
WSPR uses a low transmission speed.
The lower the transmission speed, the lower the power, that is needed. 

As you will see:  Please WSPR  with QRP.

Roger G3XBM asked Joe Tailor K1JT about the difference between "CW by ear" and WSPR.
Roger placed Joe's response in an entry
on his Blog:
WSPR versus CW - what's the improvement
Click to go to the article.

In a description on the WSJT web site, Joe gives a comparison between WSPR and CW by ear. 

For "CW by ear" Joe gives a SNR of -18 dB for a very skilled human CW opererator.

Joe gives a value of -29 dB for the SNR for a WSPR signal.

So the difference is 11 dB, but Joe estimates that for most operators, the SNR has to be even 15 dB. 

I estimate that the difference between WSPR and "CW by ear"  is about 13 dB for contest CW operators and 15 dB for most operators.

For an advantage of 13 dB, a power of 5 Watts in WSPR, can be compared with 100 W in CW.

So the power in WSPR can be 1/20th of the power in CW.

The value of 13 dB is guideline to estimate the power that you should use in WSPR to approach the situation that you use with CW. 

For an advantage of 15 dB a power of 5 Watts in WSPR, can be compared with 150 W in CW.

So the power in WSPR can be 1/30th of the power in CW.

Calculating with power, 15 dB corresponds to a factor 30,
13 dB is 20x, and 11 dB is 12.5x
Calculating with voltage, 15 dB corresponds to a factor 5.5,
13 dB is 4.5x and 11 dB is only 3.3x

I made a table below to compare WSPR with "CW by ear".

The table shows the values for 15 dB, 13 dB and 11 dB. So you can choose the value yourself.

Please note that a difference of 2 dB or 4 dB is very small compared to the large daily fluctuations (in dB) caused by the propagation.

I very much like the table of 13 dB. (20x)   I estimate that the value of 13 dB, is the value for the skilled CW contest operators. The values are easy to remember, since 100 W in CW can be compared with 5 W in WSPR. So when you use WSPR, please reduce your power to 1/20th of the power that you sue in CW.

If you want to analyse what is possible with QRP in CW, you can use 200 mW (23 dB) with WSPR.
This can be compared with 4 W in CW.

As a low power enthusiast I often use the lowest possible power in CW contest QSO's.
I often use less than 1 W. To analyse the possibilities with 1 W in CW, you should use a
power of 50 mW (17 dB) or less. hi

Please note that WSPR with 100 W can be compared with 3000 W, 2000 W or 1250 W in CW.

So gentleman, please:
                 Think in  dB,  and  WSPR  with   QRP.  hi.