It is great to see new licensees building QRP rigs and showing an interest in more than gathering on the Local Repeater swearing and behaving like louts. I have felt for some years now that I can no longer contribute to the local repeater group who provide facilities which bring Amateur Radio into disrepute.
K1JT’s WSPR Weak Signal Propagation Reporter software has enthused many operators both old and new. Several times I have noted that there is misunderstanding from many stations about the software and power level setting. More than once the statement has been made that WSPR is so clever in that you can click a box on the GUI and so set your power output down to mWatts.
Let us get that straight you can’t.
This spurs me on to write a post in simple language for beginners, at least then I know it is available somewhere on the web.
Given the question ‘How does the WSPR software reduce the power of my rig’.
Well it is like advertising, if you can’t work out how it does it, most likely it doesn’t.
How could a computer program alter your radio output unless you have a full CAT control system? Those boxes on the program are Data Input boxes where you tell WSPR what information to send, like you callsign locator and power.
So let us take a look at the output of your FT-450 etc. on USB ‘cranked down to 5 Watts’.
Have you noticed that with the Microphone plugged in if you say nothing into the microphone there is no output, if talk quietly the output is low, if you shout it is 5 Watts. Now there is a clue for adjusting the power output. This is due to the audio producing a variable amplitude (yes AM) drive level which on SSB results in more power out given more audio input
When you run WSPR you are putting 4 audio tones one at a time into you FT-450 etc. from the computer, the audio amplitude level of these tones will control the RF output level of your radio. Just like shouting into the Microphone will over drive and distort your signal, the computer output level can and most likely WILL overdrive the rig.
Note. Windows will change these levels when you run other programs, when you return to WSPR or other Digi Modes you need to set up the correct levels again.
Just like not speaking into the Microphone, turning the computer audio levels to zero will produce NO output from the TX. The correct levels will undoubtedly be very low, both WAVE and OUTPUT/SPEAKER level.
Each time you run WSPR or any Digi Mode set the Windows Audio Volume Controls WAVE and OUTPUT to zero and set up the drive correctly or at least check that they are right.
For Whisper level settings set WSPR to TX, measure the output power of the rig at the antenna socket into a 50 Ohm Load. Advance the Windows Audio WAVE control by one division only, then advance OUTPUT by the smallest amount possible, you should see a measurable amount of RF power out. Set your required level by increasing both WAVE and OUTPUT a little at a time to say, 40mW.
So often I have reported over driving to be told ‘well I have the Windows Audio controls set about half way’. No actual adjustment. It is so frustrating to hear an ex CB guru instructing a newbie ‘just set the controls about half way’.
Never increase the drive level to produce ALC action.If you are setting for a higher power level the correct method is, adjust for ALC indication then back off well below the point where ALC action starts. ALC is distortion like it or not.
Now you can enter your power level value into the WSPR Set Up drop down box and the Data you send will be valid.
I have no doubts that the majority of Hams on WSPR do not measure their output accurately consequently all Data on WSPR.net is invalid in my view.
Personally I have no trouble setting 10mW levels on any of my HF 100 Watt rigs although it does need careful setting.
Finally note that ‘cranking down’ (or up) the indicated front panel power level on the rig does not change the power you have set by the previous careful adjustment. Go on try it.