WSPR Power Levels Newbie problems

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.

It’s like trying to Tune a Piano with a Feather

“Like trying to tune a Piano with a Feather” that was my description of getting a home brew MEPT tuned in the 100Hz segment of the QRP-QRSS sections of the bands.

When Bill of Soldersmoke fame built his MEPT the only RX he had was a very inaccurate solid state rig that drifted. These are some sugestions I made to help him find his TX frequency. The number of new stations coming onto QRSS and the same problem being encoutered prompts me to write this. In addition my memory does not get better, I use my blogs to record things so that if I go away for a few months and forget something I have a reference.

Like most things a good understanding of the Receive side is essential before venturing a signal onto the air. If you can receive other MEPT’s and know their frequencies then you are 99% there.

First the RX needs to be warmed up for quite some time to make sure it has settled.

Here is my Kenwood TS870, a Transceiver I consider to be very accurate and very stable after 5 minutes from switch on the display should read above 070, it will never quite get there it is a few Hertz low but it can be seen to be heading up that way.

Here is my ‘G’ MEPT signal at this time received by the Italy I2NDT Grabber I have just adjusted my TX frequency to 10.140073MHz plus or minus a bit.

So how do we get Spectran or Argo and our RX to display MEPT’s.
First we need to get the received signals in the audio passband of the RX, for convenience 1KHz is a good frequency to choose, it is near the middle of the passband and a round number. No matter what band we are receiving on always use USB (Upper Side Band) and the standard 2.4KHz bandwidth. To produce a 1Khz audible beat note of a particular radio frequency we need to tune 1KHz below its frequency. Hence to receive 10.14000 MHz we need to set our RX dial to 10.13900 MHz.

Next we need to set up Spectran to match.
From the Menu select Mode – Preset QRSS3. The display will now scroll Horizontally.
At the bottom select Show Controls – in the Freq Offset box enter -1000 (minus 1000) as shown.

Now point your mouse to the grey bar between the top and bottom spectrun displays. In the top display is a vertical red line it is reading -150 or more at the red line, Left click the mouse and drag the scale to the left through Zero to place 100(+100) at the red line.
The Right hand vertical grey scale now reads 10 – 20 – 30 up to 100 if it was not hiding at the top. This scale now shows the 100Hz of the 10.140000 to 10.140100 QRSS Band.

When you close Spectran these settings will be saved so you only need to set up once.

If you are new to Spectran do some thinking and tune to the frequency you need to to display WWV on what ever frequency you can hear it on, check the accuracy of your RX dial.

If you are seeing MEPT’s you can put your newly built TX into a Dummy Load and adjust its trimmer to sit your signal where you want in the QRSS band
But beware there will be more than one of you, even with a few mWatts into a screened dummy load you will find it hard to get rid of your signal.

Here I have re-tuned my RX 70Hz higher than 10.13900MHz the signal is some 30dB down but strong, comparison with the Left Hand side of the trace makes it obvious which is the fundamental.

This is where the Feather comment comes in, a tiny adjustment of the trimmer can shift your signal way out of the 100Hz window, you are using a Dummy Load so tweek and twiddle to get used to it, like all things after a time minute adjustments become easy.

When you are fully confident in your skills, settings and accuracy you can put your MEPT on the air. If you are lucky like me, (I2NDT Grabber is almost a certainty during daylight hours) your signal will pop up right on your determined frequency on a Grabber. Alterantively you can get a friend to listen / look for you but beware many Hams do not know within 200 to 300 Hz where they are on the band despite what their dial reads.