In October of 2010 I started running a test using a keyer that keyed the transmitter at very slow CW. My dits were 80 seconds long and my dahs were 240 seconds long. Since most of the time I have been using QRSS I normally ran FSKCW at about 6 dits per second. I was always curious about how much farther I could get with lower power if I slowed it down. So, My 80 second test was born. W4HBK's grabber has a very slow 4 hour grabber screen which would be perfect to view my very slow CW on. This Grabber was located in Pensacola, Florida, 1163.7 miles away in Grid Square EM60kj. The test began at the 1mW output power level. I would run for a while at that power level and then reduce it by 3dB or so and then continue until I could no longer detect my signal.
If you compare the color
of the signal trace with the chart in the upper left hand corner
of the grab screen shot
it will give you an idea of the received signal strength at the
W4HBK's grabber station in Pensacola, Fl.
A blowup of the signal portion of the above screen shot clearly showing the "D" and the first "J" of the call before the propagaion faded on the second "J". It takes about 35 minutes to send the letters DJJ at this CW speed. In that time the propagaion on 10,140,000Hz can vary drastically.
I never expected to get to this power level. The truth be known, I never expected to get below about 500 microwatts. The detection at this level was very difficult. I was lucky to get a letter or two. I knew exactly where my signal was located on the grabber because a week before this part of the test I modified my MEPT transmitter's DDS-60 Oscillator and syncronized it to a GPS Disciplined 10Mhz Oscillator to stop any Drift. If you will look at the color of the 65uW traces on the 4 hour screen shot and the received power block up in the left hand corner, you can see that my signal is just barely above the ESP level.
Here is the blowup of the screen shot above to better show the
signal. It was very weak and the code
elements are somewhat distorted. But it is my signal at a power
level of .000065 Watts. For the distance
between my station and W4HBK's Grabber of 1,163.7 miles, this
signal is 17,903,077 Miles per Watt.
My test is about over. I don't think I will be seen at 33microwatts. But I am going to try! If I make it I will post it on the webpage. It has really been an interesting experiment.
My test was completed at the end of November 2010. I never did achieve a copiable signal at any power level lower than 65 microwatts with this setup. I am working on studying on other methods of modulation and detection to see if I can break this power level barrier.