Sunshine QSO
The Sojourner
While this "batteryless power" thread made for fascinating reading, it appeared to be more academic than practical. But the more I read, the more interested I became. Then one day I began to think about solar power Like many QRPers, I have used solar panels to charge batteries, but it was always the batteries that powered the rig, never the panel. So I set a goal to make at least one contact using a solar panel, by itself, as a power source for a QRP transceiver. I was hooked.
Several years ago I bought a solar panel from a surplus electronics mail order company in Arizona. The panel is quite small and measures 12 inches long and 6 inches wide. It was originally designed to power roadside emergency telephones. I hauled it off a shelf and began running some tests.
In bright sunlight the little solar panel produced almost 21 volts at 130 mA but I quickly learned that it didn't take much of a load to drop the voltage significantly. If this experiment were to succeed I would need to come up with a very low power transceiver.
Looking through my arsenal of QRP rigs I spied my scratch built NorCal 40-9er. I hooked it up to a variable power supply and charted the current versus voltage requirements. At 9 volts it drew 110 mA, key down. At 12 volts the current increased to 140 mA. Power output ranged from 320 to 500 mW depending upon the input voltage. The 40-9er was a good match for my solar panel.
Before I could connect the solar panel directly to the transceiver I had to build a voltage regulator. The panel's unloaded output voltage was much too high for the 40-9er. A 7812, 3terminal voltage regulator, two capacitors and a piece of Radio Shack perfboard took care of the over-voltage problem. With the regulator in place the output voltage never exceeded 12.1 volts regardless of how bright the sun was.
The big test came on a sunny Saturday afternoon. I set up a rickety old card table in my back yard and covered it with a checkered tablecloth. The 40-9er, headphones and hand key were placed up on one side of the table and the solar panel and voltage regulator on the other. The panel was oriented directly toward the sun and a quick voltage check confirmed that the regulator was working. I flipped the 40-9er power switch to ON and was greeted by a burst of summer static and a couple signals. It was show time.
It took several CQs to finally make a contact. I was ecstatic when I finally heard Clark, WA3JPG in Irvine, California calling me. Clark gave me a 569 report and copied my 400 mW signal just fine throughout our eighteen minute QSO.
A couple hours later I called CQ again. This time I received a call from Mahlon, WA7ZBL in Bend, Oregon. Conditions were not quite as good as before but we managed a fifteen minute contact despite heavy QSB and an abundance of QRM. Later that afternoon I checked the great circle distance between my central California QTH and Bend, Oregon on qrp-l. My 400 mW solar powered transmitter spanned a distance of 517 miles thereby qualifying Mahlon and myself for a 1,000 Miles per Watt award. At that point I labeled my solar powered experiment a complete success.
While this may have begun as a "just for fun" project, it quickly turned educational. I discovered many new things about energy conservation and power management along the way. It has also changed the way I think about low power operation and QRP rigs in general.
Educational or not, there will be many more "Sunshine QSOs" at KD7S. This is way too much fun to do just once. Want to join me?
*****
Bill Jones, KD7S, a contributing technical editor for The ARS Sojourner, is an expert builder, QRP operator and outdoorsman living in Sanger, CA.