Sun Communications William A. Gerosa - N2RSV c. 1992 William A. Gerosa After completing and defending my thesis entitled "The Economic Feasibility of Photovoltaic Implementation", I wanted to step out of the academic circle and get my hands dirty. I wanted to construct an actual system that proved some of the tenets put forth in my writing. I assembled a solar-powered amateur radio communications system. This system allows conversations with friends and family whether they are at home, in the car, by the pool or miles from the tether of a telephone. The best part is that my setup is completely powered by the sun. The system, and its power source, is a one time investment and there is never a "per call" charge. The System The heart of the setup is an Alinco DJ-580T 2 Meter / 70 Centimeter portable transceiver connected to a 35 Watt RF Amplifier made by Communications Concepts. The antenna is a Cushcraft AR-270 quarter wave ground plane mounted on a housetop approximately 40 feet above the ground. Power is supplied by two 10 Watt amorphous silicon panels sold by Pak Rat Electronics. The two amorphous panels charge a Sears (#96522) deep cycle marine battery through an 8 Ampere charge controller (#20-210) sold by Pak Rat Electronics. The battery is capable of holding 115 Ampere-hours. This storage capacity is more than adequate. Power Consumption The Alinco transceiver consumes 95 milliAmperes when squelched, utilizing battery saver mode and waiting for a signal. I leave my system on 16 hours a day so this works out to be: 0.095 Amperes x 16 hours = 1.52 Ampere-hours per day for the receiver. The Alinco draws close to 1.5 Amperes when transmitting at high power. This is close to 4 Watts at just under 12 Volts. I rarely talk for more than one hour in a twenty-four hour period. This would be one-half hour of transmitting assuming a 50/50 ratio of talking to listening. The figures are: 1.5 Amperes x .5 hour = 0.750 Ampere-hours per day for the transmitter. The RF Amplifier does draw some idling current, so I connected a relay with a switch to the microphone's push to talk switch so that the RF amplifier only uses current when the Alinco is transmitting. The amplifier consumes close to 3.5 Amperes and produces 35 Watts of RF output at high power. I rarely use high power, but using this figure puts the system to the test. Using the same half hour figure for transmit time, one day's usage = 3.5 Amperes x .5 hour = 1.75 Ampere-hours per day for the Amplifier. The aggregate power consumption figure comes to 4.02 Ampere-hours per day for the whole radio system. These numbers are somewhat overstated because most of the people I talk to are within thirty miles of my house and I only need about 5 Watts of RF output to contact them. This situation reduces the total power consumption from 4.02 to 2.77 Ampere-hours per day. Power Creation My calculations indicate that on any fairly sunny day each panel produces 0.6 Amperes per hour at 16 to 18 Volts. All measurements were made shortly after the system came online during July and early August, when conditions were ideal. This is the average current and voltage over the four and one-half hour period that the panel receives "full sun." Currents of 25 to 100 milliAmperes at 14 Volts, per panel,are present before and after this period, but are minimal compared to the bulk of the charge occurring between 11 AM and 3:30 PM. For the "bulk" of the charge my calculations are: 0.6 Amperes x 2 panels x 4.5 hours = 5.4 Ampere-hours per day. When the communications system is used under the above parameters on high power we see that there is a surplus. Even when the system is running at high power this gain is 1.38 Ampere-hours. At low power the surplus is 2.63 Ampere-hours. This situation is desirable because we get our share of cloudy days during the winter. Hardware Costs The panels were $54 each including extruded frames. The Sears battery was $74.95. The charge controller was $45. All other accessories such as fuses, connectors and wire amounted to approximately $20. Benefits The generation of power "on site" is becoming increasingly more common. We are seeing a parallel development in the communications industry as cellular telephone cites and satellites play an increasingly larger role in communications. Cellular phones can be charged from the sun. Remote areas can have reliable two way conversations with mainstream society, without the need for large expenditures on stringing power cables and telephone lines over many miles. Photovoltaic power and communications systems are perfect complements because most communications gear demands DC voltage at relatively modest currents. These systems do not require inverters, circumventing that loss. Wire losses can be reduced when the communications equipment is situated near the power generation site. Photovoltaic power generation is absent of electrical noise or ripple voltage often present in standard ac to DC power supplies, a real plus in radio communications. Additions I am working on powering a Commodore 64 computer from the panels in the near future. This computer will act as an "answering machine" for my radio when I am not around the house. It will be an added benefit, but will probably require the addition of one or more panels. Access Author: William A. Gerosa, 405 Tarrytown Rd., Ste 212, White Plains, NY 10607 Alinco Electronics, 438 Amapola Ave., Unit 130, Torrance, CA 90501 Communications Concepts, 508 Millstone Dr., Xenia, OH 45385 Cushcraft Corporation, 48 Perimeter Rd, Manchester, NH 03108 Pak Rat Electronics, POB 690073, Houston, TX 77269