In Holice, you may have seen beautiful solar panels at the stock market. There are no limits to invention, so the idea is directly offered: to power the radio station with solar energy, either for portable, mobile or stable operation.
One radio station operated in this way can be seen at Viktor OM3WIK at the cottage under Rysmi at an altitude of 2250 meters.
The efficiency of solar panels has increased a lot with the development. The myth that a solar panel does not produce any current outside of direct sunlight has long been dispelled. In fact, its capacity is around 60% even with indirect solar radiation. Solar panels come in certain dimensions, nominal voltage and of course current. For our purposes, panels with a voltage of 18V and a current from 250mA to 1000mA are the most suitable.
Due to the price of solar panels, those with a lower current are more affordable. A panel with dimensions of approximately 30 x 30 cm is capable of delivering 250mA of current at full irradiance at an open-circuit voltage of about 20V. It is not large, so it can easily be used on a portable device.
The capacity of the solar panel alone would not be sufficient for reliable operation with outputs above 1W of power (it must be remembered that the solar panel may not always be efficiently irradiated). Therefore, we will use it as a source of constant current with which we will charge the batteries of the radio station.
A connection with the L200 circuit, which is cheap and easily available, serves as a source of constant current. Apart from that, we only need a minimum of other parts. Capacitors C1 and C2 are blocking. We determine the amount of current with resistors R1-R4. Their value can be calculated for any current according to the formula R = 0.45/I [ohm; -, A]. For 200mA (optimal charging current for 2Ah cells, resistance is 2.2 ohm). We choose other resistors in such a way that we "squeeze" the last mA from the cell even in indirect lighting and lastly (in dim to dark conditions). So we choose the last resistor for a current of around 25mA, i.e. 18 ohms.
A milliammeter at the output serves as a control. It's a good idea to keep it plugged in and occasionally check for current drops. If so, the solar panel is underlit. The output is connected to the accumulator that powers the radio station (it can be internal, in which case we terminate the cable with the corresponding connector, or external, in which case we terminate the cable as needed, for example with crocodile clips).
The connection is an ideal accessory for a portable QRP prevádzku, či už na KV alebo VHF. Think of the stations that disappeared from the transmitter in an instant because they "ran out of batteries". Their fault! They were supposed to have a solar cell with them and recharge the batteries, HI.