Solar Power for Amateur Radio

Powering radio communications equipment using solar energy.

1. Are there any special considerations when using amateur radio gear on solar power?

Yes, there are some issues. Many solar charger controllers actually will generate RF noise when charging. This is most common with pulse width modulated (microprocessor controlled) charge controllers. Sometimes this can be controlled with wire shielding and/or good grounding/DC filtering. RF noise output may vary depending upon battery state of charge (usually less when batteries are near full, depending upon the charger PWM protocol).

2. What are the advantages of solar power for radio communications?

Solar power is ideal for radio communications as the DC power does not introduce line noise or 60 cycle hum. Isolation from the grid (in most installations) also will assure relative immunity from grid power surges. Using solar energy as a power source actually fulfills a prime mission of amateur radio: reliable emergency communications. Solar powered communications will function when everything else is off[line. Solar power can also keep a standby battery bank constantly topped-off and ready to use in the event of a power failure. UPS inverters are also available that switch power over to solar power upon a quarter-cycle failure of the 110VAC grid.

3. What kind of solar panels will be necessary for backpacking, handheld and QRP radios?

A 15W Backpack solar panel is ideal for this purpose. You will get 750 mA in full sun. Use a charge controller and a small 8 AH (amp-hour) or so sealed lead acid battery. Using this setup you’re good for many hours of operation. You can also charge consumer electronic devices as well.

4. What kind of installation will I need to power my home amateur radio station using solar power?

This certainly depends upon the loads you intend to support. Most radio communications needs are used for a limited timeframe daily and the duty cycle (time in transmit) is usually low. Therefore a solar installation with around 200W of panels and 300 to 500 Amp-hours of battery capacity will usually be sufficient (your mileage may vary).

5. Are there any other issues to consider?

Yes, we recommend using Anderson Powerpole connectors for portable operations with the connector installation meeting the ARES standard Anderson setup. In the case of fixed stations, we recommend installing the solar power equipment according to code(UL listed inverter, conduit, load centers, grounding, fusing, load disconnects, wiring, etc; all according to the National Electric Code or NEC).

6. What panels are suited to portable or manpack operation?

Backpack panels that fold into compact sizes and thickness less than an inch. Available in 10.4W, 15.6W, 20.8W and 32W sizes.

7. How about remote base or repeater operations?

You can set you up with the right panel sizing as well as the charge controller, metering and advice on setting your system up for long reliable service. The average amateur or commercial remote base will do fine with between 100 and 300 watts of panels and around 200 to 400AH of batteries. Actual sizing depends upon the duty cycle of use and load sizing. Any remote base needs low voltage disconnect and temperature compensation at a minimum. Good grounding and lightning suppression is also important.

8. How do I power my Yaesu FT-817 using solar power?

Most who use the Yaesy FT-817 with solar power have great results. Run a fused red lead to the positive internal battery lead and run the ground/black lead to the battery negative. Attach a charge controller  to this direct battery jack. Never attach a solar panel to the power input to the standard power input jack as this will likely harm the unit’s charging circuit which (unlike solar charge controllers) is not set up for the full sun voltages generated by solar panels.

9. Can I run a larger amateur radio Field Day station using solar power?

Yes. use 20.8W and 32 watt Nylon enclosed folding solar panels which can charge marine deep cycle batteries. Monitoring battery voltage will tell you how fully charged your battery is or is not (0% charge around 11.5V and 100% charge around 13.4 volts depending upon temperature).

10. What’s the best option for backpackers?

The Nor-Cal ( QRP radios are well suited for backpack operation as they are lightweight and consume very little power. Using a 10 watt Expedition panel and a 2 or 4 Amp-Hour battery and the controller will be lightweight and will permit operation for many hours daily. The controller is lightweight and is a full-function controller.


11. How do I size a system for my 100W radio?

A 100W radio will theoretically draw about 7.5A at 13.2VDC (most small systems have a battery float voltage of 13.2). You will likely only draw 7.5A a fraction of every hour. Most amateur radio equipment is operated 3 to 4 hours a day and during each hour about 1 out of every 3 minutes in transmit.

So, you need to calculate how many amp-hours you intend to draw per day. Let’s say you will run 4 hours a day. Let’s say you will transmit 1 minute of every 3 minutes while operating on average (this is referred to as duty cycle). Your transmitter will draw about 7.5A in transmit and let’s assume 1A in receive. This is typical for many amateur radio transceivers.

So out of 4 hours, that’s 240 minutes; we’ll see 25% transmit (1 minute transmit out of every 4 minutes total) and 75% rcv. That’s 60 total minutes (1 hour) transmit and 3 hours receive.

So this is 1 hour drawing 7.5A or 7.5AH total at 13.2VDC for transmit and it’s 3 hours drawing 1A or 3AH total at 13.2VDC for receive. Add transmit and rcv time together and you have 10.5AH total.

Putting this all together:

1. You need to put 10.5AH back into your system every day given that you will run every day.

2. You have 6 hours of full (peak) sun every day in most areas of the US.

3. So this is 10.5AH divided by 6 hours or 1.75A of solar panel output every day to put your used AH back into your battery bank.

4. Generally we recommend 3 times you daily AH of energy use as your battery backup bank capacity. This is a deep cycle battery bank (car batteries can’t be deep cycled). So this means in your case you want at least 3 X 10.5AH which is about 30AH. 50AH is a common battery size and that would work fine for you.

5. You will need a charge controller in addition. You will also need fusing on the battery lead and a lightning arrestor on the panels along with a good earth ground.


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