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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 CTSolar 10.4W 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. CTSolar produces just such a powerpack that will run your amateur radio as well as consumer electronics needs. This unit features low-voltage disconnect to protect your battery as well as state-of-charge indicators to help you judge battery capacity. We also market a 3A lithium battery pack in 6AH and 12AH capacity. This unit is incredibly lightweight and versitile.

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. Do you have any products suited to portable or manpack operation?

Yes, we sell durable lightweight folding panels housed in a zipper rip-stop nylon case. These backpack panels fold into compact sizes and thickness less than an inch. Available in 10.4W, 15.6W, 20.8W and 32W sizes. Our laminate construction makes these panels very sturdy without many of the problems with glass laminated modules. Drop this panel into your backpack and you're good to go. Our backpack panels also feature grommets in their corners to permit temporary mounting to trees or even a backpack so the panel will charge or provide power while on the move.

7. How about remote base or repeater operations?

We 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. We manufacture turnkey aluminum mounts for panel capacities of 36W, 72W, 108W, 144W, 216W and larger side of pole or top of pole mounts. We also manufacture building roof mounts. The panels we use are ruggedized (no glass). We can also provide custom antenna mounting brackets on top of the solar mounts and a platform beneath the panels for a large 32X32X32 inch Pelican Case for the solar power and repeater components. Larger components can be housed in a ventilated aluminum enclosure.

8. How do I power my Elecraft K1 or K2 using solar power?

Most who use the K1 or K2 with solar power install a power jack on the unused Xverter hole in the back panel. 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 (SunGuard4 available from CTSolar is ideal here) 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. We also sell 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). Our aluminum-framed ruggedized solar panels are also ideal for this application and come complete with a tripod mount. Rapidly deployed and conveniently stored.

10. What's the best option for backpackers?

The Nor-Cal (www.redhotradio.com) 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 SunGuard4 controller will be lightweight and will permit operation for many hours daily. The SunGuard4 is lightweigh and is a full-function controller. The entire setup will weigh less than 5 pounds depending upon the size of battery you choose. We also market a solar charged lithium battery pack. 3A charge current and 3A load with low voltage disconnect and LED voltage status display. 6AH and 12AH versions available.

11. Do you manufacture ARES command trailers:

Yes, CTSolar custom manufactures full-sized and smaller solar powered trailers. From 500W to 5KW of panel capacity. A full battery bank and state-of-the-art charging system and inverters. Light bars and optional propane backup generators also available. We can also solarize trailers for built-in communications command post functions. Internal lighting and DC as well as AC outlets also provided. Call us for details.

12. Can I install a solar power system myself?

Yes. CTSolar can sell you all the correct components and ship them to you. You then just install and wire/test the system yourself. We can assist you in assuring that you have the correct panel and battery bank capacities. You also will need to be sure that your system is installed according to code and you should have a licensed electrician sign off on the installation prior to completion.

13. 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.