Stray Signals

Ham Talk Live! Episode 89 – Puerto Rico Disaster Communications with Val, NV9L

Good morning;

The main critical issue in any true disaster will be the ability to provide electrical power for our radios. All the things most people consider, such as a generator, or using their batteries, are all finite. They will run out of power at some point.

My philosophy is to NOT USE something that will require an outside power source to recharge or refill our batteries, and that includes getting gasoline, diesel, or propane for a generator. Instead, I suggest using alternative or renewable energy sources, such as photovoltaic solar panels, which are usually available most commonly in the polycrystalline Silicon cell form with 36 cells and going through a charge controller, and also small wind generators. Yes, that is an “and” between the two types. Solar power and wind power are compatible, complementary, and portable. They go together very well to provide a good back-up electrical power system. When we have sunlight, the solar panels will do most of the work. You will get about 10 % of the rated power out of a solar panel in the rain or under clouds. If the batteries begin to drop in voltage when we have rain or clouds, often we will also have wind. Then the small wind generators begin to shine, and they also work well at night when there is wind. At night when the side of the tent begins to flap, and I perk up my ears and hear the whistle of the wind generator blades begin to pick up in sound pitch and volume, I know that the batteries will be feeling better.

For operating a common 100 Watt HF ham radio transceiver, 180 or 200 Watts of solar panel energy will do very nicely to operate a nominal 100 Watt radio that is “rated” to draw 20 or 21 Amperes of DC power at 13.8 Volts. In full normal sunlight, 180 Watts of solar panels will provide just over 10 Amperes of DC current. 200 Watts will be just over 11 Amperes. When talking on Single Side Band (SSB), the average current draw for the radio will be right at about 10 Amperes or only 50 %. The radio needs that 20 Amperes only for the voice peaks for which the battery provides that extra 10 Amperes. For our normal speech, there are pauses and differences in our modulation will vary the current draw for the radio around that 50 % or 10 Ampere average point while transmitting. While you are listening, around 90 % of that 10 Amperes from the solar panels is going to recharge the battery or batteries. CW is about the same as SSB. AM is between 50 to 100 % of the rated current draw depending on modulation, and FM and the digital modes can be considered to require the full 100 % duty cycle, and that is why they ask you to drop your power down to about 25 Watts for long term digital and FM voice conversations.

By the way, this 180 Watt solar power system I described above has been out as far as Herschel Island, latitude 70 North, longitude 139 West, for the 2003 IOTA NA-193 activation that ran for a full week. Trying to get a radio signal OUT of the auroral oval is a real

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