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Solar powered low power radio, part four - final fall fail

Solar panels and new antenna
See part one of this series here:
Quick and simple FM radio station goes solar
See part two of this series here:
Solar powered low power radio, part two
See part three of this series here:
Solar powered low power radio, part three - more mistakes
     In part three of this series I had retreated back to the Scosche transmitter powered by two solar panels and a five amp hour deep cycle 12 Volt battery.
     Digging around in my transmitter inventory, I pulled out an old 2004 edition of the EDM Designs 10 milliwatt PLL FM transmitter.
     I also dug out a 2009 version of a Comet antenna knock off to help that 10 milliwatts get out a little better.
     After re-crafting the transmitter enclosure and mounting the new antenna, I was ready to try again.
     The result - very encouraging!
     Range was far greater, with my signal strong for several blocks. Power was lasting through the night even thought the fall days were getting shorter.
Transmitter, voltage manager and MP3 player
     They say night falls quickly in the tropics, but on the Canadian border our twilight lingers. Up here, the sun slips far to the south as fall turns to winter. The arc the sun travels gets lower and shorter week by the week.
     Not only do the days get much shorter, but the shallow angle of the low sun means the the sun's rays must pass through exponentially more atmosphere to reach us.
     In mid-November, the station was no longer able to collect enough solar power to adequately charge the battery for overnight operation.
     As we approached the winter equinox, the station only operated for a few hours between 1:00 pm and 4:00 pm. On heavily overcast days, the station didn't broadcast at all.
     Adding two more 10 watt panels helped a little, but these short, overcast winter days just don't deliver any meaningful solar energy.
     With 40 watts of solar panels unable to do more than power the station an hour or two each day, the situation looked pretty grim.
     The short, wet days and long dark nights meant the ad hoc, hook-it-up-and-see-what-happens approach was no longer an option. I would need to use a different approach to continue to explore this concept.
     What would be next for solar powered low power radio? Watch this space for more!      


end80 said...

I think your biggest problem is your battery. Get a regular deep cycle 12v car/RV/boat battery from WalMart or somewhere.. You should be able to find a lower priced one for around $100, maybe less. My own test with solar powered AM transmitting had continued for weeks and would have gone for longer if I hadn't of disassembled the setup (it was on my boat). I don't think that little battery you're using has enough time recovery capability.

Low Power Radio Guy said...

Thank you very much for your comment! Yes, battery capacity and recovery time is definitely an important issue, one I will need to upgrade for the next ver. Spoiler alert - In getting some data together for my next post on this topic, there was also a revolting development when measuring solar panel output during the low sun angel winter months - 80% drop in power... more to come!

Low Power Radio Guy said...

P.S., Love to hear more about your AM solar effort - sounds very interesting... on a boat!