DIY FM Radio running off solar power

[willbanks]

Hello, I finished a schematic for an FM Radio that runs off of a 12V, 6W solar panel. Something like this https://goo.gl/TNsBNG

How would I go about figuring out the maximum distance that the antenna would be able to pick up? Is there a way to boost the distance without increasing the length of the antenna?

[Richard Crowley]

By "FM" do we assume you are talking about the broadcast radio (88-108MHz in North America)?

The distance or "range" of reception at those higher frequencies is rather dependent on the efficiency of the antenna.
A random length of wire will not be as efficient as a dipole or a directional antenna like a Yagi or a log-periodic, etc.
It is also affected by the sensitivity of your receiver, which you can increase with extra RF gain at the input.  And, of course it also depends on the radiating power and distance of the radio transmitters.

And even a simple piece of wire (or a "whip" antenna) will have better efficiency when the length is adjusted according to the frequency of interest.  For example 1/4 wavelength is a popular length.  For example the wavelength of 100 MHz is 3m.  So 1/4 wavelength would be 750cm.

Is this intended for portable use?  or for fixed installation (where you could deploy a more efficient antenna)?

[willbanks]

yes north american. its gonna be used for portable use. so is the efficiency of the antenna based off of how good it actually is or the circuit itself?

(also, this project is more for fun so I can learn more about electronics so the quality of the output doesnt have to be super good)

[Red Squirrel]

As far as power goes not much depends on that as far as a receiver.  It's the transmitter doing all of the work, power wise.  But as mentioned the antenna's design can dictate range, along with other things such as how high you mount it or if there's any pre amp, which I suppose would use a bit of extra power.  Suppose a good tuner MAY use more power than a less good one but probably negligible. 

For a solar setup I would look at a car radio as it's already made to run on 12v and it will have a decent tuner.  Easy to find 12v stuff as far as solar goes.  Small charge controllers, batteries, etc.   I would try to aim for like 30w solar though, 6w is kinda low, as you won't always get that rating.  That rating is pretty much perfect conditions.