Foxhole Radio Modifications

I played around with the foxhole radio we made earlier to try to increase the signal.  In a traditional foxhole radio a single diode is used, which cuts off half of the AC from the signal and converts it to a useable audio wave.  This is a half wave rectifier, which does not make use of all the power potentially available in the signal.

I used four LEDs hooked together in a diode bridge to make a full wave rectifier where current flowing in both directions in the signal are converted to an audio wave. 

Here is the actual setup.

And a closeup of the LED diode bridge.

Before with the single diode I was able to tune in stations from 10 to 15 miles away.  I was able to find the same stations again, so it is not worse, and I also found three more stations, the tower of one of these is just over 20 miles away!  Below is a map of the station locations I tuned in using this setup (click for a larger image).

So there seems to be some improvement.  I searched for mention of this online and in forums I read that using a full wave rectifier in an unamplified radio wouldn't help because of the voltage loss from the signal going through two diodes instead of just one (these types of radios work with very low power so any loss is bad).  However, my results suggest is does help.  For much beyond 20 miles I am going to run out of island.  I need to bring in signals from over 50 miles away to reach the next island, Moloka'i.  Perhaps next I will try to increase the size of the antenna.