This would be a great experiment for many of the people here. Its not overunity but you can harvest some free energy.
There have been many other devices not to different than this both here and on other forums.
Using inexpensive materials configured and tuned to capture microwave signals, researchers at Duke University's Pratt School of Engineering have designed a power-harvesting device with efficiency similar to that of modern solar panels.
http://revolution-green.com/2013/11/08/wireless-device-converts-lost-energy-electric-power/ (http://revolution-green.com/2013/11/08/wireless-device-converts-lost-energy-electric-power/)
The real challenge is a true broadband receiver or better said a true broadband antenna.
All known antennas and receivers only work in a rather narrow band. And even in this narrow band a very tiny amount of the energy sent out by the transmitter can be harvested.
So, what should be found is an antenna that can receive the electromagnetic waves from a frequency of 1 Hz (ELF = extremly low frequency caused by lightning and other natural phenomena) to 50 Hz (electro smog from the 220 V or 110 V power lines) and finally to 600 GHz (radar) equally well. Such a "true broadband antenna" would suck up all electromagnetic waves present on earth. Still a tiny amount of the energy which is transmitted by all the transmitters, but in sum (over all frequencies) it would be a useful amount of energy.
But it might be impossible to build such a broadband antenna. May be it should be a liquid or gas?
Greetings, Conrad
base collector emissor
but not termed as receiver
but
"magnetic field transistor"
http://worldwide.espacenet.com/publicationDetails/description?CC=DE&NR=19737047A1&KC=A1&FT=D&ND=3&date=19990708&DB=EPODOC&locale=en_EP (http://worldwide.espacenet.com/publicationDetails/description?CC=DE&NR=19737047A1&KC=A1&FT=D&ND=3&date=19990708&DB=EPODOC&locale=en_EP)
+
http://worldwide.espacenet.com/searchResults?compact=false&PN=de&ST=advanced&IN=joshi&locale=en_EP&DB=EPODOC&PA=licentia (http://worldwide.espacenet.com/searchResults?compact=false&PN=de&ST=advanced&IN=joshi&locale=en_EP&DB=EPODOC&PA=licentia)
Sincerely
CdL