On Fri, 17 Aug 2012 12:56:55 +0000 (UTC), David
wrote:

http://w5big.com/spectrogram.htm

Free, made for ham radio, and possibly better:
http://www.qsl.net/dl4yhf/spectra1.html
http://www.weaksignals.com

When using detected audio to compare antennas, make sure you're
comparing signals, not comparing noise levels. Picking up more
atmospheric noise is not the mark of a better antenna.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558