On Mon, 16 Feb 2009 22:22:20 -0600, Frnak McKenney
wrote:

So any non-loop antenna I can construct will necessarily be a "short
wire" or "electrically small" antenna (two useful search terms).
But how does one go about calculating the impedance of a coat hanger
or an extension cord ("short piece of wire")?

Antennas can be modeled by various NEC based programs. For example:
http://home.ict.nl/~arivoors/
http://www.eznec.com
http://www.nittany-scientific.com

Note that the common "atomic clock" gets its time from WWVB at 60KHz
(about 5000 meters) using a tiny loop antenna. Huge antennas are not
required for many application.
http://www.mas-oy.com/data/MAS_docu_AR.htm
http://www.leapsecond.com/pages/sony-wwvb/

Also, search Google for LOWFER.

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