[TowerTalk] URI magic antennas

[Jim Lux]

At 08:59 AM 6/8/2004 -0700, you wrote:

>What about supeconducting loading coils and/or elements?  One could
>generate VERY high currents with low losses (unless you count the
>energy requirement of keeping an RF-transparent thermos of liquid
>helium full.)  Just the sort of thing a University Physics lab could
>do.
>
>Let's submerge our screwdriver mobile antennas in a cryogenic
>container.  An additional advantage would be that no bugs would nest
>in there!
>
>73,
>
>   George T. Daughters, K6GT
reducing the loss in the coil will make the bandwidth narrower.  You run 
into this when you contemplate making high efficiency compact loops.  Sure, 
I can get the efficiency up real high with a suitable design on a 1m 
diameter loop on 80m, but it will have to be on 80m, and real slow CW, 
because the bandwidth starts getting down to the 10's of Hz range (at least 
you won't have key clicks!)

There's a whole literature (Harrington and Chu is the usual reference) on 
fundamental limits of bandwidth, physical size, etc. for resonant antennas.