On Tue, 13 May 2014 11:44:57 +1000, Clifford Heath
wrote:

On 10/05/14 11:21, Jeff Liebermann wrote:
On Sat, 10 May 2014 09:44:44 +1000, Clifford Heath
Again, the problem is matching the impedance of the shortened antenna.
The losses are not in the antenna. They're in the matching circuit.
wavelengths gain(db) VSWR
(50ohms)
0.250 5.19 1.74:1
0.125 4.85 158:1
0.050 4.75 5954:1
I'm curious how you calculate these values?
4NEC2 does the number crunching for me. I would hate to do the
calculations by hand or with a calculator. I'm not even sure that I
could do them.

Thanks. I'll have to get a version that works for me (on Mac).

I was curious that the VSWR seems to go roughly as the inverse third
power of length, which made it seem like a simple formula could
approximate it.

Clifford Heath.

First of all, you need to kill the reactive impedance, for a short
antenna with a suitable inductance.

Secondly, you need to match the antenna impedance (in a small antenna
usually a few ohms) with the receiver/transmitter 50 ohms resistive
impedance.

A pi (series L with C to ground) or a T (series C and L to ground)
will do the trick for a narrow band application.