[Elecraft] Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

[Jim Brown]

On Wed,3/23/2016 7:12 PM, Wayne Burdick wrote:
> I've been using an MFJ-1820T telescoping 20-meter whip for a few months. Considering its length (48"), results have been excellent. I typically use it with the KX3 on a picnic table at 15 W (with an external battery), or hand-held at 3 to 5 W (internal battery).

As Tom Schiller, N6BT, famously noted, EVERYTHING WORKS, sort of. He 
demonstrated this by working all continents loading a lightbulb that he 
fed with coax. Tom is the designer of the excellent Force 12 antennas.

I just did a quick NEC model of a 4 ft vertical with loading coil and a 
single quarter-wave radial laying on the ground, and compared it with a 
quarter-wave vertical (16.7 ft) with the same single radial. The model 
is for poor soil, which is typical of most mountainous QTHs. The 
full-size quarter-wave will be 7.4 dB louder than the shortened one. 
That's equivalent to reducing a 15W signal to 3W. The difference is 
slightly greater over better than average ground. The reduced efficiency 
is due to the greatly reduced radiation resistance of the shortened 
antenna.

Bottom line -- yes, shortened antennas work, sort of, but full-size 
antennas work BETTER. If you can afford the weight of a means to support 
the longer antenna (typically a telescoping fiberglass pole), it's well 
worth it! And if a shorter antenna MUST be used, LONGER antenna, LESS 
coil is better.

73, Jim K9YC