Topband: Inductors vs. NORD and UG top loaded antennas

[Tom Rauch]

> Have you found any ratio of diameter to length for a loading inductor
> that optimizes the Q? 

Optimum L/D varies with the required inductance, and about a dozen 
other things.

The most comprehensive text in general publication is in Antennas and 
Transmission Lines  by John Kuecken. It was out of print but is being 
reprinted by MFJ now.

There is a chapter on reactance limits and loading antennas.

In short:

As the inductance is less you need a square L to D ratio, with turns 
spaced about one turn diameter. 

As inductance is very high, like in a mobile whip on a very low 
frequency, the L to D becomes 4:1 or more.

There isn't any real constant, except the turns spacing is always 
around one turn diameter for the gap in round conductor coils (much 
wider in edge wound coils).

All of this is somewhat unimportant because the ground loss is the 
biggest problem, any decent coil would be Q>300 and I've never seen 
one higher than 900 or so at HF.
73, Tom W8JI
W8JI@contesting.com