[Elecraft] Miniature self-supporting HF antennas

[David Gilbert]

Exactly, although of course a coil at the very top sees no current so 
doesn't do any good there unless there is some capacitive loading above it.

Dave  AB7E


On 7/20/2015 2:44 PM, Jim Brown wrote:
> On Mon,7/20/2015 1:56 PM, David Gilbert wrote:
>> It all depends on the rest of the antenna, and yes, a very short 
>> antenna with a crummy coil in the wrong place is going to suck.  But 
>> some of the best antennas on the market right now use coil loading 
>> very effectively.
>
> There was an excellent piece in QEX a year or two ago devoted to the 
> design of short loaded antennas. It was published in two parts -- one 
> dealt with measurement, the other with studying the effect of the 
> position of the loading coil.
>
> The executive summary -- the part of the antenna carrying the greatest 
> current does the most radiating, and for most short antennas, that's 
> the part of the antenna closest to the feedpoint. The current 
> distribution depends on the electrical length, including that coil. A 
> loading coil near the feedpoint seriously degrades the radiation 
> efficiency of the antenna, because the current maxima is in the coil, 
> but the coil doesn't radiate! SO -- loading should be as far as 
> possible from the feedpoint! All of this was borne out by the 
> measurments.
>
> 73, Jim K9YC
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