[TowerTalk] rotary dipole 30m.

[Jim Lux]

At 09:48 AM 10/5/2005, Peter wrote:
>Hi there,
>
>does somebody knows a good link to a webpage,
>for some info's how to build a rotary dipole for 30m.
>Using alu. tubes,with traps and total lenght around the 30feet perhaps.
>

What about adapting one of the many "shorty forty" designs?  Basically, a 
loading coil in the middle, with the taps chosen to get the right impedance.

For reference, a 10 meter long copper wire, 1mm in diameter, suspended 30 
meters above soil with 5 mS/m conductivity, and epsilon=13, has a feedpoint 
impedance of about 27-527j ohms..  In the classic shorty forty scheme, 
you'd have a air core autotransformer to do the matching.  The X doesn't 
change all that fast:

at 10.0 MHz, 26.4 -548j
at 10.3 MHz, 27.7 -506j

>Kind regards,Peter ON7BJ.
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