> In my building experience over the years with this choke
> (RF
> Parts/Ameritron), I have never seen one resonate below
> 11.5 mhz or go above
> 12 mhz in all manners of positions and various layouts. It
> is a non-issue.
The actual specs for that choke place the "freespace" series
resonances at 11.8 and 16.8 MHz.
With a wall 1 inch away the series resonances move to 10.8
and 15.4 MHz.
It is 275uH minimum on 1.8 MHz, 375uH on 3.75 MHz, and has a
peak impedance of 30K ohms on 7 MHz.
> I think that the reason Alpha and others use 2 chokes to
> cover all 9 bands
> is that they had a space restriction in the layout. The RF
> Parts choke is
> larger than most.
I think they also don't believe that winding gaps can be
used to position series resonances.
When I designed that choke I used positioned gaps to move
unwanted resonances out of 28, 18, and 10 MHz.
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