Coax-through-bead baluns have another advantage.
It is impossible to tell if they have failed from the ground or SWR
reading. The only way I've been able to detect damage is if they
rattle. I suppose what you don't know can't hurt you.
73 de Brian/K3KO
Tom Rauch wrote:
>
> > A balun work's best when it see's a pure resistance, or nearly so. A
> > balun at the end of a piece of coax, feeding a length of balanced line
> > that feeds an antenna, will almost be guaranteed to see a reactive load.
>
> A choke balun cares less if the load is reactive, only voltage baluns
> (like the W2FMI style) are load impedance critical.
>
> > A better idea would be to place the balun at the input of a balanced
> > tuner. If there are difficulties in bringing in the balanced line to the
> > tuner, then a small section of shielded balanced line can be employed.
>
> Placing a choke balun at the input of a tuner does nothing for
> balancing of the system, although it does reduce differential mode
> stress on the balun (which usually isn't a problem anyway if you
> use a properly constructed choke balun).
>
> After some discussion of this in another antenna forum, Roy
> Lewallen (W7EL) did an analysis and confirmed this.
>
> 73, Tom W8JI
> W8JI@contesting.com
>
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