[Elecraft] how did I calculate the loss?

[Jimmy Lee]

Don,
Does my 4-1 balun at the input of my K2 introduce losses and if so will  more power
get to the antenna without the balun?


Don Wilhelm wrote:

> Vic and all,
>
> I respectfully disagree.  The balance or lack of balance is dictated by the
> antenna system itself (and the RF will be independent of grounds).  So, if
> the antenna system is inherently balanced, the currents (or voltages if you
> prefer) on the feedline will be equal and opposite no matter what the drive
> is - this is not dependent on a balun or lack of a balun anywhere in the
> system.
>
> Look at it another way - the current at the ends of the antenna must be
> zero - period.  No amount of current 'forcing' will change that - mother
> nature will have her way in this.  If the antenna is unbalanced, the use of
> a balun to "force equal and opposite currents" will only serve to induce
> losses elsewhere in the antenna system.
>
> I realize that this is 'flame' territory, but I do not intend it as such.  I
> am not saying baluns are not good things, but instead, I am saying that
> baluns serve the purpose if keeping extraneous RF currents in their proper
> places - they are not the sole element that will determine the current
> distribution on an antenna system (and that is what is implied by the
> 'current forcing' adherants).
>
> The real reason for a balun at the feedpoint of an antenna is to keep the
> current from flowing down the outer side of a coax shield.  If one is
> feeding an antenna with balanced line, this situation is not present.
>
> At the transmitter (or tuner) end of parallel line, a balun is a 'nicety',
> but not a necessity, because the RF will find its own COMMON potential - as
> I stated earlier, this really can be independent of any actual ground
> potential.  OTOH, if "RF in the shack" is a problem, a balun at the
> transmitter (or tuner) output may cure it.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>
> > I forgot to add...wouldn't you also need a balun at the antenna
> > feedpoint?  If you connect the feedline directly to the antenna the
> > currents in the legs of the feedline could be unbalanced and then you
> > might have significant loss from feedline radiation.
> >
>
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