[TowerTalk] what size wire for kilowatt TX ??

[Martin Ewing]

I'm not buying that!  Current flow depends on impedance, R+jX, not radiation
resistance. Your short whip runs at high voltage and low current.  There is
lots of current in the matching network, but little gets into the antenna
wire.  Another way to see it is that the "boundary condition" on current
flow is that it must be zero at the end of the wire (unless there are sparks
flying!).  Transforming back a fraction of a wavelength to the feed point,
you're still mostly voltage and little current.

A small loop antenna is the complement, mostly current and little voltage.

73 & Cheers,
Martin AA6E

On Sat, Jan 3, 2009 at 4:46 PM, Steve Hunt <steve at karinya.net> wrote:

> Nope - the current will be much higher in an electrically short antenna.
> What matters is not its high reactance - that will get tuned out by the
> matching circuitry - but the low radiation resistance where the power is
> being dissipated. If you don't believe it, just picture how much current
> is flowing in a small magnetic loop antenna or a mobile whip.
>
> 73,
> Steve G3TXQ
>
> Martin Ewing wrote:
> > This all assumes you're talking about a full size dipole.  If your
> antenna
> > is more like a short whip, the current in the wire is much less, since it
> is
> > a high impedance antenna.  Then, your problem is in the antenna
> > tuner/coupler and ground system, where there could be high losses.
> >
>
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-- 
Martin Ewing, AA6E
Branford, CT