Very good. Furthermore, following your ideas, the diameter of the wire at
a current anti-node could be infinitely thin!

Malcolm

"Reg Edwards" wrote in message
...
Malcolm said -
But do you
really need 14 awg?
Wouldn't 16 awg do?

===================

Yes, but you wouldn't be saving so much by NOT using tapered copper wire.
It's a mind-boggling matter of economics. If tapered wire WAS
manufacturable
I'm sure there would be a mad rush by suckers with more money than sense
to
buy Specially Tapered Low-loss G5RV's including the transmission line.


Actually, for a complete professsional design, the distribution of current
along the antenna wire should be taken into account when considering wire
diameter. It affects radiating efficiency. Only hot-spots need be
considered.


Working backwards, take an 80m 1/2-wave dipole using 20 awg enamelled
copper
magnet wire (my favourite stuff). At 3.75 MHz the resistance of 20 awg
copper wire is 0.206 ohms per metre. Overall end-to-end dipole resistance
=
8.24 ohms.


Now take a 1 KW transmitter. The current AT THE DIPOLE CENTER =
Sqrt(1000/70) = 3.74 amps.


Radiating efficiency = 140/(140+8.24)*100 = 94.4 percent, where 140 = 2*70
is end-to-end distributed radiation resistance.


At the dipole centre the power dispated in the middle 1-metre length of
wire
= 3.74^2 * 0.206 = 2.88 watts corresponding to 73 milliwatts per inch of
wire. If you have a brain-surgeon's sensitive finger tips this will feel
slightly warm and nothing to worry about.


A radiating efficiency of 94.4 percent corresponds to an undetectable loss
of 1/25th of an S-unit relative to perfection and no sleep need be lost on
this account either.


The foregoing implies that antenna wire diameter depends more on wind
speeds, ice formation, and the cost of the pair of masts needed to support
it. Recently educated Ph.D's having difficulty with arithmetic may leave
the hard bits for later reading.
----
Reg, G4FGQ