Jerry Martes wrote:
Roy

Since I consider antenna efficiency difficult to measure accurately, I'd
be willing to try to measure it as carefully as *practical*. If that
required that the referance heater had a similar "thermal mass" to that of
the antenna under test, I could probably make a heater that did have a
thermal mass equivalent to that of the antenna.
But, I would propose that there is no easier way to actually measure an
antenna's efficiency than to measure the amount of power it turns into heat.
Thats a statement I cant back up, and I know it.

What is a better way to measure an antenna's efficiency??


I believe it would usually be easier and more accurate to measure the
amount of power it turns into radiation. That is, measure the strength
of the radiated field compared with an antenna of known efficiency and
preferably having a similar pattern.

Neither is easy, and a method that's "practical" from your point of view
might well yield results which are so grossly inaccurate as to be
useless. But go ahead, do a careful estimate of the accuracy you expect,
do some measurements of various simple antennas whose loss is easy to
calculate and compare the measured results, and see how well you can do.
It's probably within the reach of a very careful amateur to make
measurements which are accurate enough to be useful. It just isn't easy,
and requires knowing the relationship between heat and temperature,
where the heat is going, sources of error and the amount they can
contribute, and a whole lot of care and attention to detail. And that's
to get even crudely accurate results.

For myself, I'd model it as Reg suggests (although I'd use a program
rather than the back of an envelope as he would) and easily believe that
the model results are more accurate than any measurement I'd be able to
make. However, neither calculation or measurement results are likely to
alter the claims made by manufacturers of miracle antennas and their fans.

Roy Lewallen, W7EL