[Lowfer] re Overall antenna efficiency

[Alan Melia]

Hi all....look out Alan is mounting his hobby-horse again :-))

First I would support JB..... the direction of radials that are so short
(compared with the wavelength) would have not difference to the radiated
azimuthal pattern...........unless by some quirk of fate you manage to
couple into some buried pipes or cables that run of site and are a lot
longer.

The advantage of "radials" ....at this length ground wires is a better term
is very dependent on you local ground. Whilst watching the antenna current
is a useful guide the best way to do the test is with a simple aerial bridge
where you measure the loss resistance. The radiation resistance is so small
it is swamped. This is why it is 'dangerous' to extrapolate from 160m. LF is
a decade away and we all know there can be quite a difference in the way
things perform over that kind of range.

The problem with monitoring the antenna current is that you dont really know
why it changed ....hopefully the loss resistance dropped but the figure
quoted suggest that the improvement if it all went into radiation was about
0.5dB or 10%. But did the tuning change and cause the PA to run more power,
has the antenna just got a lower feed impedance? Is the extra current
traversing the radiation resistance. To get real advantage you need to be
looking for more than that.....but it might now be attainable within your
local contraints.

The best test is to establish a test location about a mile away and make a
strength reading there. If the received strength has increased then you have
made an improvement (assuming your measuring gear is stable)

Above all make sure you use your effort efficiently because it is easy to
get discouraged by going round in circles trying to replicate someone else's
results which may not be applicable to your location, get fed-up and leave
the band. But as Andy has found out there are lots of things to learn and
lots of fun to be had learning them.

Alan G3NYK