On 11 Dec 2010 23:28:18 GMT, Sébastien MEDARD wrote:

For now, I tried a lot of different things... The best result were on
loops.

Hi Sebastien,

This is a good lesson.

A big loop (1.6mx4 = 6.4 meters), one turn, with an air variable
capacitor + an inside loop connected to the coaxial cable seems to give
better ways to give something to eat to my receiver.

This is an excellent antenna for BCB and Tropical Bands.

Sometimes my air
capacitor was not powerful enough, in the lower bands if I remember
well... To improve that I will have to add a fixed capacitor (lets say
300pF) in parallel (to be bypassed) or more depending on the band I am
listening to.

This is a great solution.

For now I am just experimenting (with some simple wire),
but I think I will build a more solid one...

A big loop (1.6mx4 = 6.4 meters), one turn, with the the universal balun
from Wellbrook. Don't know why, but, it gives very good results, far
better than a long wire in my flat, or a short wire on my balcony... At
this time it seems there is a Ham Contest in Italia... I can get them
fully on 80m LSB/CW/RTTY... Well I live in South of France, so it is
easier for me ))

The reason why this antenna performs so well is that it incorporates
the tuning function in the large loop - the smaller loop does the
matching. In other words, the large loop wire and the capacitor will
reject signals that could overpower your radio and create AGC that
reduces its sensitivity. It is, in effect, a tuner as we have already
discussed. It also happens to be your antenna too.

But the first solution seems more efficient. Need to do further
investigations....

One point to consider, this large loop will not perform the same when
its diameter is large when compared to the wavelength you are tuning
to. Your longwire with tuner will probably be better in the 50M band
and higher. However, experimentation may prove different, especially
if you can tip the loop over (or change its angle to earth).

73's
Richard Clark, KB7QHC