Hu Luis, |
Am 20.05.2015 18:34, schrieb VIGILANT Luis Fernández:
That is not a good dimension. The length of the coil should be about
the diameter of the coil or at least less than 2x the diameter.
Thank you for your detailed
I can recycle 16cm diameter PVC
tube. As seen in the calculators and assuming a copper wire with
plastic cover to be 3mm diameter
can wind 300 turns in 90cm
lenght which would be 2.33 mH.
A 16 cm PVC tube is a good choice but the 3mm diameter wire is to big.
But of course it is all your decision, i don't want to force you to do
it like i think, i can't do anyway ;-)
Is the mast completely metallic? Or just the first piece? It can be
helpful to lift the coil a bit above the ground, say 50 cm onto non
conducting stuff, to avoid losses. Just leave the tube 50 cm longer
That can be a starting point
and the coil should be attached to the bottom support
of the vertical antenna. See and
old picture here showing the setup
Maybe the WX-station in the picture is grounded? It is a good EMC test
if it can handle 5 A of RF current ;-)
May be 5pF/m is the standard
assumption for a vertical antenna against horizontal ground plane. But
here the counter poise will be different
and probably showing much less
Also your horizontal loop can be a part of a counterpoise.
It can help in first steps, when you still don't know the actual
resonance point, i.e. if you need more or less L. But in the end you
should have no C in parallel. It won't handle the voltage anyway :-) Of
cource this depends on your RF power.
I can use a high voltage
capacitor in parallel with the coil to tune. The variable capacitor I'm
already using with the loop, for
example. Would it make the trick to use a smaller coil ??
If C is 55 pF and your losses are 50 Ohm and the power is 50 W, you
will have 6 kV on the antenna.