On Dec 7, 5:02*am, "D. Heizinga" wrote:
Experience anyone with this one ? * Imagine a vertical half folded dipole.
One side is grounded. Like this:

*o *____________________________
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * l
______________________________l
l
ground.

o = input

Drawn laying down but of course it stands upwards. All is a 1/4 lambda long.
But now the trick: a coaxial cable can be shorted at the end too. But the lenghts needs
only be 0.66 times ! *So 40 metres high becomes only 26 metres.
Don't bother the shielding, that is no obstacle for magnetic fields.

Can't see much point. Makes more sense to just run a 1/4 wave to me.
Sure, the coax has a slower velocity factor than wire, but that's not
going to make a 26m antenna show the same performance as a
wire 1/4 wave. It will still be a "short" vertical vs the monopole.
I'm not sure how the current distribution would be effected.
Would need to model it.. But I'm too lazy to mess with it at the
moment. :/
BTW, there will be some extra loss in the mix using the coax vs
plain wire if you are feeding the center conductor. Much the same as
you would see using a coax dipole such as the common "bazooka".
Also, there is no advantage to using a folded vertical vs a monopole
if avoiding ground losses are the intent.
That used to be a fairly common belief that has been pretty much shot
out of the water in the last several years.
So... Where's the beef?