Topband: Folded wire verticals

[Maurizio Panicara]

N4UH:
> If radiation resistance is the same as input resistance per
> item 4 above, antenna efficiency can be increased
> effectively by using multi-folded wire verticals, making
> ground and other losses negligible factors.

Hi Henry,

I think you're mixing up radiation resistance with feed point impedance.
The Rr of the aerial is related with its electrical height and doesn't
change if the radiator is series or shunt feed.
A splitted dipole in free space is 73 Ohm likewise a folded (or multifolded)
dipole.
Imagine the folded antenna as an electrical circuit and shorten the
generator to evaluate it.
The folded vertical can be easily seen as a single but thicker conductor.
The same considerations obviously apply in case of multi folds wire fans.
With a thicker aerial some of the resistive losses is reduced and in theory,
feeding the fold in a folded radiator produces the same fattening effect and
leads to the same efficency, Rr and losses.
In my opinion, anyway, shortening the folds at base and series feeding the
aerial it's easier to approach maximal performances althoug shunt feed is
often more practical to be realized.

73,
Mauri I4JMY



--
FAQ on WWW:               http://www.contesting.com/FAQ/topband
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Problems:                 owner-topband@contesting.com