[Elecraft] Less Than Perfect Antennas [was Flumoxed]

[Fred Jensen]

Robert: Yes, most of the radiation from a conductor originates in the 
high current section(s) of the conductor, and for a half-wave dipole, 
that's the center, low impedance part.  The sag will lower the center, 
ergo the "gain" will decrease.  Whether or not it's enough to be 
noticeable is questionable however, and may be off-set by the losses in 
transforming the balanced line to unbalanced and the impedance 
transformation required.  At some point in all this discussion, you will 
find yourself trying to pick the fly poop out of the pepper [military 
expression which I've cleaned up a little for this forum].

Related:  The voltage/current distribution on a conductor is determined 
*only* by the length of the conductor measured in wavelengths.  It 
doesn't matter how or where you inject the RF current.  A Buddipole in a 
horizontal configuration is off-center fed because it is inherently 
physically short and low, and the center impedance is also low ... 
~20-30 ohms on 20 meters.  Moving the feed point out toward one end 
raises the impedance seen by the 50 ohm transmission line.  It also 
unbalances the entire system leading to undesirable current on the outer 
surface of the coax shield conductor.

And, to the original subject I assigned to this thread, how many 
remember the Windom feed that Novices, who couldn't afford transmission 
line, used in the 50's.  Definitely "Less Than Perfect" but there are 
QSO's in my log using it.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 12/8/2018 7:03 PM, Robert G Strickland wrote:
> Ron...
>
> Would such an antenna cut for 80m, fed with ladder-line, and used on 
> 40m, be a better performer on either band than an 80-40m fan dipole 
> fed with 72ohm coax? Leaving all other extraneous but influencing 
> parameters aside. I have the second antenna; the weight of all that 
> wire and the coax with a ferrite balun results in a significant sag. 
> I'm wondering if the first antenna, lighter and higher in the air, 
> would perform better? Thanks.
>
> ...robert
>