[TowerTalk] Wire antenna?

[Richard (Rick) Karlquist]

On 7/1/2019 10:21 AM, jimlux wrote:
> On 7/1/19 8:18 AM, john at kk9a.com wrote:
>> It needs no tuner or counterpoise and it has great eham reviews!  How 
>> does this work?
>>
>> John KK9A
> 

I've done a fair amount of work with end fed half waves.  They
make a fair amount of sense on the frequency where the wire is
at half wave resonance.  On the frequency of full wave resonance,
they still make sense because they are two half waves in phase
and behave similarly to a half wave dipole.  However, the frequency
of full wave resonance is not exactly twice the frequency of half
wave resonance.  This means that if you try to operate it on two
adjacent ham bands that are nominally at a 2:1 ratio, it will typically
resonate too high for the upper band or two low for the lower
band.  You can still use it on 2 bands, but then you will need a 
counterpoise because the drive impedance is no longer extremely high. 
So the EFHW is primarily a single band antenna, or maybe 2 bands.

Beyond that, the marketing idea of a multiband end fed wire is just
a fantasy.  The pattern on the higher bands will be full of lobes,
and the drive impedance will be all over the place.  Ignore reviews
by low information users.  You would be advised to have a separate
EFHW for each band.

The best thing a wire antenna user can do is to make all wire
antennas monoband.  Most of the mischief having to do with wires
occurs when people attempt to broadband them.

Rick N6RK