[TowerTalk] Fan dipole construction methods

[Joe Subich, W4TV]

> Ideally (and this may be too many wires to be practical) I would like
> to construct an 80/60/40/30 meter fan dipole requiring only a single
> rope at each end. Major project is OK if the end result is viable.
I would not recommend a parallel/fan dipole with 80/30 meters.  I've
tried it several times and the 80 meters wire detunes 30 meters.  The
antenna works as badly as if one simply used a tuner to force power
into the 80 meter wire.

*IF* I were going to try an 80/60/40/30 combination, I would get two
sets of traps (Reyco KW40 and KW30) and build a fan of trapped
antennas.  One antenna would be 80/30 meters (the traps isolating
the 30 and 80 sections) the other would be 60/40 meters.  However, I
am not comfortable with the behavior of 60 and 80 meters in parallel.

The better "solution" for fan dipoles would be two fans - one for
80/40 and one for 60/30 where one has a harmonic relationship between
the two bands in the antenna.

Parallel/Fan dipoles work because the lower band antennas represent
a *high impedance* across the feed point of the active band antenna.
When one has a fan in which the bands are not harmonically related,
that high impedance relationship is upset and the "inactive" wires
now present significant inductance/capacitance in parallel with the
feed point.

73,

    ... Joe, W4TV


On 10/1/2017 7:21 AM, N1BUG wrote:
> I've been reading the fan dipole discussion with much interest. I have 
> used fan dipoles for many years, as inverted V, common center point with 
> the ends tied off separately. The biggest one (a club project) had 6 
> wires for 160/80/40/20/15/10. It worked OK but that was a lot of rope! 
> Currently I have individual inverted V antennas for each of several 
> bands all supported from various points on one tower. I would like to 
> reduce the number or ropes tied off everywhere.
> 
> If you have successfully constructed and used a fan dipole where one or 
> more more wires hang from the first and each end requires only a single 
> support rope I would like to see details of the construction. I have 
> made a few attempts and seen some others but they all either suffered 
> from the lower wires sagging, constantly breaking spreaders or both.
> 
> Ideally (and this may be too many wires to be practical) I would like to 
> construct an 80/60/40/30 meter fan dipole requiring only a single rope 
> at each end. Major project is OK if the end result is viable.
> 
> 73,
> Paul N1BUG
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