Topband: Adding a parasitic reflector to a vertical

[Tree]

Back about 10 years ago - I played around with a parasitic element and had
good results.

One method I used to determine how well - and where the antenna worked was
to use a wide band noise source.  You can build one - or I know Elecraft
has one.  For long distances - I would use my amplifier to make it louder
(only do this during the daytime).  You can then put a receiver on the back
side of the antenna and quickly find the frequency where you have the best
rejection (front-to-back).

I feel the main drawback of the parasitic elements is that they work over a
pretty small portion of the band.  This is probably okay for DX work - but
if you are doing contests and need to go up the band some, your performance
will quickly drop off.

Tree N6TR

On Mon, Jan 29, 2018 at 10:40 AM, N7DF via Topband <topband at contesting.com>
wrote:

>
> From southcentral New Mexico working Europe on 160 meters is pretty much
> an exercise infrustration with a single vertical antenna. So I decided to
> see if I couldimprove on things by adding a parasitic reflector element to
> my cage antenna.  Since I could not find any specificinformation about
> doing this I decided to experiment a little and see what Icould come up
> with.  After looking at a lotof designs for two element antennas and taking
> into consideration the physicalparameters of being in a juniper forest I
> finally came up with a design that Icould build.  My antenna is a
> Collins27W-1X conical monopole fed with an MFJ 998 remote tuner located in
> a 120 footdiameter clearing. The parasitic reflector would be 88 feet
> southwest of the monopolein a small clearing.  From what I coulddetermine
> from various sources, in order for it to be effective at thatdistance, it
> would need to be resonant at 1.787 MHz to provide maximum gain at1.825
> MHz.  The reflector elementconsisted of a 30 foot tall section of 2 inch
> diameter irrigation pipe restingon a plexiglass sheet with a top hat wire
> strung at right angles to the linebetween the transmitting antenna and the
> reflector.  In the opposite direction a ground radial waslaid out along the
> ground surface.  Aftera lot of measuring with an antenna analyzer and
> cutting to length the top hatwire ended up as 86 feet 4 inches long and the
> ground radial at 112 feet 3inches to get resonance at 1.787 MHz. The bottom
> of the vertical is connectedto the ground radial with a clip lead so it can
> be taken out of the circuitwhen I want the monopole to be omnidirectional.
> The array turned out to be veryeffective in changing the pattern of the
> monopole and there is a markedimprovement on signals from the northeast
> both in North America and from Europeas realized in the recent 160 meter
> contest. The best measure, though, turned out to be courtesy of WD5COV who
> isabout 125 miles southwest from me.  Hissignal is usually about 40 over S9
> when he has his 4 square pointed myway.  After installing the
> parasiticelement his signal dropped to about 20 over S9 on peaks.
> Unfortunately the antenna has not improved mynoise problems but that is
> another story.
> N7DF
> _________________
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