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Author Topic: Vertical Antenna Director  (Read 2437 times)
W4OEQ
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Posts: 140




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« on: September 21, 2012, 05:59:50 AM »

I have a Hustler 4BTV vertical with ground radials.  Works fine.  I am wondering whether one can add a second vertical pipe (no loading coils) of appropriate length and spacing to create a director.  Has anyone tried this?  73,  Tom, W4OEQ 
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K1CJS
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« Reply #1 on: September 21, 2012, 06:24:03 AM »

It is possible.  I've helped work on a repeater system that is located near the ocean, and the general thought was to use another antenna as a reflector to push the radiation pattern inland.  In the end it was not done, but the person in charge (a radio engineer) had plans and computer models that showed the concept was possible.
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WB6BYU
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Posts: 13287




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« Reply #2 on: September 21, 2012, 08:28:53 AM »

Sure, you can make either a director or reflector that way, or both.  You could
even have them arranged in different places for each band.

I remember seeing an article where a ham made a number of mounting points
around his vertical to provide manual rotation (moving the parasitic element
to a different mount).  The movable element had a loading coil that allowed
to be tuned as either a director or reflector on each band.

A friend of mine is doing this with with his vertical, which is mounted in a
flower bed in the middle of a circular driveway:  he is putting a 40m parasitic
element (nearly full sized) on his truck so he can park it anywhere around
the antenna.
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WB2WIK
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« Reply #3 on: September 21, 2012, 11:27:31 AM »

The problem with this is that any length and spacing of passive reflector or director you choose will only work on the one band it's set up for.  I doubt it's possible to get that to work on all four bands.

However, for the same effort as installing a passive parasitic element, you could install another 4BTV!  Then, using a remote switching system to change the lengths of interconnecting phasing lines, you could "steer" those antennas remotely (turn a knob in the shack) and make it work on all four bands if you do it all right.

The latter system is more complicated and normally involves several cables and relays, but there are commercially built accessories to do that (for $$), or it could be a homebrew job that should survive the WX if it's built well.
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W8JI
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« Reply #4 on: September 21, 2012, 02:26:19 PM »

I have a Hustler 4BTV vertical with ground radials.  Works fine.  I am wondering whether one can add a second vertical pipe (no loading coils) of appropriate length and spacing to create a director.  Has anyone tried this?  73,  Tom, W4OEQ 

A reflector is nearly perfectly tuned when self-resonant just below the lowest frequency in the band, and it is fairly independent of spacing within a range of .1 to .25 wavelengths. It is the most non-critical element.

I don't see why a properly adjusted second trap vertical couldn't be used as a reflector on at least two bands. It would not have a of gain, maybe 3-4 dB.
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W4OEQ
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Posts: 140




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« Reply #5 on: September 21, 2012, 05:22:02 PM »

I appreciate the comments.  My vertical is mounted among some trees.  In some directions, a director would be appropriate and in others a reflector would be required.  At this point, I merely want to experiment with a single band, either 40m or 20m.  It would be great if I can find a solution that does NOT require a loading coil.  I could easily mount a small pipe.  Wouldn't it also be possible to suspend a wire of appropriate length from a conveniently located tree limb to serve this purpose? 73, Tom, W4OEQ
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WB2WIK
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« Reply #6 on: September 21, 2012, 06:36:10 PM »

If you want to "steer" your vertical in various directions, a single director or reflector won't do that.

Using a second vertical with variable phasing between them will.
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W9GB
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Posts: 2623




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« Reply #7 on: September 21, 2012, 07:07:11 PM »

Quote from: W4OEQ
I have a Hustler 4BTV vertical with ground radials. I am wondering whether one can add a second vertical pipe (no loading coils) of appropriate length and spacing to create a director.  Has anyone tried this?  73,  Tom
Tom,

As you drive along the highway, you pass directional AM broadcast stations (daytime/nighttime) that use multiple towers (their vertical antennas/radiators) to produce specific transmission patterns during the DAY, and differing patterns at NIGHT.  550 - 1700 kHz (above 200 meters)

You also pass thousands of Land Mobile Radio (LMR) service and amateur radio fixed stations and repeaters that use 4 or 8 dipoles on a single mast/tower.  140 - 170 MHz // 400 - 470 MHz (2 meters and 70 cm).

From this:

1.  You realize that Wavelengths matter in the shear size of antennas
2.  ANTENNA PHASING is how this is accomplished in both examples.
3.  AM Broadcasters and most LMR stations operate on ONE FREQUENCY, or closely coupled frequencies ----
this simplifies the usage and tuning of PHASERS.
4.  Amateur Radio's Multiple frequency allocations and frequency agility (due to changing propogation conditions) while sometimes an advantage ... Can be a disadvantage for aspects such as this.
==
There are systems to explore this area of vertical array antennas, such as:  Array Solutions
http://www.arraysolutions.com/Products/phasedarrays.htm

w9gb
« Last Edit: September 21, 2012, 07:15:18 PM by W9GB » Logged
WX7G
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Posts: 6078




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« Reply #8 on: September 21, 2012, 07:30:22 PM »

A parasitic element will raise the antenna current in the driven element along with inducing current in the parasitic element. A low loss ground system is needed so that all of the gain is not consumed in ground loss. Of course the system, even with ground losses, will be directional.

A nice way to go if you have the space is to phase two verticals 1/2 wavelengths apart and feed in-phase to form a broadside antenna having a gain of 3 dB. The antennas are far enough apart to have essentially no mutual coupling. Feed 180 degrees out-of-phase and you have an end fire array.
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W4OEQ
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Posts: 140




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« Reply #9 on: September 21, 2012, 08:59:45 PM »

Good suggestions.  Here is a simple way one QRP ham tackled the question:

http://www.n0lx.com/phased.html

But, he did not start with a 4BTV.

73, W4OEQ
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K3ANG
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Posts: 178




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« Reply #10 on: September 21, 2012, 09:03:43 PM »

Go to http://www.hy-gain.com/pdffiles/AV-18VS.pdf
It's the installation manual for the Hy-Gain AV-18VS vertical antenna.
It has a section on phasing verticals for single and multi-band use.
Go to page 7 and read to the end.
This will give you an idea of what's involved to phase verticals.
73
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WA2TPU
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Posts: 209




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« Reply #11 on: September 21, 2012, 09:09:22 PM »

to WX7G and all who posted.

Its nice 2 C all these sincere thought-out postings. Thanks.

I'm using the WX7G Bobtail on 30 meters and it works quite well. I wonder if anyone has tried to take a pair of Steppir verticals and phase them....steer them. That would be interesting to hear about those results.

Best regards and many 73.
Don sr. - WA2TPU - A TRUE 5 WATT QRP GREEN STATION.
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W4OEQ
Member

Posts: 140




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« Reply #12 on: September 22, 2012, 06:25:10 AM »

I appreciate all of the suggestions and explanations.  Thanks to K3ANG for the reference to the Hy-Gain manual and its clear explanation of alternative approaches.  I see some possibilities worth pursuing.  73, W4OEQ
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