Don't know about the WX0B stackmatch but with the Comtek phasing box you use
1/4 wavelength 75 ohm low loss coax for the lines from the box to the
elements (I believe these are impedance transformers) and you do want the
shields connected. However, in a parasitic array, where you drive only one
element and the other elements become reflectors, you do want the shields
isolated.
The way my neighbor did it was to feed each element with 3/8 wavelength of
RG-213 through a relay box. This relay box would open both the center
conductor and the shield of the reflectors, which would cause them to become
inductive and work as reflectors. And he did this with 2, 3, 4 and 5
element arrays, and they worked. We did besideya comparasions between his
4sqP's and my 4sq phased arrays and the performance was identical as near as
we could tell, with the exception of feed point SWR. My 4sq phased arrays
are effective over a relatively large bandwidth however I believe the
parasitic array loses it's F/B if pushed in bandwidth. That is, my 80m
array is tuned for 3525 and is effective at 3800, but I believe the
parasitic arrays pattern will get wierd if you try that.
And if he left the shields connected the array became a giant vertical.
de Paul, W8AEF
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ZF2TA ZF2JI FO8DX FO0PLA 8Q7AA XZ0A
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----- riginal Message -----
From: <K3BU@aol.com>
To: <towertalk@contesting.com>
Sent: Tuesday, January 13, 2004 2:25 AM
Subject: Re: [TowerTalk] Problems on a 2el vertical Array
In a message dated 1/12/04 7:06:53 PM Eastern Standard Time,
T.Wellnitz@gmx.de writes:
Yuri, you don't have to disconnect the shields. All you need is to shorten
the inner and outer conductor if the phaseline is about 80°-100°
(electrically)
long or have an open feed line for 170°-190°.
You do if you want the triangular array perform the way it is supposed to
work with WX0B stackmatch.
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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