Hi Tom,
Your question has been discussed many times on TowerTalk.
Coaxial lines can NOT simply cut coaxial lines to produce 72 and 80 degree
phase delays in an array of phased verticals, because the phased array places
significant VSWR on the phasing lines. The phase shift in any coaxial line is
a factor of T W O properties:
- physical length, and
- VSWR
If you have an dual trace oscilloscope, its very easy to observe this property
of a mispmatched transmission line, by varying the termination impedance of the
line and observing the change in phase shift.
A coaxial line will produce a delay equal to its electrical length only if its
VSWR is 1:1, except for the special case where its electrical line length is 90
degrees (1/4 wavelength) or any multiple.
73
Frank
W3LPL
---- Original message ----
>Date: Sun, 01 Jun 2008 16:04:44 -0700
>From: "Tom Osborne" <w7why@verizon.net>
>Subject: [TowerTalk] Phasing lines
>To: "Towertalk" <towertalk@contesting.com>
>
>Hi All
>
>If 90 degrees is 360/4 (1/4 wave) then is 72 degrees 360/5 (1/5 wave)?
>
>Would that make a 72 degree phasing line 23.4 feet (133/5 * .88)?
>
>Then an 80 degree phasing line would be 26.1 feet (133/4.5 * .88)?
>
>I am actually trying to figure 80 and 71 degrees lines for 40 meters using
>RG8X.
>
>My high school math is buried somewhere in the back of my brain.
>
>If this is true, how can I find which frequencies these would be a 1/4 wave
>at so I could use the analyzer to cut them to length?
>
>I want to make phased verticals with an 80 degree feedlines with a 71 degree
>phasing line. 73
>Tom W7WHY
>
>
>
>
>
>
>
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