Mike,
Thanks for your excellent clarification of the Vin vs Iout phase delay of 90
degree transmission lines.
For those interested in further pursuing this important phased array
topic, W8WWW's web site presents an easily understood description of
how to use -- and misuse -- 90 degree transmission lines in phased
arrays.
http://www.seedsolutions.com/gregordy/Amateur20Radio/Experimentation/HexArray/HexPhase.htm
73
Frank
W3LPL
---- Original message ----
>Date: Tue, 17 Apr 2007 22:38:56 -0700
>From: "Michael Tope" <W4EF@dellroy.com>
>Subject: Re: [TowerTalk] 135deg cable
>To: <towertalk@contesting.com>, "Pete Smith" <n4zr@contesting.com>
>
>
>----- Original Message -----
>From: "Pete Smith" <n4zr@contesting.com>
>
>>> > 2. if the line length is any multiple of exactly 90 degrees, its
>>> phase delay is the same as its electrical length and the phase delay
>>> > is not dependent on the VSWR on the line.
>>> >
>>> >
>>>I don't think this is true. My old memory says the length is 180 deg.
>>>
>>>73, Roger
>>
>>
>> You're right. On page 11-7 of the current edition of the ON4UN book, Fig.
>> 11-6 charts phase shift vs line length for various load mismatches. For a
>> given mismatch the phase error appears greatest at 90 degrees and zero
>> only
>> at 0 and 180 degrees.
>>
>> 73, Pete N4ZR
>>
>
>Pete,
>
>Figure 11-6 shows the "current phase shift" of a 50 ohms line
>versus electrical length for 3 cases (1 matched, 2 different
>mismatches). This is equivalent to ANGLE (Iout | Iin). With
>the 90 degree line ANG (Iout | In) <> 90 deg is VSWR <> 1.0,
>but ANG (Iout | Vin) = 90 deg for any load impedance. See
>paragraph 3.4.5 on W7EL "Current Forcing" properties of 90
>degree lines.
>
>73, Mike W4EF........................................
>
>
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