Whilst Jim Lux and Jim Brown joust over whether it's phasing, polarity, or time
delay,
I would assert that a time delay which is equal to a 180 degree phase
transition at the
frequency in question IS a phase delay.
And that brings me back to where I THINK this particular nit began to be
picked....
If you have two LPDA's, and they're on the tower with the upper one tilted
down, and
the lower one tilted up, and you're able to produce .5 lambda spacing over the
full octave
range of the antenna by virtue of that tilt.....
AND, if the feed system to the dipoles is a parallel transmission line.
THEN I would assert that simply reversing the phase (ok, polarity if you like)
of one of
the antennas AT that feedpoint will result in the two either being IN or OUT of
phase.
At the risk of invoking the voice of the dead, Cebik felt that was correct.
Am I missing something?
N2EA/Jim
and the JIM^2 jousts are below, if you've not seen them...
From: jimlux <jimlux@earthlink.net>
Subject: Re: [TowerTalk] Phase, Time, and Polarity -- Let's Get Our
Words Straight
To: "Tower and HF antenna construction topics."
<towertalk@contesting.com>
Message-ID: <4B5A9096.6020202@earthlink.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Jim Brown wrote:
> On Fri, 22 Jan 2010 20:16:59 -0800, jimlux wrote:
>
>> If you have a time delay between the two antennas (as opposed to a phase
>> shift), then the time delay sets the angle, frequency independent. Since
>> most folks use a hunk o' coax for the phasing, then you're good to go.
>
> Actually, the coax provides a TIME offset, NOT phase shift. There is a
> resulting phase shift from a TIME offset, that is proportional to
> frequency.
Yep..
>
>> If you're using phase reversing (e.g. in phase, out of phase) then it
>> doesn't work as well.
>
> When you reverse the wires in a system, you are not changing PHASE, you
> are changing the POLARITY. When you reverse the polarity, there is NO
> change in time (or delay) or phase, but you invert the waveform, and the
> signal is complex (fundamental plus harmonics, or carrier with
> sidebands), the signal is inverted at ALL FREQUENCIES.
Good point. I was careless.
In any case, phase reversing has a different sort of effect from a time
delay cable.
------------------------------
Message: 3
Date: Fri, 22 Jan 2010 23:00:14 -0800
From: "Jim Brown" <jim@audiosystemsgroup.com>
Subject: Re: [TowerTalk] Phase, Time, and Polarity -- Let's Get Our
Words Straight
To: "Tower and HF antenna construction topics."
<towertalk@contesting.com>
Message-ID: <20100123070016.3E5D35814A@gw1.nlenet.net>
Content-Type: text/plain; charset="us-ascii"
On Fri, 22 Jan 2010 22:00:54 -0800, jimlux wrote:
> phase reversing
There you go again! Wash your mouth out with soap, and say after
me, POLARITY, POLARITY, POLARITY, . . . . . . Hey -- if audio guys
can learn it, why not RF guys?
73,
Jim K9YC
----------------------------
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