Harold: thanks for the electrical lesson.
Umm... three phase electricity.
Latest of locomotives with a.c traction motors were three phase to control the
jerk-forward snap-back action of the first series of a.c. traction motors that
would curl your hair when they did just that.
So... I understand three phase principle (in action no less,) but it was not a
requirement.
Fwiw, GE locomotives have twin turbo Asea-Brown-Boveri engines, 6k horsepower,
at just above stall I have seen 1400-1600 amps at 2+k volts several times on
the readout screens heading for six 1k horsepower traction motors.
Gary
----- Original Message -----
From: Harold B. Mandel
To: wa6fgi@sbcglobal.net
Cc: amps@w4zt.com ; Amps@Contesting.com
Sent: Monday, March 21, 2005 1:15 PM
Subject: Re: [Amps] Measuring RF Power
Dear Gary,
You're acquainted with 3-phase electricity, yes?
Imagine looking down the edge of the wire and seeing
waveforms, infinitely thin, popping out at 0, 120 and 270
degrees. Kind of vector-ish, not really quantifiable, just
an image.
In cellular radio, look down that same wire and see
128 waves popping in and out, but this time, they
wobble, sometimes at their peaks, sometimes while
going up or coming back down.
The NTSC television system has a "vectorscope"
for lining up the correct color bursts when setting up
a multi-camera shoot, so that everybody's Cyan, etc.
is Cyan, etc. It's kind of the same picture: rotational angles,
magnitudes.
In GSM cellular radio, the display that's supposed to be
"textbook" looks like my three year old grandson was
given a pencil and told to scribble inside a circle.
However, each of the vectors is precise, and what makes
us field people crazy is that a 5% phase angle error,
(that CAN be caused by a poor coaxial fitting), can lead to
a 10% desensitization of the corresponding receive channel.
The Agilent power meters are now a steal at $14 thousand
apiece. They're five across, three up and about ten down,
and have all sorts of internal software to come up with
an "average" power display. I saw one technician use a
Bird 43 and measure 22dB, then use an Agilent and came up
with 68dB. Needless to say, all Bird 43's are toast in GSM.
Hal
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