wrote in message
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On Jan 16, 9:17 pm, "Jim" wrote:
"Eisboch" wrote in message

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"Jim" wrote in message
.. .

The definition of peak to peak must have changed since I was in A
school.
I was taught that positive peak to negative peak or negative peak to
positive peak shal be called peak to peak. (Neener Neener)

Sure. I don't disagree. Usually the term "peak to peak" relates to
amplitude measurements. But, a positive peak to the next negative peak
is
180 degrees if you are looking for frequency over a time period. A
positive peak to the next positive peak is 360 degrees. Or negative to
the next negative. Or any other point to the next repeating point on
the
waveform.

Eisboch

360 degrees= 1 cycle is the description I was looking for. Quit trying to
confuse me with facts.
Check tonights Tampa news videos.

OK, for radio waves, there are several straightforward ways to
directly measure wavelength instead of calculating it from frequency.
The easiest is with a waveguide with a variable end. This is simply a
metal tube whose diameter is roughly the wavelength. You adjust the
length of the tube (it should have a sliding metal end) till a
electric field prob in the center measures a maximum indicating that
your wave terminates at the end. Then you move he slide in and you
will find another position where you have a maximum. The distance you
have moved the slide is the wavelngth. The electrical engineers here
can tell you how this relates to SWR etc and all about Smith Charts
but this is a very straightforward physical measurement.
You can also use two vertical antennas each emitting a sin wave of
exactly identical in phase signal. When the two antennas are exactly
one half wavelength apart, you will see a maximum signal along a line
that passes exactly betwen the two antennas.
For visible light, one uses a device called an interferometer to
directly measure the wavelngth. Because such devices are so sensitive
to movement, they are often used to align extremely precise equipment.
For x-rays, one uses crystals where the wavlength is given by
wavelength=2dsin(q) where 2d is the crystal spacing and q is the
reflection angle (I do this every day)
For sound waves, I would use a tube with a variable slider so the tube
would resonate with teh applied sound when the slider is set to the
correct length corresponding to the wavelngth.

Similar to how a CD works. The distance from the laser to the reflective
backing is very close to the wave length. So when it reflects back to the
detector you get a dark spot.