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Old November 18th 13, 05:43 AM posted to rec.radio.amateur.antenna
Jeff Liebermann[_2_] Jeff Liebermann[_2_] is offline
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Default Noise susceptibility of a 2m yagi

On Sun, 17 Nov 2013 22:26:53 +0000, Channel Jumper
wrote:

Why not just raise the antenna higher?


Because that will pickup more noise by reducing the number of
obstruction between the noise sources and the antenna (and coax
cable).

Most ambient noise is vertically polarized.


Most man made noise is horizontally polarized because it is
re-radiated by power lines, which are horizontal. A good example is
electric motor noise. By the time you get to VHF frequencies, noise
sources are random, mostly due to multiple reflections.

Incidentally, "ambient" noise is usually used in reference to audio
notice levels, not RF.
http://en.wikipedia.org/wiki/Ambient_noise_level
I suspect you meant atmospheric noise and/or man-made noise.

This is the reason why television is horizontally polarized.


TV is horizontally polarized because the first FM operated in the
42-50 MHz region, where horizontally polarized antennas were more
common. A vertically polarized 30 MHz Yagi would be quite
impractical. The first TV stations were 44-50 MHz, and later moved to
50-56 MHz. Same problem... a vertical Yagi would be too big. There
are some other reasons if you want more detail.

Use a poly phaser and ground to dc.


Polyphaser makes lightning arrestors, which are of no use in
eliminating or reducing noise pickup.

--
Jeff Liebermann
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