dead spots

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xpawel15x

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Dec 14, 2005
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Is it normal to have these "dead spots" where my scanner is sitting at a position that it doesn't receive any signals?

For example, it receives fine at an upright (standing) position, but when placed down flat it sometimes doesn't receive and as soon as I pick it up again it receives fine again..

I'm using a pro-97 with ducky antenna. Also it happens on the quite weaker freqs, because the really strong signals seem to come in no matter what position the scanner is at.
 

SAR923

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Dec 19, 2002
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Yes, this is quite normal. Since the signals you are trying to receive are vertically polarized, your scanner will work best when the scanner is also in a vertical position. You will see this effect most frequently on weaker signals.
 

kb2vxa

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Hi guys,

Just to add an important point, dead spots can be caused by multi path reception, (one signal direct, the other reflected off an object in the area) the "two signals" can cancel each other out. Moving the receiving antenna to another location, sometimes just a few inches in the case of UHF and SHF can make quite a difference. Laying the antenna over can do the same thing sometimes, it's impossible to tell the difference between phase cancellation and cross polarization loss without sophisticated equipment and measurements.

Still the rule is keeping the antenna vertical, you won't notice cross polarization loss on strong signals but it will kill the weak ones. It's typically 20dB on VHF and gets much worse as the frequency goes up.
 

DiGiTaLD

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Aug 10, 2005
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I notice that holding the antenna horizontal cancels out most of the Nextel interference I get on 800 MHz. The signal of the systems I'm monitoring are strong, but so is the interference!
 

n4voxgill

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Dec 15, 2000
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if you have a cell phoone you probably have noticed that you can turn in your chair and lose the signal. dead spots are very common with weak signals. strong signals and you ca probably take your antenna off and still pick them up.
 
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