antenna height

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tbharper

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what would be a good height to put antenna ? i have 25 foot in the air know is that good enough?? picking up 40 miles away with if
 

Audiodave1

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Hello,
Other factors aside... like your elevation above what you are trying to hear, The target stations height, power, distence and the band your antenna is optimized for....

I have found that you really hit a point of diminishing returns around 30'.
15' of added height likely will not make the difference in receiving a station you currently do not get.

Look at upgrading your coax or getting a band specific antenna before going higher.

We all always want to hear "just a little further"

Dave
 

kc8zdf

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It kinda depends on how far you want to here or if you are just listing to the counties around you. I have a 2 meter sleeve antenna up 35 feet and the radioshack uhf and vhf antenna up there as well and have no problem hereing 70 to 100 miles away so the question to you is what are you mostly listing to and what do you want to here.

p.s. 25 feet is a good start.
 

kb2vxa

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Hi all,

"go as high as you can."

OK, height is might but like the man said there comes the point of diminishing returns. Where that point is becomes a wild card without careful and complex calculations based on system gain (must include HAAT calcs, not the antenna gain alone) vs. transmission line loss vs. frequency. In other words a professional site survey is in order which leaves those outside the RF communications industry with a best guess situation.

A best case scenario would be perhaps sitting at the base of a 100' tower with a high gain antenna and Times Microwave LMR-800 or hard line but we should be so fortunate. Using that as a template you can take a well informed guess that with a good antenna with good coax mounted as high as practical you'll come out on top. Then being on top of the highest mountain in the area is better. If you live at the bottom of a hole you're SOL no matter what you do, thankfully we seldom encounter the worst case scenario.

Some install a good antenna up high and try tio cheap it out in the coax department, a real shot in the foot. Don't be one of those, use your noodle and THINK before you reach for the sky. THEN reach for the sky, this is a holdup! (;->)
 

timjude

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Someone explain this,i live 35 miles from a federal pen if i put my antenna up over 15 ft i can't even hear the control ch..i can lay it on the ground and recieve it perfect i live in a mountian terrain but i am not messing with length of cable or anything,,but over 15 ft and all signal is lost from the big sandy federal pen?so hight may not always be better
 
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kb2vxa

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Hi Tim and all,

There are "dead spots" so try moving the antenna a bit laterally. There are factors that determine how the waves arrive at the antenna, sometimes they arrive over multiple paths (multipath) and cancell each other out. Moving the antenna changes the phase relationships between them, changes the factors that determine reception. Just raising the antenna doesn't make sense unless you raised it "just right" into the path of another signal from the same transmitter so they cancelled each other.

In a sense you're right about higher isn't necissarily better but there are SO many factors to consider, no wonder you're confused. The key to it all is "mountain(ous) terrain", the perfect environment for reflections that result in multipath effects.

BTW, a narrow beam antenna helps reduce or eliminate multipath reception by "zeroing in" on the desired signal while rejecting the others. Anyone who has tried to receive TV in the mountains can tell you that aiming is critical to eliminate "ghost" signals and get a clear picture.
 
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