Thursday, January 5, 2012

Some Antenna Do’s

There are some things that one should avoid when planning or working an antenna installation.

-  Keep away from power lines.  They are deadly.  There is any number of ways to come into contact with power lines and your chances of survival are slim to none.  This also means masts or towers that can fall over onto power lines once erected or during erection.
-  Always wear gloves when handling rope, cable, coax, antenna wire, etc, while putting up antenna installations.  A small slip of any of these can remove quickly remove everything to the bone and beyond.
-  Always wear a qualified safety harness every time you set foot on a tower and hard hats all around.
-  RF exposure must be taken into account.  It is a FCC rule.  The Amateur Radio RF Safety Calculator on DX-Zone’s website will help you perform the RF exposure study required by the FCC. 

LOCATION CONSIDERATIONS (To make it easier on me, this posting will not consider HF antennas.)
-  Generally speaking the higher you can put an antenna the better.  This is especially true for VHF/UHF antennas. 
-  Keep your antenna away from trees.  Trees will absorb RF signals both inbound and outbound again especially at VHF/UHF frequencies.
-  Whenever possible get above buildings.  Metal buildings will act like a reflector to inbound and out bound signals.  Metal siding and roofs, electrical wiring, metal window screens, metal Venetian blinds, E glass windows, etc, can cause problems with your signal.  You may experience a signal that is coming in strong, but the voice is so garbled you cannot understand it.  This is usually caused by something called multipath.  The inbound signal is bouncing off a metal surface somewhere between you and the transmitted signal.  It can often be solved by moving the antenna on one end or the other by as little as a quarter wave length.
- Orient your antenna with the radiating element in a vertical plane for FM work and in the horizontal plane for SSB and CW.  These are conventions use by ham radio and other radio services.  Tilting the antenna or wrong orientation will cause your signal to drop off in strength.  This is easy to forget when using a hand-i-talky.


NOTES:  All of these considerations apply to mobile antennas and portable operations.
                       See Antennas in the topic list and read “Using the Amateur Radio RF Safety Calculator”

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