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# How do you determine the operating range of a antena? Answered

I found an antenna and was just wondering.

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## 7 Replies

Raven Destroyer (author)2011-05-02

i have a crappy antenna how i increase it's range?

Marsh (author)2009-11-25

Antennas are ALWAYS spec'd for specific operating ranges and nothing could be simpler than to compute the length. It's based on a formula....
468/F=L
Where:
F=Frequency in Megahertz
L=Length of Antenna in feet.

So for an antenna to operate on 101.1 MHz (right in the middle of the FM broadcast band) we would use....
468/101.1=4.62 feet or 55½"

This formula is for a ½ wave dipole antenna. This is an antenna where you have 2 conductors that are shaped into a "T" formation and one conductor is connected to each side of the antenna connection on the radio. Each of these conductors if half of the above mentioned 55½", or 27¾". The standard "T shaped" antenna that comes with a stereo is based on this design and you will notice that they are all the same length.
You may also use only one side of the antenna if you wish. If you do this, one side of the radio connection will usually be labeled with an Earth symbol (that looks something like this).....

/
/
------------
/      /       /
/      /       /

To use a single antenna like they do in a car, connect this side to a ground of some sort like a water pipe and the other to the 27¾" antenna (called a whip).
All of this is based on the scientific fact that all radio waves have a physical length. Hence terms heard on the shortwave bands like 10 meters, 20 meters, 80 meters. These are the physical wavelengths of the frequencies within those bands.

steveastrouk (author)2009-11-25

Sorry, I don't agree with you. I've NEVER seen an antenna spec that says "this is good for 20miles" or whatever. I'd appreciate a citation of somewhere it gives operating ranges.

Operating FREQUENCY of course, and your detailed explanation is true for simple dipole antennae

Steve

Dr.Bill (author)2010-01-16

And for 1/4 & 1/2 wave verticals.

Marsh (author)2009-11-25

The "operating range" of an antenna refers to the range of frequencies where it achieves optimal performance, not the physical distance it will transmit or receive a signal.
Physical distance a signal will travel can only be determined by knowing the Gain of the transmitting and receiving antennas, together with the transmitter power and receiver sensitivity. Other issues come into play also, but for starters those will do.
We must now turn to the OP to find out what they meant by the question.
What say ye, oldscool? Did you want to know frequency range or physical distance?

NachoMahma (author)2009-11-25

.  Antennae are not usually spec'ed by operating range (see steveastrouk's Nov 24, 2009. 11:42 PM comment plus frequency also enters the equation), but in dB.

steveastrouk (author)2009-11-24

Its hard to say. It depends on the design but mainly it depends on the transmit power, and the antenna and sensitivity of the receiver.

APPLICATIONS limit power, but radio amateurs can bounce a few watts around the world.

Steve