Transcript of "An-Antenna-Is-A-Significant-Part-Of-Any-Two-Way-Ra56"
An antenna is a significant part of any two way radio system. No radio can outperform its antenna. Many times users have been able to improve the performance of a communications system merely by improving the antennas.dipole
The AM radio waves are below 2 MHz; these signals follow theEarth's curvature because they are reflected off theatmosphere Therefore AM radio signals in low-noise environmentscan be received by radios that are way below the horizon hundredsof miles away Whereas two-way radios usually fall in the frequencyrange of 150MHz to 900MHz; these frequencies travel in straightlines Radio waves can be reflected, or bounce off surfaces so thestraight line between radios, may not always be so straight
Anyway as a general rule these waves cannot travel over thehorizon or behind solid obstacles Because of this reason, you haveto factor in antenna height as well for sending signals fartherAntenna gain is measured in decibels, or dB A 0 dB antenna(sometimes called a "unity" gain antenna), is an antenna with no gain
More gain on an antenna will, usually but not always, give you morerange Generally, to get more gain you need a bigger antenna Asimple "quarter wave" (0 dB, or unity gain) antenna for VHF is about18 inches long A 3 dB antenna for the same frequency would beabout 4 feet long, while a 5 dB antenna is maybe 8 feet
For UHF, a quarter wave is six inches, and a 5 dB about 2 feetLower the frequency, longer the antenna If you're using the 3inch stubbies on a UHF portable, you might see a difference going tothe six inch rubber duck Theoretically the longer antenna is better
Directional antennas achieve much of their gain by rejecting pick-upfrom certain areas, such as the sides and rear in the case of a logperiodic (the typical shark fin is an example of a log periodicantenna) A higher level signal helps improve the signal to noise ratioby overcoming the noise induced in an antenna cable, but a signalthat is too high can cause problems at the receiver This is whyantenna amplifiers typically have jumper settings to apply the properamount of gain needed to compensate dipole for loss in a cable ofparticular type and length
There are other factors that affect the range of a two-way radio toosuch as weather, exact frequency used, and obstructions Theradio's power output has a factor too