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Installing coax connectors is relatively easy, however, it takes some practice.
Once you understand the basic procedures and have installed several PL259s, you will be on your way to becoming an 'expert connector installer'... Try these tips:
The Antenna circuit is just what it is ... An electrical circuit having characteristics to perform a function: Radiate RF energy when transmitting and absorb RF energy when receiving.
The Antenna circuit starts from the radio antenna connector (typically SO-239) to the antenna radiating elements, and can sometimes include the ground. When taking RF measurements (Standing Wave Ratio (SWR) and power) of your antenna, make sure you include all devices between the radio and the antenna such as the tuner, coax switches, and power amplifier, if installed. Don't forget, any device in the antenna circuit can effect the performance. The coax is part of the antenna circuit, so place extra emphasis on the coax AND its connectors when diagnosing antenna problems.
Read as much as you can about antennas. Try not to be discouraged if you find the reading to be over your head. Just start from the basics and ask questions from those who have successfully installed antennas.
One last thought... Determining the performance of an antenna is mostly relative when requesting the signal strength from another station. Antenna height, direction, radio propagation, and other factors affect antenna performance. Don't panic if you get a weak signal report from someone on the air. Find your antenna direction pattern, get the propagation for the frequency you are operating and get two or three reports from stations on different days. This will give you a good idea of how well your antenna is performing.
Coax loss can come from several things.
Moisture can get into coax causing the impedance to change. Moisture can also cause a short in the coax. The most common area where moisture can enter the coax is the coax connector. Sealing and taping the coax connector will help eliminate moisture from entering the coax.
An impedance mismatch can cause high SWR. Most amateur radio transmitters use a tank circuit impedance of 50 Ohms. For an antenna circuit to be properly tuned, it must match the transmitter impedance. A 50 ohm coax can be used for antennas that have an impedence of 40 to 60 ohms. A Balun (BALance/UNbalance) is used when connecting a Unbalanced coax cable to a Balanced antenna. Also, a balun or other type transformer that changes the impedance should be used on antennas that are other than 40 to 60 ohms.
Coax has loss! For short lengths of coax or for frequencies up to 30 MHz., loss is not too much of a problem. However, for Very High frequencies and above (50 Mhz. and above), runs of about 50 feet or more require low loss coax. Use a coax chart to find the transmission line loss per frequency and length.
Remember, high SWR means that there is a mismatch between the transmitter and antenna which causes power loss. However, coax line loss can not be measured by the SWR meter. You can have a flat SWR and have high loss because of either a high loss coax or a long run of coax, or both.
Too many coax connectors can also contribute to loss in your antenna system. PL259/SO239 connectors at UH and VH frequencies causes an impedance 'bump' which will cause an RF loss. BNC and N connectors are physically made to pass RF with very little resistance. For VHF/UHF operation, use N or BNC connectors if you need to 'extend' the coax.
If you have questions about Coax, Connectors, or other antenna supplies, please E-mail Uncle Joe.
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