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Antenna SWR

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Antenna SWR                          *  James Road (Street) 16,   Fairleads,   Benoni.        Tel: 011-969-3301,   Fax: 086-545-6004,  Cell: 082-264-4180  *   Bi-Comm Radios > Tech Info > Antenna SWR YOU AND YOUR MOBILE ANTENNA Three main components subsume a typical Two-Way Radio installation. They are: your transceiver, an antenna, and the coaxial subscription that connect the antenna to the transceiver. It is important that all three pieces are installed correctly to requite the weightier possible range and reliable performance. We hope this pamphlet will be helpful for you to realize the maximum performance from your radio installation.   ANTENNA For several reasons, it is untellable to exactly PRE-TUNE an antenna at the factory. A unstipulated range of tuning is washed-up which may suffice, but for weightier performance, an antenna should be tuned without it is installed. Most antennas have some form of tuning capability. Usually, this involves the whip section sliding into a coil, spring, or metal section. Failing this, the manufacturer will normally supply the antenna tuned to the lowest advertised frequency.  This allows for trimming the “active radiating element”, antenna rod or whip, by adjusting or wearing it to the correct resonant length. This works on the same principal as a tuning fork, used by piano tuners. The shorter the fork, the higher the frequency it will radiate, and visa versa.  When the antenna is adjusted for the centre frequency of operation, waterworks 20 for CB, they should perform well from the lowest to the highest frequency. An untuned antenna robs you of liaison loftiness and could cause, without a period, substantial deterioration of performance, or plane destruction of an RF output transistor. We cannot stress unbearable the importance of tuning your antenna. The measure of an antenna's performance is tabbed its "SWR" (Standing Wave Ratio).   "COAX" CABLE Coaxial subscription is used in scrutinizingly all radio installations. This subscription transfers the power from the transceiver to the antenna. The output impedance of a two way radio transceiver is designed to be 50-ohm.Liaisonantennas are designed with an input impedance of 50-ohm. Therefore, RG-58 or RG-213 coaxial subscription is well suited considering it moreover has 50-ohm impedance, and will perfectly match the transceiver to the antenna. The resonating frequency of the antenna is very important, considering a mistuned antenna can disrupt the system balance. If this wastefulness is disrupted, standing waves are generated on the coaxial cable, which results in a loss of power delivered by the transceiver.   UNDERSTANDING SWR (Standing Wave Ratio) With the transceiver having a 50-ohm output, and a properly tuned antenna a 50-ohm input, by using a 50-ohm subscription (such as RG-58 or RG-213), all the power (ignoring coaxial subscription losses), from the transceiver will be transferred via the coaxial subscription and radiated by the antenna.  Under these conditions, the SWR (standing wave ratio) of the antenna system would be 1:1. This condition seldom exists and standing waves are set up on the cable. A upper SWR robs you of power and range. While 1:1 is not unchangingly possible to attain, you should tune your antenna system so the SWR does not exceed 1.5:1 or at maximum 2:1. Here are some examples of the power losses for various SWR ratios: SWR  Power Losses 1:1  0   1.3:1  2% 1.5:1  3% 1.7:1  6% 2:1  11% 3:1  25% 4:1  38% 5:1  48% 6:1  55% 10:1  70%  TUNING YOUR ANTENNA For optimum performance, use an SWR meter to tune the antenna. However, since these meters are rhadamanthine increasingly and increasingly plush now a days, not everyone may want to invest in such an instrument. If possible, infringe one. If you are unable to infringe one, you can use the RF output meter on your transceiver if it is equipped with one, as a GUIDE to antenna tuning. While it is not very accurate, it is often largest than no tuning at all.Unchanginglytune your antenna in an unshut area. Wires, metal and copper tubing if nearby can stupefy the tuning. Never tune an antenna inside a garage, under a metal car port, next to a metal truck, etc.    A. USING YOUR TRANSCEIVER OUTPUT METER AS A TUNING GUIDE WARNING: DO NOT CUT THE WHIP USING THE "POWER OUTPUT METER TUNING METHOD". YOU MUST USE A SWR METER TO ACCURATELY DETERMINE THE SWR.Withoutinstalling your antenna system, place the whip halfway into its receptacle and turn your transceiver to its centre frequency, waterworks 20 on CB. (NB! For AM/SSB radios, switch the radio to AM). Depress the switch, moreover tabbed the “Press To Talk or PTT”, on the transceiver microphone, and make note of the reading on your RF output meter. Loosen the willowy whip section and lengthen the antenna 1 to 2 cm. If the antenna has no adjustment, use a piece of solder or thin copper wire to increase the whip length by wrapping it virtually the top of the whip.Thendepress the PTT, if the reading is the same or lower protract increasing the length until the LOWEST reading is obtained on the RF meter. If the reading is higher, shorten the whip 1 to 2 cm at a time until the LOWEST reading is obtained on the RF meter. I do not suggest wearing the whip unless you have a proper ‘SWR’ meter at hand. THE LOWEST READING.  Your RF output meter is a voltage sensing device. It is installed in the RF output spin and senses the voltage near the antenna terminal. In a perfectly tuned system all the voltage is transferred from the output transistor and passed to the antenna. As an example, let's use the icon 10. If there is SWR on the line, the forward voltage is 10 and a reverse voltage appears (let's say it's 2). The meter spin now sees 20 and shows a higher reading. You can see that considering of the way most RF output meters work, the LOWER your RF output meter reads the largest the tuning of the antenna. Of course, if the meter reads less than 1/2 scale, it may indicate a problem in your set and should be checked.  Similarly, an extremely upper reading may indicate a problem in your antenna. An RF output meter can tell you much.....especially if you know how to use it.   B. TUNING YOUR ANTENNA WITH AN SWR METER Using an SWR meter is the most well-judged way to tune an antenna. Connect the SWR meter as tropical as possible to the when of the transceiver. Use a double male-connector or a very short piece of RG-58 with connectors on each end. Place the willowy whip halfway into its receptacle. Turn your transceiver to its centre frequency, waterworks 20 on CB. (NB! For AM/SSB radios, switch the radio to AM). Measure the SWR pursuit the instructions supplied with the meter. Make a note of the meter reading. Loosen the willowy whip section and lengthen the antenna 1 to 2 cm. If the antenna has no adjustment, use a piece of solder or thin copper wire to increase the whip length by wrapping it virtually the top of the whip. Key the transmitter and read the SWR again. If the SWR is lower, protract the process lengthening the whip once increasingly until the lowest reading is obtained. If the SWR is higher, lower the whip 1 cm at a time, until the lowest SWR is obtained. Note, if the reading continues falling but you have reached as far lanugo as you can go with the whip, the whip may be too long. To verify this, switch the transceiver to the lowest frequency (Channel 1 on CB) and measure the SWR. Next, switch the transceiver to its highest frequency (Channel 40 on CB) and measure the SWR. IF THE SWR WAS LOWEST ON THE LOWEST FREQUENCY, AND HIGHEST ON THE HIGHEST FREQUENCY, THE WHIP SECTION IS TOO LONG. Carefully cut 1/2 cm at a time from the whip section and re-measure the SWR on the lowest, middle and highest frequency (Channels 1, 20, and 40 on CB). If the SWR is still lower on the low frequency compared to the upper frequency,  protract trimming the whip a little at a time. If the SWR is the same on both lowest and highest frequency, the antenna has reached its optimum length wideness the frequencies used. DO NOT GET OVERANXIOUS. YOU CANNOT REPLACE A SECTION ONCE IT IS CUT OFF. If you are unsure, first lengthen the whip a little with a piece of solder, the re-check the SWR reading.  Every six months or so, recheck the SWR. Car washes, rod grime, and chemicals can stupefy the mechanical connections of an antenna and corrode them. This corrosion can rationalization poor electrical connections and lead to upper SWR. The correction of this problem is usually workaday by cleaning of the metal connection parts with a wire brush.    HELPFUL HINTS 1.UpperSWR robs you of range and puts a strain on the radio's final output transistor.     ALWAYS TUNE A NEW ANTENNA. 2. Never tune your antenna in a sealed zone (garage, under a metal car port, etc.) as incorrect tuning may result. 3. MAKE SURE ALL MECHANICAL CONNECTIONS ARE CLEAN & TIGHT. 4. DO NOT SMASH OR SHARPLY BEND THE COAX CABLE – it should not be wrench with a radius sharper than six times its own diameter. Sharp bends will effect the characteristics of  the coaxial cable.               5. TIGHTEN YOUR PL-259 CONNECTOR OCCASIONALLY - road vibration has a tendency to loosen it which can rationalization output transistor failure. 6. PERIODICALLY (every 6 months) recheck your SWR. Corrosion and road grime may rob you of performance. 7. PERIODICALLY trammels your coax subscription for wear. A wrenched or loose wire could rationalization output transistor failure.  This information was produced to help you understand the installation and maintenance of your antenna and subscription feed system. Many field problems have been traced to problems such as the above. They lead to eventual failure of the RF output transistor or module in your transceiver which is plush to repair. Careful installation and maintenance can prevent these problems.  Return to top of page             * Home Products ◦  Alinco ◦  Antennae ◦  AnyTone ◦  Batteries & Chargers ◦  GME ◦  Icom ◦  Icom Land Mobile ◦  Icom Aircraft Radios ◦  Kenwood ◦  Kirisun ◦  Power Supplies ◦  Programming Cables ◦  QD Radios ◦  RTS Radios ◦  Vertex Standard ◦  Yaesu Used Radios Archives Electronic Components ◦  Potentiometer Tech Info ◦  Antenna SWR ◦  CW Abbreviations ◦  Electricity Theory ◦  Radio Frequencies ◦  Technical Resources ◦  Ten Codes Contact Us Meet the hairdo Site Map Privacy * Artikels ◦  Die Suidlanders