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MEASUREMENTS

MEASUREMENTS. Antenna Measurements. Feedline and Load. SWR. S tanding W ave R atio Z load = Z o (Feedline characteristic impedance) ? If Z load = Z line , SWR = 1, else SWR > 1 SWR > 1:1 Due to Reflections from load, and Constructive and Destructive interference. “Standing Waves”.

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MEASUREMENTS

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  1. MEASUREMENTS

  2. Antenna Measurements

  3. Feedline and Load

  4. SWR • Standing Wave Ratio • Zload = Zo (Feedline characteristic impedance)? • If Zload = Zline , SWR = 1, else SWR > 1 • SWR > 1:1 Due to Reflections from load, and Constructive and Destructive interference “Standing Waves”

  5. Acceptable “SWR”? • 1:1 is perfect match • 2:1 is fairly good, but transmitter may start to reduce power output • 4:1 is poor, may stress parts, some power lost as HEAT in feedline, and transmitter will reduce power output

  6. Antenna Tuner and SWR Meter Measures Impedance Ratio Impedance Transformer

  7. SWR Meter Forward, adjust Sensitivity to “SET” (Transmitting) Reverse, read SWR (Transmitting)

  8. Antenna Tuner Action Note that “SWR Meter”, when used with Antenna Tuner, Doesn’t actually measure SWR on feedline Measures Impedance Ratio Between Zload and design Z = 50 Ohms “SWR =1:1” means Zload = 50 Ohms “Impedance Transformer” High SWR on feedline is still present and is usually OK Low SWR Here Transmitter is Happy, because it can deliver power to antenna system!

  9. Dummy Load Use to prevent Radiation when Testing Transmitter (instead of using Antenna)

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