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Published bySeth Lane Modified over 2 years ago

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SWR Meter/Low Pass Filter Session 4 SWR Meter Calibration Methods Discussed Finish SWR meter Start the Low Pass Filter Project

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SWR Meter Calibration SWR = [1+x]/[1-x] where x = Sqrt(P R /P F ) P R is the Forward Power P F is the Reverse Power We get P R and P F from the SWR meter

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SWR Meter Calibration Forward Calibration Balance Assumed…see manual Several Methods Possible 1.Make a look up table based on LTSPICE 2.Make a look up table based on precision measurements 3.Use 1 or 2 but create a graph to read SWR 4.Use analog meters like the conventional cross meter type 5.Use 1.5:1, 2:1 and 3:1 loads….very easy Read TCA March/April 2012 on SWR/Power Meters,VA3DDN QST April 2012 on Power Meters..the old basic meter

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SWR Meter Calibration Power Input [W] VF/VR [V] (LTSPICE) VE3TLY VF (Measured) Daiwa meter to set power R4=R3 =0

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SWR Meter Calibration Power Input [W] VF/VR [V] (LTSPICE) VE3TLY VF (Measured) Daiwa meter to set power R4=R3 =0 Example Calculation V F = 2.7 V R = 0.50 P F = 10 P R =.50 Then x = SQRT(P R /P F ) = 0.22 and SWR = 1.57

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Low Pass Filter 14 MHz Application T50-6 INPUT Output 9 Turns8 Turns

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Low Pass Filter 14 MHz Application Second and Third Harmonics Attenuated 45 dB

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Low Pass Filter ELSIE 14 MHz Application Second and Third Harmonics Attenuated > 40 dB

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Low Pass Filter Measurements AIM 4170

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Low Pass Filter Measurements HP Analyzer VE3ZRK

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Simulation 1.Put the supplied filter file into a folder on your computer 2. The file name is VE3KLCauerLowPass14mHzappVersion2.LCT 3. Open up the Elsie Program 4. Click Retrieve Old Design then open the file above 5. Click Schematic if not opened to start the process 6. Click Plot 7. Now experiment with the filter plot options and other windows

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Construction 1.Build each resonator and test with AIM 4170 Put capacitors close to the coils. See my models Leave lots of wire on inductors as before Rewind coils if necessary: 9 turns and 8 turns # 26 Gauge wire. I have lots of wire and toroids 2. Now label the input/output ports of the circuit board with supplied label 3. Wire the series parts first, then solder the parallel capacitors 4. Measure the SWR with the AIM meter

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Summary Can improve SWR meter by using matched diodes and transformers. Use 1% resistors. Good example of Ferrites Low Pass Filter good for filtering square waves Good example of Powdered Iron (High Q)

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