# SWR Meter/Low Pass Filter Session 4

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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

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

SWR Meter Calibration Forward Calibration Balance Assumed…see manual
Several Methods Possible Make a look up table based on LTSPICE Make a look up table based on precision measurements Use 1 or 2 but create a graph to read SWR Use analog meters like the conventional cross meter type 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

SWR Meter Calibration R4=R3 =0 Power Input [W] 10 2.8 2.7 9 2.6 8 2.5
VF/VR [V] (LTSPICE) VE3TLY VF (Measured) Daiwa meter to set power 10 2.8 2.7 9 2.6 8 2.5 7 2.3 6 2.1 5 1.9 1.8 4 1.7 3 1.4 2 1.1 1 0.71 0.8 0.5 0.41 0.2 R4=R3 =0

SWR Meter Calibration Example Calculation VF = 2.7 VR= 0.50
Power Input [W] VF/VR [V] (LTSPICE) VE3TLY VF (Measured) Daiwa meter to set power 10 2.8 2.7 9 2.6 8 2.5 7 2.3 6 2.1 5 1.9 1.8 4 1.7 3 1.4 2 1.1 1 0.71 0.8 0.5 0.41 0.2 Example Calculation VF = 2.7 VR= 0.50 PF = 10 PR = .50 Then x = SQRT(PR/PF) = and SWR = 1.57 R4=R3 =0

Low Pass Filter 14 MHz Application
9 Turns 8 Turns Output INPUT

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

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

Low Pass Filter Measurements AIM 4170

Low Pass Filter Measurements HP Analyzer VE3ZRK

Simulation 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

Construction 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

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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