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

2. 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

3. 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

4. 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

5. 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

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

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

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

9. Low Pass Filter Measurements AIM 4170

10. Low Pass Filter Measurements HP Analyzer VE3ZRK

11. 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

12. 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

13. 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)