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Thread: SWR Meter question

  1. #1

    Default SWR Meter question

    So I have this simple stripline SWR meter. If I understand from research that SWR = volt(f)+volt(r)/volt(f)-volt(r)

    So if my volt(f) is 5 and my volt(r) is 1.3 then my swr is 1.7:1

    Since itís the same circuit for forward as it is for reverse then if I reverse the coax on the meter the reading should be the same right?

    What I am seeing is that I set the forward calibration to 3 on the meter and I flip the coax and the switch (fwd/ref switch) I now get about a 4 on the meter. If my test is a true test of function then obviously my meter is way off accurate.

    So an I horribly mistaken on my tests and itís fine or is it a case if you get what you get for $15

    Brad


    Sent from my iPhone using Tapatalk

  2. #2

    Default

    The diode detector in the meter circuit is directional.

  3. #3

    Default

    Maybe you could do that if you were using a Volts and an AMPS Meter, but not a SWR meter..

    Tempstar is correct - look at the schematic -even my old MFJ 949's used a 1n270 detection diode..

    https://www.mfjenterprises.com/suppo...uctid=MFJ-949E

    You are asking a Generic question and you didn't even give the make / model number of the SWR meter...

  4. #4

    Default

    He is quite right in his comment. A meter with a forward and reverse switch should read exactly the same if you flip the switch and reverse in and out. The strip sensing method of 'sniffing' the RF should be symmetrical. The trouble is that many meters also contain trimmers to adjust the response so the meters appear to be more sensitive at the bottom end, making the response non-linear in a beneficial way. If the full scale reading is 100W then good VSWR readings will be a tiny movement. Cheaper meters sacrifice accuracy and make antenna adjustments easier. Reversing these ones changes the readings quite a lot.

  5. #5

    Default

    With identical diodes and trimmer adjustment it would be possible to make the meter read the same both ways.

    73,

    Nandu.

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