An SWR Thingy


100w 50 ohm resistors, overkill i know. HAHA. For such a simple circuit that an swr bridge is, i really do not understand its operation. Yeah i get the diode rectifies AC to DC and we twiddle the knobs till we get an output voltage that suits the meters or ADC we are using. Its the bit above that which does not make much sense to me, like how does the transformer separate out forward and reverse powers. That is beyond my level of comprehension. And it seems none of my books know either and seem to take it on faith that it works.


4 thoughts on “An SWR Thingy

  1. It’s really 2 transformers though. One on the output, sampling the forward power and one on the input, sampling the reflected power. Each has its own path and rectification diode.

  2. While technically 2 transformers in this case Gerry, it does not have to be and the whole process can be done with a single coupler. That said, one thing that I do know is that we are not separately sampling forward and reverse power at different ports, (something that can be easily demonstrated with a simple experiment and a couple of resistors, because there is no refection without a transmission line) but rather we are sampling the complex current and voltage at the point of insertion. To do that we have a current transformer and a voltage transformer and from then on, and this is where my head explodes, its all math and how a couple of resistors and diodes performs that math boggles my mind.

    I am a visual person, and understand circuits by visualizing what they do in my mind and I just cant for the life of me visualize the math.

    1. Its my own work, but I stopped sharing my board designs because of the abuse I was getting for not offering them the kind of support they though they were owed and for not using the parts they had, rather than the ones I had. I can help you learn how to design a pcb board though, an swr meter is a simple thing and a good first project. Just hit me up in email.

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