SWR meter internals

[Vaibhav Birit]

In an SWR meter(or Power meter) for HF, a transformer is used, with the coaxial cable acting as a single turn primary. Is it necessary to take off the shielding on that small portion of the cable where induction into the secondary is supposed to take place. otherwise how induction could take place?

 

[JimB]

In that type of SWR meter, it is best that the whole coax is passed through the toroid, BUT, only connect the braid of the coax at one end.
That way the braid makes a faraday screen and eliminates capacitive coupling between the coax centre and the winding on the toroid.

There must of course be a path for the screen of the coax feeder from transmitter to antenna, this is usually through the box containing the transformer/SWR meter.

JimB

 

[fredsm]

Yes.
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