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So I'm trying to reverse engineer the schematic for an Avair AV-200CN SWR bridge. Two toroid coils, used for sensing, are mounted on a shunt, so that the shunt goes through the center of the coils.

I'm not 100% sure how to draw such an arrangement on a schematic. Was initially thinking of drawing it as a transformer with two secondaries, since the shunt acts as a one-turn primary, but I'm not sure if there's a better way to draw it, since I'd like to minimize the amount of thinking needed to understand the schematic.

Here's the picture of the circuit:
Photo of circuit showing metal shunt threaded through two toroidal coils

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    \$\begingroup\$ "Shunt" usually means a low value resistor (<< 1 Ω) so that current through it creates a small, measurable voltage drop. In this case the voltage drop is not required as it is a transformer circuit. It is just a "conductor". \$\endgroup\$ – Transistor Jun 25 '17 at 22:27
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Here's one example where a strict adherence to schematic symbols can cause confusion - that single-turn "winding" can easily be done wrong. Many SWR schematics do a pictorial representation of a toroid that helps make clear the single-turn nature (one wire through the toroid's centre) of the current transformer:

Current transformer toroid schematic

Perhaps not clear is the phasing of the multi-turn winding of the transformer - the "dot" convention is easy to get wrong. It might be easier to leave the labels of input connector and output connector off until it is built. Then discover which direction gives a null with a dummy load in place.

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  • \$\begingroup\$ In the end, I decided to take this route. I simply don't need to think as much when I see this type of schematic. \$\endgroup\$ – AndrejaKo Jun 28 '17 at 15:50
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Draw it as a transformer where one of the windings has got a single turn.

enter image description here
T301 and T302 are the cores with sensing windings. W303 is the shunt.

This schematic should translate well into the PCB layout. The toroids aren't rigidly connected attached to each-other, or to the shunt. So, in this schematic they are separate components. If you need even more flexibility during layout, the shunt could be represented by two separate pads, instead of one component with two pads.

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It is not a shunt. It is considered a one turn coil on the toroids. This is very typical for SWR meters.

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