Driving Stock Tachometer

[smalcol]

I have a stock tachometer that was driven by the coil signal originally. I'm using a Dakota Digital SGI-8 to convert it to the right signal after an engine swap. Frustratingly, it doesn't seem to be outputting the correct signal for my tach. It has signal from megasquirt, seems to be syncing according to the status light, but the tach doesn't move.

So, I've found a diagram showing a relay wired to 12V positive as a "pull-up" between the tach output signal and the tach. Using a relay seems less than ideal, what other inductive component would I look for at radio shack for example?

Thanks,
Seth

[DaveEFI]

An inductor of approx 100mH should do it. But it might be easier to simply remove the coil from a relay?