Saturday, 17 January 2015

10" coil too low

I had hoped that my next coil would come out around the 250uH mark, but it seems this was not to be. The same technique was used as the huge 50cm beast to connect the turns, care being taken this time to select wires that were on the same 'face' of the coil as each other

The completed coil, including the screen connection, looks very good

But sadly, when tested, comes out a bit too low! It seems the ideal target is somewhere between 250 - 300uH. The higher inductance better for the receive circuit, the lower better for the transmit circuit!

Although perhaps not ideal, this coil is at least convenient for testing. I'll use this to try out the Surf PI, at least until I have some suitable cable for a closer inductance coil! Knowing that this one at 10" is a bit low, and the 50cm one is way over, I should be able to estimate a coil diameter that will give the holy grail 300uH!

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