A
Anonymous
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I came across a reel of Litz wire which had the same equivalent cross section as the wire I use on a standard Goldquest coil and thought it would be interesting to do a comparison. The standard wire is single strand 0.25mm Kynar insulated. In other words, standard wire wrap wire. The coils were wound on the same day, using the same winding jig and the same method of shielding. I even swapped the coils on to the same length of coax. Inductance was the same to within two or three microhenries and both coils measured 6 ohms. I will say at this point that the Goldquest uses a higher resistance coil than most other PI designs, hence the thinner than normal wire.
The standard winding was plugged into the Goldquest first and the damping adjusted to give a flat response, which had fully recovered by 8uS. The Litz coil was swapped in and it was noticed that the damping was not now optimum. In fact, a lower resistance was required to return to the flat response. Having done this, the Litz could be seen to recover marginally slower, but there was very little in it, and sampling at 10uS still had plenty in hand.
This shows that the Litz coil has a little more self capacitance, which must be due to the thinner cotton insulation on the wire relative to the Kynar on the single strand. Detection performance of the two coils was identical.
The conclusion is, that, as far as the Goldquest is concerned, there is absolutely no advantage in using Litz wire in the coil.
Eric.
The standard winding was plugged into the Goldquest first and the damping adjusted to give a flat response, which had fully recovered by 8uS. The Litz coil was swapped in and it was noticed that the damping was not now optimum. In fact, a lower resistance was required to return to the flat response. Having done this, the Litz could be seen to recover marginally slower, but there was very little in it, and sampling at 10uS still had plenty in hand.
This shows that the Litz coil has a little more self capacitance, which must be due to the thinner cotton insulation on the wire relative to the Kynar on the single strand. Detection performance of the two coils was identical.
The conclusion is, that, as far as the Goldquest is concerned, there is absolutely no advantage in using Litz wire in the coil.
Eric.