Measuring inductance on sovereign coil

[samd12]

I am attempting to take L readings from various sovereign coils and am have an issue with the receive side. I know that it should be somewhere around 400uH but my meter is jumping all over the place, from 180-320. The Tx side is solid for all the coils. Is there something that needs to be done to help stabilize the reading on the rx side? Any ideas?
I am using a BK 879B meter.
Thanks

[plumabob]

No can do without dismantling the coil. The RX runs through a pre-amp buried inside the coil. There is no way to get to both leads unless the coil is opened up.

Bob

[samd12]

Appreciate the feedback plumabob. I was trying to get to that inside a bad coil I have but it has been slow going trying to cut through the epoxy without damaging anything. So if that is the case can people share some L and R readings for their sovereign coils (tx and rx) they have built. I have seen L readings of 1.014Mh (tx) and .401Mz (rx). What type of coil will this make (hot, stable?) Also where should the R falll? I was planning on starting with 29 gauge magnet wire for the rx and 19 or 20 gauge for the tx. The R will of course affect that. I am looking at building a larger coil say in the 18x14. First I want to build a tiny coil for testing though.

[plumabob]

Your TX and RX numbers are safe. If you use the AD797 pre-amp you can bump up the RX to about .465uH. but leave the TX alone. Factory tornado coils I have tested were at .440uH but some can be slightly lower. 29awg is good for your RX. With your 18 inch coil you may need to use 19-20 awg. I usaully am at 21-22awg but my coils are smaller. I have built 18 inch sovereign coils but they did not perform well and are way too cumbersome for me. I have had the best success with 13x11 and 14x12 inch coils.

Bob

[samd12]

Great info, I appreciate the feedback. When you say the 18" didn't perform well did you not get depth or did you get a lot of interference?

[plumabob]

Depth was no better then the smaller coils I mentioned. Didn't see any advantage lugging around the extra size and weight. And forget about using it in the water.

Bob