The magnet power supply needs to supply a constant current (1-2amps) and must be stable to within about 10ppm as this defines the resolution (I haven't actually worked out the required resolution yet, but I have to start somewhere). The magnet power supply is contains an op amp, so I need a power supply for that. Just finishing a +/- 15v power supply for it. (as I said before, I'm making as much as I can myself)

While I was doing it, it occurred to me that I could use a Maxwell coil. This uses three coils and provides an improved field homogeneity. The geometry is simple enough and has the added benefit that I can use my existing coils and because they will need to be placed further apart, it will give me a larger sample space. Also, if I have better homogeneity, I may not need golay coils to trim the field. Lastly, because I would be using three coils I should get a greater field strength which in turn increases the operating frequency and hence improve the signal to noise. (note. I guess it should be possible to create a four coil system, but I can't find any details about that, and the 'n coil' scheme requires greater engineering capability than I possess).

The only drawback is that I will need to wind a coil on a former that is apprx 120-130mm dia. Search as I may, I can find nothing that size. So what I will do is contact someone locally that has a 3D printer and see if they can make me one. If that works, I might get them to make the field gradient coils too.

I've also been looking at ultra low noise tuned amplifiers and it looks promising. I'm thinking of using a four wire 'twisted pair', which should have a lower characteristic impedance and hopefully reduce the noise figure. However, it is likely to make the matching network a bit fiddly.

It will take me a while to get the 3D former sorted, so in the meantime I will carry on with the 2 coil system in order to see what results I get with the tuned amp - just how bad the signal to noise is (might need to stick the whole thing in a Faraday cage).

So, by my next entry I should have acquired a basic resonance signal.

PS. If anybody can throw some light on field strength formula for 3 or 4 coil systems, I will be grateful.