EW Coil design changes.

In researching the latest information on the EW design changes over time I found this from Thierry in an older post...

You'll obtain that by applying the same modifications which Bob Moog developed during the transition from the old EM design (which had a smaller pitch range and worse linearity) to the newer Etherwave design: Using a 40cm long and 10mm thick pitch antenna and only 3 of these 10mH coils (Hammond 1535G). The oscillator's tank circuit should be formed by a 3.3nF silver Mica capacitor in parallel with 94uH (a fixed inductor and a variable inductor of 47uH each in series). 

I am in the processing of finalizing the design updates, sourcing parts and laying out a PCB based on the EW design published in the HotRodEtherwave document.  In order to determine the types of components I've been working mostly off of the original EM parts list specifications.  I did follow the specs for the Hammond coils, TOKO coils, etc. but am struggling most with the various types of capacitors called for.  I'm happy to follow your suggestion on the mica capacitors in the three oscillator tank circuits.

I would, however, like to understand more about the 4->to->3 coil change in both the pitch and volume antenna circuits.    Does this also apply to the volume side as well since that also changed to three coils.  In other words, can I use three 5mH coils in place of L7-L10 coils?  Or did L14 change as well and I should be using 3 coils of some other value for the pitch antenna?   

The "original" EM-Design had a variable 68uH inductor in the tank circuit and 4 linearization coils (2 x 5mH + 2 x 2.5mH).

The newer improved design uses a variable 47uH inductor in series with a 22uH fixed inductor for the tank circuit and 3 linearization coils (1 x 5mH + 2 x 2.5mH).

The detection circuitry (D1 etc.) around the 2.5mH coil closest to the oscillator remains the same.

When precisely tuned, the newer circuit variant gives a beautiful and smooth volume response with a field height of about 30cm / 12".

Thanks for the clarification on the volume side!  

On a side note,  as I was assembling the various capacitors from the original EM spec I happened to find a high resolution pic of an EW board from dated 8/11/2011.  One thing that surprised me was that all of the capacitors originally spec'd as tantalums in the EM article  appeared to all be aluminum electrolytic on the production board pic.

I am following your advise to use mica for the C1,5 and 14's and I was planning on following the EM article's specs for the others (ceramic, NPO ceramic, and polyester) just not sure about the tantulum's....

Back in the golden days of the EM development, tantalums weren't a always as long-term stable as the should have been and often a source of stability problems. There was a gap between theory and practice. Today there is no more reason to worry about that.