Farmerik, I think the 1" would help, especially at the low end of the band. The coil diameter is important as well. The bigger the core, the looser the coil form can be, The extreme being the FSL, (ferrite sleeve loop).
I build a 7.5" diameter one of those as well as a Stacked Toroid Ferrite loop,- (30 140/43 toroid cores) and the coil coupling on those is very loose. Point being the high performance they exhibit has as much if not more to do with the coil diameter, (aperture) than the core proximity. What you can take away from this for your purpose, I don't know. I'm just speculating anyway.. What I know would help as well is using a good quality high count litz wire, like 250/46 or higher.count. Search mkmak222 litz wire on ebay. He's the best source I've found, Sorry for the rambling, Must be the Ambien
John?
