My suggestion is to use the exact measurements and techniques described by K6SE, Earl Cunningham, for the Pennant transformer. You would expect around 950 uH from 10 turns spaced on the form, but actual samples are coming in at higher values. In a cross sample of almost 100 cores that I've tested, I've seen 2 distinct groups, but within the group, the tolerance is close. It seems that the batch to batch mix is variable though, and I will get that resolved soon. B. Ratio C. Primary initial impedance at the design lowest design freq.
Most cores are good way below the broadcast band.
As far as the Bev transformers are concerned, I continue to recommend the DC connected transmission line type over the others. Pennant Transformers according to Earl's design will be available shortly from Array Solutions. They are in a gasket cast aluminum box with a brass weep hole, and have a stainless steel rope eye, and gold plated binding posts. The coil is wrapped in fiberglass tape, and dipped in liquid polystyrene for stability. The Beverage transformers according to my own design will be there also, and have Cast aluminum housing, gasket sealed, groundrod clamp and aux.