G'day, > If you use type 77 material (u=2000), use enough beads to cover 1 foot of > the coax,. The Amidon part # for type 77 beads is FB-77-1024, which has > an I.D. of 0.5" and a length of 0.825", so it would take about 15 of > these beads. ARRL Antenna Book, 17th edition, p26-20 supports this number. Regards, Mike VP8NO