One of the first things that I thought about when Gary first infected me with this disease was inductively coupling a major piece of ferrite, possibly tuned, to one of these little beauties. Gil Stacy has already done that, of course, and has uploaded a very nice article to Ultralight Radio Files area of DXer.ca. I'll be uploading an article to the files sometime in the next several hours that you might also find helpful
Almost 15 years ago, LWaver Bill Bowers and I set off on a quest to learn about Ferrite loops and to build the world's largest. We built a number of prototypes and smaller antennas before building "The Monster" that is about 4" in diameter and 16 feet long! It tilts and turns like other smaller ferrite loop antennas and is a wonder to behold. Bill spent a lifetime working professionally with very weak AC currents, magnetism and coaxial cables and was the prime mover on this project. I was project scribe, carpenter and provided a (then) strong back. Unfortunately, Bill moved to Houston from his home near me here in central Oklahoma and took The Monster with him. I still have a I" x 4' tuned/amplified loop antenna and, ahem, several pieces of "spare" ferrite. I'll be mating some of those to ultralights in the future. In the meantime, here are some of the things that we learned in our project: 1. The antenna of a ferrite loop is NOT the ferrite, but rather the coil wound around it. We found that the best coils were single layer coils from high wire count Litz wire, spaced off the ferrite about one wire diameter, with the turns spread apart about one wire diameter. The closer we came to those rules of thumb, the higher Q was the coil... Higher Q coils tune more sharply. However, a solid core hook-up wire is a great place to start and can be used to create a fine antenna. 2. The gain of the antenna is roughly proportional to the amount of ferrite. 3. The sharpness of the nulls is roughly proportional to the slenderness of the ferrite mass.... skinnier=sharper nulls. 4. It is possible to bind groups of smaller ferrite bars together to make a larger bar (we did that a lot.) HOWEVER, if the bars are placed end to end, the ends must be square, flat and very smooth. The goal is to have not even 1/100 inch between the ends.... NO GAP AT ALL. Bars may be bundled together in odd numbers... but the geometry must be very tight, like a wire cable in cross-section. You may bundle and place end to end to create a long, fat bar. If you do so, it is important to stagger the gap locations of the end to end bars. My own 4-footer is 3 bars in a triangular bundle. It is made of a dozen 1/2" diameter bars very carefully placed and wrapped with tape. Anyway, if you are thinking of moving into the Super Modified category of Ultralight Radios, Gil Stacy's article and mine will be of some interest, I think. I'll upload the Bowers-Bryant article sometime yet today and inform the group. It is a reprint from the Proceedings of Fine Tuning in 1994-95. John B. Stillwater, Oklahoma, USA Rcvrs: WiNRADiO 313e, Eton e1, NRD-535(kiwa-mods) Antennas: 700' NE/SW mini-Bev, Wellbrook Phased Array (pre-production version) _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
