On Sat, Oct 23, 2021 at 06:35 PM, peter bunge wrote:
Why the Cobalt alloy?? It may as well be solid nickel or nickel plated copper.?
Perhaps it has to do with the temperature coefficient.
I see there are at least a few hams here, so undoubtedly you will know about radio repeaters, and the duplexers (filters) they use to allow simultaneous transmission and reception with only one antenna.? The tuning rod in duplexer cavities is made of invar, which is 36% nickel and 64% iron.? Invar has a low thermal coefficient of expansion, and is used so the frequency of the cavity won't drift as the temperature changes.? I know of mountaintop repeater sites locally where the ambient temperature can vary at least 50° C. with the seasons.? There are other similar alloys such as Inovco and FeNiCo that also have low coefficient of expansion.? HP says the electrode is nickel plated cobalt (Fe 54%, Co 17%, Ni 29%).? I'd guess thermal coefficient of expansion is one of the reasons for this choice, perhaps combined with corrosion resistance, thermal conductivity, electrical resistivity, and HP-only-knows what else.
Jim Allyn - N7JA