> OK, I guess it's about time I asked this. Is there someplace I can > find a reference on various connector types (plated or not, type of > plating) vs PIM/IMD/noise in duplex systems and/or in high RF > environments? I am looking at replacing my run of LDF5-50A and > wonder what type of connectors I *should* use.
Nickel-plated connectors, which are the most common type, are generally to be avoided. As I recall, nickel-plated connectors typically test 20 to 40 dB worse in two-tone PIM tests than silver plated. Gold over nickel is also not good (a lot of cheap hamfest connectors/adapters that are "gold plated" inside and out tend to be regular nickel/brass connectors with a thin gold plating). Gold-plated *center pins* are generally acceptable for small connectors (BNC, N, SMA, etc.). Connectors with larger center pins (EIA flange, 7/16 DIN, etc.) usually are silver-plated. Silver plating is better from a PIM and conductivity standpoint, but gold doesn't tarnish, hence the tradeoff. There are also some considerations regarding soldering to gold - it can partially dissolve in the molten solder resulting in the solder becoming more brittle. Huber+Suhner and others have other special platings that are low-PIM yet don't tarnish like silver (Sucoplate and Sucopro). Regular nickel-plated brass connectors are still an acceptable choice for test cables and other uses where they will see repeated connection/disconnection because the plating doesn't scratch, oxidize, or deteriorate as quickly do some of the other types, but for a repeater installation, stay away from nickel. http://www.ieee.li/pdf/essay/passive_imd.pdf http://www.imscs.com/passive-intermodulation.html http://www.tessco.com/yts/customerservice/techsupport/whitepapers/passive_in termod.html http://www.hubersuhner.ca/co-ca-us/hs-p-rf-con-kb-plat.pdf I don't pretend to be a metallurgist - somebody else may have better/additional information. This is just what I've heard/learned over the years through my own reading. As far as connectors on your LDF5, I still like the old-style connectors with the thread-in center pin (L5PNF would be N female, silver plated). They simply don't fail, unlike some of the newer connectors (RingFlare, OnePiece, etc.) which I have had problems with occasionally, especially on larger cable. Now, having said all of that, my real-world experience with single-frequency-pair repeaters (not combiners or other multicarrier systems) is that I've never had a PIM problem that I could attribute to connector plating. Any connector that I install is silver-plated (or H+S Succoplate), but I don't go to the trouble/expense of replacing non-silver-plated connectors on equipment like duplexers, radios, etc.. --- Jeff WN3A
