Error in sentence ... should say "over time a 50 ohm N male connector can damage a 75 ohm female N connector and a 75 ohm N male may not make reliable contact with the 50 ohm female."
Too early in the morning. Jack K8ZOA On 9/17/2012 6:10 AM, Jack Smith wrote: > There seems to be confusion over 50/75 ohm connector mechanical > compatibility. > > 50 and 75 ohm N connectors are not mechanically compatible as the center > pins are different diameter--50 ohm has larger pin diameter. Over time, > a 50 ohm N male connector can damage the 50 ohm female N and a 75 ohm N > male may not make reliable contact with the 75 ohm female N. > > However, everything I can find in terms of published dimensions, > specifications and measured diameters says that BNC pins are of > identical diameter in 50 and 75 ohm variants. The difference in > impedance seems to be handled in the dielectric dimensions and material. > > Many HP 75 ohm BNC connectors, for example, have no plastic dielectric > at all in the female version--the center socket fingers have nothing > supporting them but air. > > It may be that in "ye olde days" of the early 1940's when the BNC was > invented pin diameters differed, but if that was the case then, it seems > to have vanished in the last few decades. > > Jack K8ZOA > > > On 9/17/2012 4:19 AM, David Cutter wrote: >> Wrong use of 75/50 ohm cables is a cause of unreliability on scopes: they're >> made for 75ohm connectors and if you plug in a 50ohm plug is will eventually >> splay the centre contact and cause intermittency. >> >> David >> G3UNA >> >> Subject: Re: [Elecraft] [K3] [P3] IF Out / IF In Cable >> >> >>> Yes, the cable impedance does not matter but the connectors do. The >>> 75-ohm cable probably has 75-ohm BNC plugs, which as I recall have a >>> smaller pin. They might not make reliable connections with the 50-ohm >>> sockets on the K3 and P3. >>> >>> Go ahead and try it, but if the connections seem flakey you should get a >>> real 50-ohm cable. >>> >>> Alan N1AL >>> >>> >>> On Sat, 2012-09-15 at 17:21 -0700, Jim Brown wrote: >>>> On 9/15/2012 5:01 PM, Vic K2VCO wrote: >>>>> Just try one of the non-50-ohm cables and see if it works >>>> Cable impedance absolutely does not matter for such a short run at the >>>> IF frequency. >>>> >>>> 73, Jim K9YC >>>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
