Hi Chuck, some early 75R BNC designs did use a smaller diameter center contact. The 75R male can make intermittent contact when used with a worn or top of limit 50R female. The 75R female can be damaged for use with the small contact male if used with a 50R or large contact 75R male. The do exist, but are pretty rare. A lot got changed out as faulty. I've not seen one on any modern (last 20 years) equipment. Robert G8RPI.
________________________________ From: Chuck Harris <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Sent: Friday, 22 February 2013, 6:15 Subject: Re: [time-nuts] altinex switches In general, no, they are not. The connector pins for modern 75ohm BNC's are exactly the same part as for modern 50 ohm BNC's. The BNC gets the higher impedance inside of the connection area by removing most of the inner dielectric. The real problem child, in general, is the female 75 ohm N connector, vs the male 50 ohm N connector. In this case, the connector has no dielectric in the mating area, so in order to keep the impedance constant, it has to have a smaller diameter center conductor on the 75 ohm variant. If you attempt to mate a 50 ohm male N connector with a 75 ohm female N connector, you will split out the female center socket pin. Legend has it that there were some variations of the 75 ohm BNC that don't work with 50 ohm variety.... I can't speak to whether or not that is true, only that in my 40 years in the business, I have never seen one where there was a problem. -Chuck Harris paul swed wrote: > Good point Bob the 75 ohms are smaller in diameter. I use 75 ohm connectors. > The 50 into a 75 hole spreads the jack. > Regards > Paul > WB8TSL > > On Thu, Feb 21, 2013 at 4:16 PM, Bob Camp <[email protected]> wrote: > >> Hi >> >> Be careful with the BNC connectors on those switches. 75 ohm BNC's aren't >> the same as 50 ohm connectors. The inner contact is different enough that >> they don't always play well together. >> >> Bob _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
