Electronics > Beginners
How to attach an RCA connector to a chassis ?
macboy:
--- Quote from: jh15 on October 04, 2018, 04:30:00 am ---I agree the RCA is ok for home consumers. It has a 'how you doin' impedance for rf.
BNC failures come from video people a lot due to the different dimensions of 50 and 75 ohm connectors.
They may borrow cables from a bench instrument and plug into a pro monitor or verse visa.
I like hermaphrodite connectors such as on my GenRad stuff and Anderson powerpoles (for power, not impedance.)
--- End quote ---
75 and 50 ohm BNC are entirely safe to inter-mate because all contact dimensions are identical. The 75 ohm version simply does not have the dielectric within the mating area, which increases the impedance. The N type RF connectors do have different dimensions in the mating contacts and will be damaged by inter-mating. Many people assume the same for BNC, but it is not true.
I copied the following two sets of diagrams from one of Amphenol's spec sheets.
Richard Crowley:
Yes the common 50-ohm BNC connectors are mechanically interconnectable with the (more rare) 75-ohm version.
As @macboy says, the problem is that the center contact of the female 75-ohm BNC is essentially unsupported (without any dielectric mechanical support) and that makes it extremely vulnerable to any but the most careful connection. I have lost count of how many times a camera feed goes dead just before the program starts because some female 75-ohm BNC connector has gone intermittent because of deformed center-contact pin. Typically on the camera output or the switcher input.
jh15:
I stand corrected about the conductor dimensions.
I learned during ISF training that 75 and 50 ohm bnc connectors do not play nicely with gorillas or stage hands.
Now I need to know about n connector interfacing dimensions that I recently forgot. What's the story there? Something about the pin. I am worried not to damage my antenna analyzer.,
CJay:
--- Quote from: jh15 on October 07, 2018, 04:37:32 am ---I stand corrected about the conductor dimensions.
I learned during ISF training that 75 and 50 ohm bnc connectors do not play nicely with gorillas or stage hands.
Now I need to know about n connector interfacing dimensions that I recently forgot. What's the story there? Something about the pin. I am worried not to damage my antenna analyzer.,
--- End quote ---
Pin diameter of a 75R N connector is, I think, smaller than a 50R pin
langwadt:
--- Quote from: Richard Crowley on October 05, 2018, 06:27:42 pm ---Yes the common 50-ohm BNC connectors are mechanically interconnectable with the (more rare) 75-ohm version.
As @macboy says, the problem is that the center contact of the female 75-ohm BNC is essentially unsupported (without any dielectric mechanical support) and that makes it extremely vulnerable to any but the most careful connection. I have lost count of how many times a camera feed goes dead just before the program starts because some female 75-ohm BNC connector has gone intermittent because of deformed center-contact pin. Typically on the camera output or the switcher input.
--- End quote ---
I seems to remember reading that the 75 and 50 ohm BNCs became compatible by some standard that came out in the 70's,
the story that they aren't just keeps popping up
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