My time for a rant
Those gold plated BNC's are crimp types. Now whilst these are fine for fixed installs that do not see regular movement, they all, without fail in my experience, fail in the longer term.
It doesn't matter whether one crimps it correctly or not, the fundamental problem of the cable jacket creeping, be it cheap PVC, or something more exotic, eventually results in a loose connector and poor braid connection.
Go for a pressure-sleeve assembly for better long-term reliability, and then whinge at M/A Com / Greenpar and the like for buggering up all their new range in the pursuit of 'cheepness' as FZ would say.
The latest sockets we had, have a hollow centre pin, through which solder can flow - great - nice load of flux on the contact area unless you are really careful soldering
Now a crimp centre pin, with pressure sleeve outer termination would be good....
Take a great product, then mess it up in the name of progress
Andy.
Those gold plated BNC's are crimp types. Now whilst these are fine for fixed installs that do not see regular movement, they all, without fail in my experience, fail in the longer term.
It doesn't matter whether one crimps it correctly or not, the fundamental problem of the cable jacket creeping, be it cheap PVC, or something more exotic, eventually results in a loose connector and poor braid connection.
Go for a pressure-sleeve assembly for better long-term reliability, and then whinge at M/A Com / Greenpar and the like for buggering up all their new range in the pursuit of 'cheepness' as FZ would say.
The latest sockets we had, have a hollow centre pin, through which solder can flow - great - nice load of flux on the contact area unless you are really careful soldering
Now a crimp centre pin, with pressure sleeve outer termination would be good....
Take a great product, then mess it up in the name of progress
Andy.
Re: RE:STANDARDS.
Hey, come on... clearly no RCA plug / socket can be 75 ohm. The dimensions cannot allow it.
No doubt the connectors advertised are suitable for 75 ohm cable: that's it.
Speaking of which, who has compared the internal dimensions of 50 ohm and 75 ohm BNC's? Would it surprise you that those I've measured are the same? When you think about it, the discontinuity mismatch, even at the GHz they are rated at is trivial for the 10mm or so.
Puts to sleep a certain "old wives tail"....
Cheers,
fdegrove said:Hi,
Yeah....I remember how amazed we were when they announced this.
One more good reason to stick with vinyl a while longer I thought back than...
BTW, while doing a google on 75 Ohm RCA connectors I found quite a few, much to my surprise.
Has anyone measured these?
EXAMPLE.
FWIW, I suppose companies such as Linn,Wadia and who have you, buy in large quantities of the gold-plated BNC jobs from Taiwanese or Chinese factories.
Some day these should turn up on the market though.
Hey, why not?
May be fun after all...
Ciao,
Hey, come on... clearly no RCA plug / socket can be 75 ohm. The dimensions cannot allow it.
No doubt the connectors advertised are suitable for 75 ohm cable: that's it.
Speaking of which, who has compared the internal dimensions of 50 ohm and 75 ohm BNC's? Would it surprise you that those I've measured are the same? When you think about it, the discontinuity mismatch, even at the GHz they are rated at is trivial for the 10mm or so.
Puts to sleep a certain "old wives tail"....
Cheers,
Re: John
Andy,
The mating pin is the same diameter for 50 ohm and 75 ohm BNC. The difference is the crimp area at the back of the pin, as it has to accept thicker inner form 50 ohm cable.
More info at:
http://sosnick.uchicago.edu/BNC_50_75.html
Cheers,
ALW said:Measure the centre pin
Andy.
Andy,
The mating pin is the same diameter for 50 ohm and 75 ohm BNC. The difference is the crimp area at the back of the pin, as it has to accept thicker inner form 50 ohm cable.
More info at:
http://sosnick.uchicago.edu/BNC_50_75.html
Cheers,
Attention to details
The mating pin is not the same, as if you read carefully, you will note.
The pin diameter at the mating face has no effect upon interface impedance, since it's inside the socket receptacle.
The rear part of a 75R plug IS narrower, hence altering the interface impedance, and the 75R socket has a different external diameter to the pin, at the mating part, to maintain 75R.
If they're not, they're badly made. All the good manufacturers (i.e. non-audio) do it properly
Andy.
The mating pin is not the same, as if you read carefully, you will note.
The pin diameter at the mating face has no effect upon interface impedance, since it's inside the socket receptacle.
The rear part of a 75R plug IS narrower, hence altering the interface impedance, and the 75R socket has a different external diameter to the pin, at the mating part, to maintain 75R.
If they're not, they're badly made. All the good manufacturers (i.e. non-audio) do it properly
Andy.
Andy,
The part of the plug pin that one can see when an unmated assembled socket is in ones hand is the same diameter between impedances.
What you have brought me to appreciate, is that the recepticle in the socket is most probably a different diameter between impedances.
What this does not explain though, is why if the diameter is maintained for the correct impedance, it is necessary for the manufacurer to use differing dielectrics (ptfe / air) for the 2 impedances.
The reason the issue arose is that there is an old wives tale in the broadcast industry that inserting 50 ohm plugs into 75 ohm sockets is damaging. By measurement it is possible to refute this.
Cheers,
The part of the plug pin that one can see when an unmated assembled socket is in ones hand is the same diameter between impedances.
What you have brought me to appreciate, is that the recepticle in the socket is most probably a different diameter between impedances.
What this does not explain though, is why if the diameter is maintained for the correct impedance, it is necessary for the manufacurer to use differing dielectrics (ptfe / air) for the 2 impedances.
The reason the issue arose is that there is an old wives tale in the broadcast industry that inserting 50 ohm plugs into 75 ohm sockets is damaging. By measurement it is possible to refute this.
Cheers,
Here we go again......
Frank.......
OK, you win the prize, you actually found a gold BNC. Now all you have to do is find the crimper that the poor punter will have to shell out $$$ for. (Yeah, I know......pounds, but no "pound" key here......)
I would have thought you would have been smart enough not to trumpet that damn Canare connector. See my earlier challenge. For you, it is $2500.
75 ohm and 50 ohm BNCs are made to be interchangeable, at least over on this side of the pond. At one time, some connector makers had their own different dimensions, and they wee not compatible with anything else. They all got smart, and made them the same in the late 60s, or maybe early 70s. So, at one time, it was true that some were not compatible.
All they do is take out the Teflon around the center pin in the female, and the Teflon inside the barrel on the male to lower capacitance, and therefore raise the Z.
It had nothing to do with not knowing how to do it right, or for what application. They all also make 75 ohm TNC, and Type N connectors, which do have the proper dimensions.
Maybe I can scan a male connector...........
Jocko
Frank.......
OK, you win the prize, you actually found a gold BNC. Now all you have to do is find the crimper that the poor punter will have to shell out $$$ for. (Yeah, I know......pounds, but no "pound" key here......)
I would have thought you would have been smart enough not to trumpet that damn Canare connector. See my earlier challenge. For you, it is $2500.
75 ohm and 50 ohm BNCs are made to be interchangeable, at least over on this side of the pond. At one time, some connector makers had their own different dimensions, and they wee not compatible with anything else. They all got smart, and made them the same in the late 60s, or maybe early 70s. So, at one time, it was true that some were not compatible.
All they do is take out the Teflon around the center pin in the female, and the Teflon inside the barrel on the male to lower capacitance, and therefore raise the Z.
It had nothing to do with not knowing how to do it right, or for what application. They all also make 75 ohm TNC, and Type N connectors, which do have the proper dimensions.
Maybe I can scan a male connector...........
Jocko
Z is a function of diameter ratios, true; but dielectric constant enters into the eqaution. Most equations that we see are for air. You then have to factor in the dielectric constant.
It does not take much of a capacitance change to go from 50 to 75 if the dimensions are correct.
The rho difference is only 0.2 between the two. I see a rho of about half that amount just breaking the center conductor away from the shield for only a mm or two.
Jocko
It does not take much of a capacitance change to go from 50 to 75 if the dimensions are correct.
The rho difference is only 0.2 between the two. I see a rho of about half that amount just breaking the center conductor away from the shield for only a mm or two.
Jocko
75 ohm BNC connectors and coax cables are the staple of the entire video broadcast business. Analog and Digital video. Both present their own bandwidth problems.
The bandwidth of baseband High Definiiton Digital Television is 1.5 GIGAhertz. It is all connected using 75 ohm coax and BNCs. S/PDIF (and all of it's relatives) does not present a challenge compared to this.
I think the statements of "75 ohm BNCs connectors are rare" is increadibly misleading.
There are plenty of sources for these items. You need to look at video suppliers.
Aud_Mot
The bandwidth of baseband High Definiiton Digital Television is 1.5 GIGAhertz. It is all connected using 75 ohm coax and BNCs. S/PDIF (and all of it's relatives) does not present a challenge compared to this.
I think the statements of "75 ohm BNCs connectors are rare" is increadibly misleading.
There are plenty of sources for these items. You need to look at video suppliers.
Aud_Mot
Re: Re: THING IS YOU SEE...
Elso, others
AES/EBU uses XLR. Luckilly, its' impedance has been measured and used as a base for the impedance of that signal (110 ohms)
XLR ofcourse is not optimised for RF frequencies
SPDIF (the consumer standard) is using RCA from its' start. Sony forced Philips to do so, as Sony believed it was easier acepted as consumers where already using RCA
As the standardisation process was a matter of give and take between Sony and Philips, some compromises (ahum) where chosen. RCA for SPDIF is one .......
best regards
-
Elso Kwak said:
Hi Frank,
These RCA's are used because it is the AES/EBU norm. These guys chose the wrong standard and now there is no way back....
This is what the CS8412 datasheet mentions: "The connector for the consumer interface is a RCA phono plug (fixed socket described in Table IV of IEC 268-11)"
Elso, others
AES/EBU uses XLR. Luckilly, its' impedance has been measured and used as a base for the impedance of that signal (110 ohms)
XLR ofcourse is not optimised for RF frequencies
SPDIF (the consumer standard) is using RCA from its' start. Sony forced Philips to do so, as Sony believed it was easier acepted as consumers where already using RCA
As the standardisation process was a matter of give and take between Sony and Philips, some compromises (ahum) where chosen. RCA for SPDIF is one .......
best regards
-
I FIGURED...
Hi,
Yup, I thought Elso meant SP/DIFF anyway since this is the topic here,since he's a nice chap I didn't feel to slap him around the ears with it.
I see, these are the same people make publicity saying:
"Let's make things better" ??
Hey, at least this one was thinking and so far you're the only one spotting the catch.
The others still seem to be fast asleep so...moreover, signore, I figured out the whole thing on my own just by your hints or didn't I?
ROTFLMAO,
Hi,
Yup, I thought Elso meant SP/DIFF anyway since this is the topic here,since he's a nice chap I didn't feel to slap him around the ears with it.
I see, these are the same people make publicity saying:
"Let's make things better" ??
Hey, at least this one was thinking and so far you're the only one spotting the catch.
The others still seem to be fast asleep so...moreover, signore, I figured out the whole thing on my own just by your hints or didn't I?
ROTFLMAO,
Mr Aud-Mot,
Had you been reading a little more closely, you
would have noted that long ago I mentioned
that the vast majority of "75 Ohm BNCs" are
in fact 50 Ohm BNC connectors designed to mate
(crimp/clamp/clomp) to 75 Ohm coax. I have not
seen any HDTV or other "consumer" video that
has REAL 75 Ohm BNCs on it, but I will crawl behind
the display on my belly the next time I'm at
Best Buy just to verify.
Real 75 Ohm BNCs are indeed fairly rare.
Heck, I had an IBM monitor that had terrible
ghosting problems because the video cable
that came with it had the wrong impedance
in its coax.
And where do you get the idea that the bandwidth
of _BASEBAND_ HDTV is 1.5 GHz.? Preposterous!
Your average decent PC monitor these days has
far higher resolution and refresh rate than
HDTV and they don't have such BASEBAND bandwidth.
BTW, is that IXOS "gold plated" BNC real gold
plating (like >=50 microinches) or merely
gold flashed like so many "gold plated"
audiophile connectors?
Had you been reading a little more closely, you
would have noted that long ago I mentioned
that the vast majority of "75 Ohm BNCs" are
in fact 50 Ohm BNC connectors designed to mate
(crimp/clamp/clomp) to 75 Ohm coax. I have not
seen any HDTV or other "consumer" video that
has REAL 75 Ohm BNCs on it, but I will crawl behind
the display on my belly the next time I'm at
Best Buy just to verify.
Real 75 Ohm BNCs are indeed fairly rare.
Heck, I had an IBM monitor that had terrible
ghosting problems because the video cable
that came with it had the wrong impedance
in its coax.
And where do you get the idea that the bandwidth
of _BASEBAND_ HDTV is 1.5 GHz.? Preposterous!
Your average decent PC monitor these days has
far higher resolution and refresh rate than
HDTV and they don't have such BASEBAND bandwidth.
BTW, is that IXOS "gold plated" BNC real gold
plating (like >=50 microinches) or merely
gold flashed like so many "gold plated"
audiophile connectors?
Re: Re: Re: THING IS YOU SEE...
Yes the RCA connecter is SP/DIF standard. (short for Sony Philips Digital Interface ). What can I say, Sony and Philips on the wrong path.....
XLR is AES/EBU. I agree with Jocko that it is even worse.
The RCA connector is a big joke on itself. Later the TV/video industry followed with the F-type connector.. Hahahaha...
Guido,Guido Tent said:
Yes the RCA connecter is SP/DIF standard. (short for Sony Philips Digital Interface ). What can I say, Sony and Philips on the wrong path.....
XLR is AES/EBU. I agree with Jocko that it is even worse.
The RCA connector is a big joke on itself. Later the TV/video industry followed with the F-type connector.. Hahahaha...
Fwiw
The impedance of a coaxial cable ( and connector) is set by the formulae
Z= (138/ Eps.rel.) * log ( D/d)
where D= thicknessof dielelectric insulation, d=dia. inner conductor, Eps.rel=dielect. const. of insulation.
Aud_Mot is quite right in pointing to the professional video camp as the major user of 75 ohm BNCs these days. His statement of bandwidth is also mostly correct, as it is the design bandwidth for the signal distribution paths in larger video studios etc.,- although my catalogues mostly states 600-1000 MHz for digital and 200+ MHz for analog distribution. Bear in mind that most video work today is done on component signal basis, not composite video as by home entertainment, and the extensive use of routing and distribution is what sets this high demand for bandwidth.
Gold plated BNCs must be easily available, also stateside, but possibly not by RadioShack ( or Home depot for that matter )
Manufactures like Amphenol, Trompeter still makes them ....
I get a small catalog from Pasternack every year, but the catalog does not specify gold plated connectors for BNC.
OTOH, - I don't quite get this craze about gold plated BNCs,- most high quality BNCs are silver plated, and does an excellent job when kept clean, even way up in the GHz range....but keeping your impedances constant is imperative to maintaining a correct group delay of a digital signal. And it's been used with great reliability in the lab for ages, both for analog and digital work.
I do agree that the XLR used for AES/EBU is not really designed for RF work, but neither is the RJ45s used for 100MHZ and 1 GHZ networking,- but have youever tried sloppy mounting an RJ45 for high speed networking,- it immediately falls back to 10 MHZ,- if you're lucky!
The trick is of course that these systems are both designed for low level differential signalling.
Finally,- I totally agree that SP/DIF seems to be the result of a rather unhappy industrial compromise, but that's nothing new under the sun, is it.....??
A BNC connector or even AES/EBU would have been a much better way to go...
The impedance of a coaxial cable ( and connector) is set by the formulae
Z= (138/ Eps.rel.) * log ( D/d)
where D= thicknessof dielelectric insulation, d=dia. inner conductor, Eps.rel=dielect. const. of insulation.
Aud_Mot is quite right in pointing to the professional video camp as the major user of 75 ohm BNCs these days. His statement of bandwidth is also mostly correct, as it is the design bandwidth for the signal distribution paths in larger video studios etc.,- although my catalogues mostly states 600-1000 MHz for digital and 200+ MHz for analog distribution. Bear in mind that most video work today is done on component signal basis, not composite video as by home entertainment, and the extensive use of routing and distribution is what sets this high demand for bandwidth.
Gold plated BNCs must be easily available, also stateside, but possibly not by RadioShack ( or Home depot for that matter
)Manufactures like Amphenol, Trompeter still makes them ....
I get a small catalog from Pasternack every year, but the catalog does not specify gold plated connectors for BNC.
OTOH, - I don't quite get this craze about gold plated BNCs,- most high quality BNCs are silver plated, and does an excellent job when kept clean, even way up in the GHz range....but keeping your impedances constant is imperative to maintaining a correct group delay of a digital signal. And it's been used with great reliability in the lab for ages, both for analog and digital work.
I do agree that the XLR used for AES/EBU is not really designed for RF work, but neither is the RJ45s used for 100MHZ and 1 GHZ networking,- but have youever tried sloppy mounting an RJ45 for high speed networking,- it immediately falls back to 10 MHZ,- if you're lucky!
The trick is of course that these systems are both designed for low level differential signalling.
Finally,- I totally agree that SP/DIF seems to be the result of a rather unhappy industrial compromise, but that's nothing new under the sun, is it.....??
A BNC connector or even AES/EBU would have been a much better way to go...
Did he really say that???
Signoro Tent stated that XLRs are 110 ohms, or so. Rather than take someone else's word, I measured a connector pair.
It is close to being 100 ohms, but an accurate measurement is tricky, as "it is not optimised for RF". There is fringing where the wire pair is split to go to the pins. The reflections that occur are of a significant level and will cause jitter problems.
Jocko
Signoro Tent stated that XLRs are 110 ohms, or so. Rather than take someone else's word, I measured a connector pair.
It is close to being 100 ohms, but an accurate measurement is tricky, as "it is not optimised for RF". There is fringing where the wire pair is split to go to the pins. The reflections that occur are of a significant level and will cause jitter problems.
Jocko
I have had success in gold plating and as far as the danger, you are probably thinking of cyanide based chemicals. However, there are other gold electroplating solutions that rely on mild acids to work, and are far more safe.
I also have silver plating chemicals and they are kind of scary, because they are cyanide based. I didn't get good results with it and also am a little apprehensive to try again.
Stu
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