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BNC connectors 75 Ohm versus 50 Ohm?
I recently was able to use a crimp on tool for F connectors for RG-6 quad
shield coax. To make sure everyone understands, I am in Israel, and RG-6 quad shield coax is cheap and easy to find. Any other coax is almost impossible to find. Pl-259 connectors, called "UHF" connectors here are rare items. I can get them locally, but I have to special order them and they are expensive. Since I can not see them before I order them, I am as likely to get nickle plated ones with phenolic insulation as I am to get any other kind, and once ordered are not returnable. BNC to PL-259 adaptors, are easy to get, and can be ordered from a reliable local souce for a relatively small price. The same with N to PL-259. Looking around at the crimp-on F connectors before I ordered them, I found that you can get crimp on BNC connectors for RG-6 quad shield coax. Here's my questions, Note when I say crimp-on, I mean the ones that crimp from the rear, like commerical F connectors, not the ones that crimp around the plug. I have never been able to get any of them to "fit right": 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? 2. Are there crimp on 50 ohm BNC plugs which will work with RG6 quad shield? I know there are variations, but most are similar in size. 3. Are there crimp on N connectors that would fit the RG6 quad shield coax? More likely due to the size a crimp on center element that screws into the plug body? 4. Are there crimp on PL-259 connectors? Thanks in advance, Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
"Geoffrey S. Mendelson" wrote in
: I recently was able to use a crimp on tool for F connectors for RG-6 quad shield coax. To make sure everyone understands, I am in Israel, and RG-6 quad shield coax is cheap and easy to find. Any other coax is almost impossible to find. Pl-259 connectors, called "UHF" connectors here are rare items. I can get them locally, but I have to special order them and they are expensive. Since I can not see them before I order them, I am as likely to get nickle plated ones with phenolic insulation as I am to get any other kind, and once ordered are not returnable. BNC to PL-259 adaptors, are easy to get, and can be ordered from a reliable local souce for a relatively small price. The same with N to PL-259. Looking around at the crimp-on F connectors before I ordered them, I found that you can get crimp on BNC connectors for RG-6 quad shield coax. Here's my questions, Note when I say crimp-on, I mean the ones that crimp from the rear, like commerical F connectors, not the ones that crimp around the plug. I have never been able to get any of them to "fit right": 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? There is such a thing as a 75 ohm BNC connector, but you are almost certainly looking at 50 ohm connectors designed for use on 75 ohm cable. My recollection is that the 75 ohm connectors are incompatible with the 50 ohm connectors, and in some combinations will spread the female inner part. 2. Are there crimp on 50 ohm BNC plugs which will work with RG6 quad shield? I know there are variations, but most are similar in size. Yes, see http://www.vk1od.net/transmissionline/RG6/index.htm . 3. Are there crimp on N connectors that would fit the RG6 quad shield coax? I haven't seen any. I use BNC compression connectors on the RG6, then BNC/N adapters to connect to the antenna N connector. Works fine, all waterproof. More likely due to the size a crimp on center element that screws into the plug body? 4. Are there crimp on PL-259 connectors? Yes. They have most of the disadvantages of the PL-259. If you are of the view that everything that comes out of China, leave now. I buy N, BNC, UHF, etc connectors that are of Chinese original that are economical and excellent quality. But... you have to be picky, price is not a good indicator of quality. There is also a prejudice against RG6. Again, quality varies, and you need to inspect carefully and test product that you might use. Owen Thanks in advance, Geoff. |
BNC connectors 75 Ohm versus 50 Ohm?
Owen Duffy wrote:
There is such a thing as a 75 ohm BNC connector, but you are almost certainly looking at 50 ohm connectors designed for use on 75 ohm cable. My recollection is that the 75 ohm connectors are incompatible with the 50 ohm connectors, and in some combinations will spread the female inner part. Thanks, The ad I saw said they were 75 ohm. If they really are 50 ohm connectors for 75 ohm cable, so much the better. Without buying them, I have no way to tell, and it's awfully expensive to buy one or two. Shipping from the US to here runs between $20 (USPS) and $50 (FEDEX/DHL/UPS) for anything. I was going to buy $10 worth of soldering iron tips from Farnell, and they wanted a flat rate of $35 to ship them. :-( Yes, see http://www.vk1od.net/transmissionline/RG6/index.htm . I haven't seen any. I use BNC compression connectors on the RG6, then BNC/N adapters to connect to the antenna N connector. Works fine, all waterproof. Wonderful, thanks. I buy N, BNC, UHF, etc connectors that are of Chinese original that are economical and excellent quality. But... you have to be picky, price is not a good indicator of quality. URLs??? Please. There is also a prejudice against RG6. Again, quality varies, and you need to inspect carefully and test product that you might use. As in everything in life. :-) Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
On Sat, 5 Jun 2010 21:49:32 +0000 (UTC), "Geoffrey S. Mendelson"
wrote: I recently was able to use a crimp on tool for F connectors for RG-6 quad shield coax. Hopefully, it was a "push-on" tool and connector http://www.arrisistore.com/digicon/Digicon-F-Connector-Installation-Guide.pdf not the piece of junk with the small crimped ring. To make sure everyone understands, I am in Israel, and RG-6 quad shield coax is cheap and easy to find. There's quality RG-6a/u and junk. On the left coast of the USA, we have both in copious quantities. I obtain mine directly from a satellite DTV install company, so the quality is more towards quality than junk. Pl-259 connectors, called "UHF" connectors here are rare items. Be thankful. I find them to be a necessary evil as most ham radios require them. Meanwhile, commercial radios are moving away from UHF and toward other connectors, such as Type-N, BNC, TNC, Mini-UHF, and SMA. However, Comerica base antennas remain UHF or Type-N. BNC to PL-259 adaptors, are easy to get, and can be ordered from a reliable local souce for a relatively small price. The same with N to PL-259. That's what I do. Most of my cables are NOT terminated with UHF connectors. If I need to go to UHF, I use an adapter. Looking around at the crimp-on F connectors before I ordered them, I found that you can get crimp on BNC connectors for RG-6 quad shield coax. Yes, they work. I use quite a bit of RG-6a/u and prefer to have everything terminated by the same connector, which is the CATV standard F connector. If I need BNC, I use an adapter. Here's my questions, Note when I say crimp-on, I mean the ones that crimp from the rear, like commerical F connectors, not the ones that crimp around the plug. I have never been able to get any of them to "fit right": Agreed. The good ones are "push on" F connectors. 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? There are such things as real 75 ohm BNC plugs and jacks. They're easy to recognize because they lack the PTFE dielectric. The 75 ohm connectors will mate properly with the 50 ohm connectors. There is little risk of VSWR problems from using 50 ohm connectors on RG-6a/u. http://www.qsl.net/n9zia/wireless/75_ohm_hardline.html Basically, any small loss from VSWR is compensated by the lower loss per meter of RG-6a/u as compared to RG-58a/u. Methinks you're safe using all 50 ohm connectors.[1] 2. Are there crimp on 50 ohm BNC plugs which will work with RG6 quad shield? I know there are variations, but most are similar in size. They're nearly identical in dimensions. The 50 ohm variety have some manner of PTFE dielectric. The 75 ohm variety use a plastic disk and no dielectric. http://www.amphenolconnex.com/products/bnc.asp "50 ohm and 75 ohm connectors are intermateable to ensure non-destructive mating" The catch is that there's no guarantee that this is true between different manufacturers. I've blundered across mutations and variations that are NOT interchangeable. 3. Are there crimp on N connectors that would fit the RG6 quad shield coax? More likely due to the size a crimp on center element that screws into the plug body? Probably, but I wouldn't use one. Just terminate in an F connector, and use an F to N adapter. The price will probably be the same or less. However, if you must go direct, any N connector that will fit RG-59a/u will usually work with RG-6a/u. The problem is that depending on the number of shields in the RG-6a/u, the outer diameter will vary, making the diameter of the crimp ring an issue. Doing this is risky and may result in a non-fitting connector. I would use an adapter, which will always work. 4. Are there crimp on PL-259 connectors? Also probably, but again, methinks you're better off with an F connector and an adapter. [1] I just counted 7 assorted coaxial cables going between my roof and various RF devices in my house. All but one are 75 ohm RG-6a/u. Some are double shielded, while others are quad shielded. The connectors are slightly different. All the HF and VHF/UHF antennas use 75 ohm coax. The one 50 ohm LMR-400 run is for the 900MHz antenna. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
BNC connectors 75 Ohm versus 50 Ohm?
Jeff Liebermann wrote:
Hopefully, it was a "push-on" tool and connector http://www.arrisistore.com/digicon/Digicon-F-Connector-Installation-Guide.pdf not the piece of junk with the small crimped ring. Thanks, Yes, but mine looks more like a nut cracker, however it works the same way. Be thankful. I find them to be a necessary evil as most ham radios require them. Meanwhile, commercial radios are moving away from UHF and toward other connectors, such as Type-N, BNC, TNC, Mini-UHF, and SMA. However, Comerica base antennas remain UHF or Type-N. Me too. Since all of the ham radios I have were either brought from the US in 1996 when I moved here, or even older ones brought here, they use Pl-259's or in one case an RCA jack (Drake SP-R4) for the antenna. TV sets still use the Belling-Lee plugs (called PAL connectors in the US) and so do VCRs. Everything else uses F connectors (cable TV, Satellite TV) although RF outputs to TV sets have gone the way of the VCR. DVB is just starting here and the tuners use Belling-Lee connectors. F to Belling-Lee adaptors are common here, and even in the US, where Radio Shack sells them. That's what I do. Most of my cables are NOT terminated with UHF connectors. If I need to go to UHF, I use an adapter. They are also hard to get and expensive. Yes, they work. I use quite a bit of RG-6a/u and prefer to have everything terminated by the same connector, which is the CATV standard F connector. If I need BNC, I use an adapter. OK, So where do you get your adaptors? Agreed. The good ones are "push on" F connectors. I gave up about 10 years ago and used the cheap screw on ones because they gave me a better fit than the crimp "around" types. The push on ones are a lot better. There are such things as real 75 ohm BNC plugs and jacks. They're easy to recognize because they lack the PTFE dielectric. The 75 ohm connectors will mate properly with the 50 ohm connectors. There is little risk of VSWR problems from using 50 ohm connectors on RG-6a/u. ok. http://www.qsl.net/n9zia/wireless/75_ohm_hardline.html Basically, any small loss from VSWR is compensated by the lower loss per meter of RG-6a/u as compared to RG-58a/u. Methinks you're safe using all 50 ohm connectors.[1] Good, thanks. [1] I just counted 7 assorted coaxial cables going between my roof and various RF devices in my house. All but one are 75 ohm RG-6a/u. Some are double shielded, while others are quad shielded. The connectors are slightly different. All the HF and VHF/UHF antennas use 75 ohm coax. The one 50 ohm LMR-400 run is for the 900MHz antenna. That's not an issue, 900mHz is not a ham band here, and 1.gHz too short range to consider using. I think there is one 1.2gHz repeater in the country, and I can't hit the co-located 2m repeater anyway. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
On Sun, 6 Jun 2010 01:19:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote: That's what I do. Most of my cables are NOT terminated with UHF connectors. If I need to go to UHF, I use an adapter. They are also hard to get and expensive. My guess(tm) is that they are less expensive than oddities such as an N-connector for RG-6a/u. They also have the advantage of being reusable. When you destroy your coax cable, just unscrew the adapters and use a new F connector. I sometimes have to make my own adapters. It's not because the adapter is unavailable or hard to find. It's because the accumulated length of the connectors and adapters can get quite long. There are also mechanical considerations, where an N to SMA adapter will surely break at the SMA when the heavy cable is bent. For SMA and Mini-UHF adapters, I sometimes use short pigtails to act as a strain relief. OK, So where do you get your adaptors? It varies. Once a year, I got to one local hamfest and stock up. I like to see the connectors to make sure they're not junk. I typically buy about $150 worth every year. Much of it disappears during Field Day. The problem is that most of this stuff is nickel plated. Nickel is fine for systems which are not potentially affected by intermodulation issues. Therefore, I'll use them at home, Field Day, other hams stations, and my mobile. I won't use them for repeaters, mountain top sites, and microwave links. http://www.amphenolrf.com/simple/PIM%20Paper.pdf http://www.repeater-builder.com/antenna/pdf/andrew-braid-over-foil-imd.pdf http://www.repeater-builder.com/antenna/pdf/recommended-coax-and-connectors-for-iden.pdf For repeaters, I use silver plated connectors, when I can get them. Gold plating is an option, but under the gold is a layer of nickel, which worries me a little (most of the RF flows on the surface). Tin plate also works. I buy most of my connectors from RF Industries: http://www.rfcoaxconnectors.com Their mix is really bizarre. They offer Nickel, Tin, Silver and Gold plating, but not in every type of connector. For example, F adapters are available only in Nickel or Gold, while UHF connector are only available in Nickel and Silver. Trying to avoid dissimilar metals is difficult. Other sources are eBay, various online dealers, the local electronics sto http://www.santacruzelectronics.com the local cable company, and the local DTV satellite installation company. The latter are my best sources of RG-6a/u and F connectors. I once obtained a free bucket full of filthy connectors that someone had left in the rain. Rather than clean them, they went to me, instead of the recyclers. There were literally hundreds of F connectors in the bucket. If you're working on the HF and VHF bands, you can probably just solder two connectors together to make an adapter. I have a bunch of BNC to UHF adapter I made this way. The BNC panel jack fits nicely into the PL-259 connector. The losses are not signifigant, even at microwave (2.4GHz) frequencies: http://802.11junk.com/jeffl/antennas/connector-loss/ I've done 8 ft chains of adapters with similar results. I don't know what to suggest. It sounds like getting someone in Europe to throw together a collection of connectors for you seems easier than importing them one at a time. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
BNC connectors 75 Ohm versus 50 Ohm?
Jeff Liebermann wrote:
My guess(tm) is that they are less expensive than oddities such as an N-connector for RG-6a/u. They also have the advantage of being reusable. When you destroy your coax cable, just unscrew the adapters and use a new F connector. I don't know. I've never seen them. OK, So where do you get your adaptors? It varies. Once a year, I got to one local hamfest and stock up. What's a hamfest? There are none here. http://www.rfcoaxconnectors.com I'll check them out. Their mix is really bizarre. They offer Nickel, Tin, Silver and Gold plating, but not in every type of connector. For example, F adapters are available only in Nickel or Gold, while UHF connector are only available in Nickel and Silver. Trying to avoid dissimilar metals is difficult. It's less important here. It rains about 14 days a year spread over 6 months. It rained for about 10 minutes in April, has looked like, but did not rain at all in May, and won't do it again until around November 1. http://www.santacruzelectronics.com I'll look at them too. I don't know what to suggest. It sounds like getting someone in Europe to throw together a collection of connectors for you seems easier than importing them one at a time. Actually that's a myth. While I am geographicaly closer, postage from the US is much cheaper than Europe. The only way shipping becomes cheaper if I were to load a container full on a ship. Then sending it from a Mediterranean port would be cheaper. Sending a single package from the US is cheaper and faster than anywhere else in the world with the usual, but not always exception of elsewhere in Israel. A single envelope, even one containing electronic components takes a week from a vendor to my door. A small box takes 2-3 and I have to go pick it up at the post office, even if they are the same cost and weight. The same with internet access, I can download files from the US at twice the speed from the UK, and 4-5 times that from continental Europe. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
"Geoffrey S. Mendelson" wrote in
: .... I buy N, BNC, UHF, etc connectors that are of Chinese original that are economical and excellent quality. But... you have to be picky, price is not a good indicator of quality. URLs??? Please. Jyebao is Taiwanese, not Chinese, and excellent quality. They have an agent in Israel. http://www.jyebao.com.tw/agent-u.htm Owen |
BNC connectors 75 Ohm versus 50 Ohm?
Owen Duffy wrote:
Jyebao is Taiwanese, not Chinese, and excellent quality. They have an agent in Israel. http://www.jyebao.com.tw/agent-u.htm Thanks. Interestingly enough, they have F-plugs to N jacks, (i.e. cables with F plugs on them to connect to a radio with an N jack) but not F plugs to PL-259(UHF) jacks. :-( 73, Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
Geoffrey S. Mendelson Inscribed thus:
I recently was able to use a crimp on tool for F connectors for RG-6 quad shield coax. To make sure everyone understands, I am in Israel, and RG-6 quad shield coax is cheap and easy to find. Any other coax is almost impossible to find. Pl-259 connectors, called "UHF" connectors here are rare items. I can get them locally, but I have to special order them and they are expensive. Since I can not see them before I order them, I am as likely to get nickle plated ones with phenolic insulation as I am to get any other kind, and once ordered are not returnable. BNC to PL-259 adaptors, are easy to get, and can be ordered from a reliable local souce for a relatively small price. The same with N to PL-259. Looking around at the crimp-on F connectors before I ordered them, I found that you can get crimp on BNC connectors for RG-6 quad shield coax. Here's my questions, Note when I say crimp-on, I mean the ones that crimp from the rear, like commerical F connectors, not the ones that crimp around the plug. I have never been able to get any of them to "fit right": 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? The short answer is yes ! A 75 ohm BNC plug is identical to a 50 ohm one, save that the male pin in a 75 ohm plug is smaller in diameter. The other way round, a 50 ohm BNC plug will damage a 75 ohm BNC socket. 2. Are there crimp on 50 ohm BNC plugs which will work with RG6 quad shield? Yes. But you have to be careful to get the right sleeve size and fitting them is not straightforward. I know there are variations, but most are similar in size. 3. Are there crimp on N connectors that would fit the RG6 quad shield coax? There should be, but I'm not certain. More likely due to the size a crimp on center element that screws into the plug body? 4. Are there crimp on PL-259 connectors? Yes ! Spit spit, yuk... I've always had trouble with these even used indoors. Usually the plating fails and gives intermittent connections Thanks in advance, Geoff. It might pay you to Google "Greenpar, Amphenol, Wellshow, Synergy" and the like. There is a lot of good data out there. -- Best Regards: Baron. |
BNC connectors 75 Ohm versus 50 Ohm?
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BNC connectors 75 Ohm versus 50 Ohm?
Hi Gaius,
Gaius Inscribed thus: In article , says... A 75 ohm BNC plug is identical to a 50 ohm one, save that the male pin in a 75 ohm plug is smaller in diameter. The other way round, a 50 ohm BNC plug will damage a 75 ohm BNC socket. Thats what I said... :-( Sorry. Not so. This is one of the most common urban myths in RF engineering. The pin diameters of BNCs are identical between 50 and 75R. (Measure them !!) I did... :-( The 50R and 75R connectors are mechanically compatible in BOTH directions. Don't take my word for it - check Amphenol's specifications: "Two distinct types of 75ohm BNCs are available, and both mate with each other and with 50ohm BNCs. " I did check that documentation... :-( I've been using 75R and 50R interchangeably for about thirty years, and I've had NO mating damage problems. (Mismatches don't worry me - HF only). I've probably used them for nearer 50 years, and had to replace damaged sockets because the bifurcated female pin had one side broken off. I am aware that some of the early plugs didn't have solidly captive pins and could move forward and cause damage. Greenpar package the plugs/sockets clearly marked 50 or 75 ohm. In all that time I've never bothered to check the specifications until now. Note - type N and type C connectors WILL be damaged if you try to mix 75R and 50R varieties. I suspect this is the source of the BNC myth. Having taken your words and accept that I'm wrong, I can only agree that you're right and it is a myth. Thanks for the insight. Also - some Chinese made BNCs are so badly made that they will damage other connectors - but this is a manufacturing tolerance issue. 73's -- Best Regards: Baron. |
BNC connectors 75 Ohm versus 50 Ohm?
On 6/5/2010 5:49 PM, Geoffrey S. Mendelson wrote:
I recently was able to use a crimp on tool for F connectors for RG-6 quad shield coax. To make sure everyone understands, I am in Israel, and RG-6 quad shield coax is cheap and easy to find. Any other coax is almost impossible to find. Pl-259 connectors, called "UHF" connectors here are rare items. I can get them locally, but I have to special order them and they are expensive. Since I can not see them before I order them, I am as likely to get nickle plated ones with phenolic insulation as I am to get any other kind, and once ordered are not returnable. BNC to PL-259 adaptors, are easy to get, and can be ordered from a reliable local souce for a relatively small price. The same with N to PL-259. Looking around at the crimp-on F connectors before I ordered them, I found that you can get crimp on BNC connectors for RG-6 quad shield coax. Here's my questions, Note when I say crimp-on, I mean the ones that crimp from the rear, like commerical F connectors, not the ones that crimp around the plug. I have never been able to get any of them to "fit right": 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? No the size of the center conductor pin is different between 75 and 50 ohm connectors and will either make bad contact or damage the socket. 2. Are there crimp on 50 ohm BNC plugs which will work with RG6 quad shield? I know there are variations, but most are similar in size. I don't think so, as there are large differences in the diameter of the 2 kinds of coax, both the diameter of the center conductor and the outside diameter of the coax. 3. Are there crimp on N connectors that would fit the RG6 quad shield coax? More likely due to the size a crimp on center element that screws into the plug body? I've never seen any and can't think of any commercial reason that anyone would make one. 4. Are there crimp on PL-259 connectors? Yes, I use them all the time. I like them much better than the solder on type. Most need the center pin soldered but the crimp connection to the shield is much easier and better done than when soldered Thanks in advance, Geoff. It's my experience that Teflon insulated PL259's are inferior to the phenolic insulation type. The PL259 is a non constant impedance connector that gains no benefit from Teflon insulation as to impedance. The ability of Teflon to hold the center pin in placed is greatly inferior to phenolic. One of the advertised benefits of Teflon is to withstand more heat, true but by the time the connector is heated enough to hurt the phenolic, the coax your trying to install is melted way. Nickel is harder to solder to than silver but the real problem with cheap PL259s is the inside diameter of the area with holes your supposed to solder through. I've measured a few and found them to uniformly to have a too big of an inside diameter. This means there is a larger gap between the metal of the connector and the shield than should be. This gap is hard to impossible to fill with solder and makes for poor heat transfer to the braid of the shield. Finding good connectors is much harder than it used to be as most high-end equipment manufacture are not using PL259s anymore and what hams can get are largely junk I'm afraid. I've seen on ham equipment SO239, the jack half, ones that were molded metal instead of machined brass. Those are hard to thread on a plug onto and are of a soft pot metal that cracks or binds. John Passaneau W3JXP |
BNC connectors 75 Ohm versus 50 Ohm?
John Passaneau wrote:
On 6/5/2010 5:49 PM, Geoffrey S. Mendelson wrote: 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? No the size of the center conductor pin is different between 75 and 50 ohm connectors and will either make bad contact or damage the socket. That's not necessarily true. I have some RG-59 cables with male 75 ohm BNC connectors that mate fine with 50 ohm connectors. The diameter of the 75 ohm connector center pin is the same diameter as 50 ohm connectors. The difference is that the dielectric surrounding the center pin of the 75 ohm connector is much thinner. And at the point where the pin enters the solid dielectric at the bottom, the 75 ohm pin doesn't step up in diameter. Others have said that there are some 75 ohm BNC connectors which won't interconnect without damage. But I do know there are some that mate with no problem. 50 ohm BNC connectors and adapters are very common. I suggest you get one and compare the center pin diameter with that of your 75 ohm connector. If it's the same, the two can interconnect without damage. I also have a lot of RG-59 cables with 50 ohm BNC connectors. That's probably more common, since 50 ohm connectors are much more common, and the connector choice won't make any practical difference in the vast majority of applications. Roy Lewallen, W7EL |
BNC connectors 75 Ohm versus 50 Ohm?
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BNC connectors 75 Ohm versus 50 Ohm?
On Sun, 06 Jun 2010 17:17:25 -0700, Roy Lewallen
wrote: I also have a lot of RG-59 cables with 50 ohm BNC connectors. That's probably more common, since 50 ohm connectors are much more common, and the connector choice won't make any practical difference in the vast majority of applications. Just a minor note, but coaxial cable Arcnet connectors, using 93 ohm RG-62a/u coax cable, also used 50 ohm BNC connectors. The terminators were 93 ohm resistors inside 50 ohm BNC connectors: http://theory.cs.uni-bonn.de/info5/system/arcnet.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
BNC connectors 75 Ohm versus 50 Ohm?
Roy Lewallen wrote:
I also have a lot of RG-59 cables with 50 ohm BNC connectors. That's probably more common, since 50 ohm connectors are much more common, and the connector choice won't make any practical difference in the vast majority of applications. Well, we will see in a couple of weeks what I get. I broke down and bought a set consisting of a BNC crimping tool, a wire stripper and 50 rg-59 BNC plugs from an eBay store. They did not have any rg-6 plugs, so I'm hoping that the RG6-QS I've got works. It's the heavy duty kind that looks like a heavy duty side crimp tool, except that the wire goes in the top and the plug is pushed together from the handle end (bottom). I'll report back. Thanks for all the help and support so far. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
On Mon, 7 Jun 2010 02:24:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote: Well, we will see in a couple of weeks what I get. I broke down and bought a set consisting of a BNC crimping tool, a wire stripper and 50 rg-59 BNC plugs from an eBay store. What's the item number? I'll check if you bought the correct connectors for RG-6a/u QS coax. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
BNC connectors 75 Ohm versus 50 Ohm?
Jeff Liebermann wrote:
On Mon, 7 Jun 2010 02:24:04 +0000 (UTC), "Geoffrey S. Mendelson" What's the item number? I'll check if you bought the correct connectors for RG-6a/u QS coax. Thanks. 380197598600 Though to be honest, if they are not the correct ones, I'll still probably use them anyway. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or understanding, as in he has a sub-wikipedia understanding of the situation. i.e possessing less facts or information than can be found in the Wikipedia. |
BNC connectors 75 Ohm versus 50 Ohm?
Jeff Liebermann wrote in
: I like Thomas and Betts Snap-n-Seal connectors: These are known generically as "compression connectors", and I recommended the BNC type earlier, because when used with either a BNC-F on the antenna, or a BNC/N adapter to an N-F they are waterproof, and neither depends critically on the retaining nut torque for good electrical connection (as do UHF, SMA and F connectors). Compression connectors do not use a normal hex crimp tool, but a tool unique to themselves, and in the rest of the world, the tools are pretty inexpensive (US20). Whilst I say they are waterproof, with force, it is possible to break the front of the connector out of the connector body in the types that I have tested. If you use ordinary (ie non waterproof) crimp BNCs, you need to figure some way to waterproof the cable jacket to the connector body. Most do not lend themselves to glue lined heatshrink for this purpose. Of course, you could always treat them like UHF series, and wrap the entire joint. Owen |
BNC connectors 75 Ohm versus 50 Ohm?
On Jun 7, 7:54*am, Owen Duffy wrote:
Jeff Liebermann wrote : I like Thomas and Betts Snap-n-Seal connectors: These are known generically as "compression connectors", and I recommended the BNC type earlier, because when used with either a BNC-F on the antenna, or a BNC/N adapter to an N-F they are waterproof, and neither depends critically on the retaining nut torque for good electrical connection (as do UHF, SMA and F connectors). Compression connectors do not use a normal hex crimp tool, but a tool unique to themselves, and in the rest of the world, the tools are pretty inexpensive (US20). Whilst I say they are waterproof, with force, it is possible to break the front of the connector out of the connector body in the types that I have tested. If you use ordinary (ie non waterproof) crimp BNCs, you need to figure some way to waterproof the cable jacket to the connector body. Most do not lend themselves to glue lined heatshrink for this purpose. Of course, you could always treat them like UHF series, and wrap the entire joint. Owen BNC's are still 50 or 75 Ohm. Old versions had different diameter centre pins in order to acheive the correct characteristic impedance. If you plugged a 50 Ohm plug into a 75 Ohm socket the larger centre pin would splay out the female centre connector, so when you plugged a 75 Ohm back in again it wouldn't make contact. It used to be fairly common practice to paint the body of the connector purple or green in order to quickly identify the type and so prevent damage. For the past 20 or so years most manufacturers have used the same sized centre pin, but the 50 Ohm version has a PTFE skirt in order to provide the correct charateristic impedance. So they are now mechanically interchangeable. UKM |
BNC connectors 75 Ohm versus 50 Ohm?
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BNC connectors 75 Ohm versus 50 Ohm?
On Jun 7, 2:11*pm, Gaius wrote:
In article fda40c34-830f-438d-830e-0c1c23d2bc44 @c10g2000yqi.googlegroups.com, says... BNC's are still 50 or 75 Ohm. Old versions had different diameter centre pins in order to acheive the correct characteristic impedance. Can you (or anyone !) provide some evidence of this, in terms of actual measurements or manufacturers' specifications showing a difference in the "Old" versions ? You are also confusing the effects of conductor diameter versus mating surface diameter. 75R and 50R STILL have different inner conductor diameters to achieve correct Zo; it's the MATING SURFACES which are the same. If you plugged a 50 Ohm plug into a 75 Ohm socket the larger centre pin would splay out the female centre connector, so when you plugged a 75 Ohm back in again it wouldn't make contact. It used to be fairly common practice to paint the body of the connector purple or green in order to quickly identify the type and so prevent damage. I (professionally) used many thousands of BNCs during the timescale you mention. While it IS true that some 75R sockets could be damaged, in EVERY case it was due to the inner conductor of the plug being off- centre. 75R sockets were/are inherently rather fragile. The problem was caused by a mechanical design weakness in some brands of plugs (I don't remember which manufacturers). AFAIR, the BBC used 50R plugs/sockets in some 75R video equipment, simply because the 50R socket was more robust, by design. For the past 20 or so years most manufacturers have used the same sized centre pin, but the 50 Ohm version has a PTFE skirt in order to provide the correct charateristic impedance. So they are now mechanically interchangeable. I have lots of old stock and recovered BNCs dating back at least 20 years. All the 50R and 75R components mate without problem. Well I've got some old 75 Ohm female to female adaptors in front of me, marked RS part number 455-933 (but the type associated with the part number has changed many times over the years). I also have one marked G37534 which looks fairly similar. Most have been opened up because they have had a 50 Ohm shoved into them. However on the one pristine 75 Ohm adaptor I could find, the outer part of the 75 Ohm centre receptacle is so narrow it would easily fit the inside of a 50 Ohm centre receptacle. Unfortunately I can’t find any old Greenpar (or similar) mechanical drawings on the web only the newer types. UKM |
BNC connectors 75 Ohm versus 50 Ohm?
On Jun 7, 3:02*pm, UKMonitor wrote:
On Jun 7, 2:11*pm, Gaius wrote: In article fda40c34-830f-438d-830e-0c1c23d2bc44 @c10g2000yqi.googlegroups.com, says... BNC's are still 50 or 75 Ohm. Old versions had different diameter centre pins in order to acheive the correct characteristic impedance. Can you (or anyone !) provide some evidence of this, in terms of actual measurements or manufacturers' specifications showing a difference in the "Old" versions ? You are also confusing the effects of conductor diameter versus mating surface diameter. 75R and 50R STILL have different inner conductor diameters to achieve correct Zo; it's the MATING SURFACES which are the same. If you plugged a 50 Ohm plug into a 75 Ohm socket the larger centre pin would splay out the female centre connector, so when you plugged a 75 Ohm back in again it wouldn't make contact. It used to be fairly common practice to paint the body of the connector purple or green in order to quickly identify the type and so prevent damage. I (professionally) used many thousands of BNCs during the timescale you mention. While it IS true that some 75R sockets could be damaged, in EVERY case it was due to the inner conductor of the plug being off- centre. 75R sockets were/are inherently rather fragile. The problem was caused by a mechanical design weakness in some brands of plugs (I don't remember which manufacturers). AFAIR, the BBC used 50R plugs/sockets in some 75R video equipment, simply because the 50R socket was more robust, by design. For the past 20 or so years most manufacturers have used the same sized centre pin, but the 50 Ohm version has a PTFE skirt in order to provide the correct charateristic impedance. So they are now mechanically interchangeable. I have lots of old stock and recovered BNCs dating back at least 20 years. All the 50R and 75R components mate without problem. Well I've got some old 75 Ohm female to female adaptors in front of me, marked RS part number 455-933 (but the type associated with the part number has changed many times over the years). I also have one marked G37534 which looks fairly similar. Most have been opened up because they have had a 50 Ohm shoved into them. However on the one pristine 75 Ohm adaptor I could find, the outer part of the 75 Ohm centre receptacle is so narrow it would easily fit the inside of a 50 Ohm centre receptacle. Unfortunately I can’t find any old Greenpar (or similar) mechanical drawings on the web only the newer types. UKM- Hide quoted text - - Show quoted text - Looks like they were prior to IEC 169-8 (1978) which defined mechanical interchangeability. UKM |
BNC connectors 75 Ohm versus 50 Ohm?
On Mon, 7 Jun 2010 14:11:58 +0100, Gaius wrote:
In article fda40c34-830f-438d-830e-0c1c23d2bc44 , says... BNC's are still 50 or 75 Ohm. Old versions had different diameter centre pins in order to acheive the correct characteristic impedance. Can you (or anyone !) provide some evidence of this, in terms of actual measurements or manufacturers' specifications showing a difference in the "Old" versions ? I downloaded the mechanical drawings from the Amphenol web pile and found that the center pin diameter is missing from the drawings. I'll look elsewhere when I have time. http://www.amphenolconnex.com/products/bnc.asp I have a box full of 75 coax patch cables I salvaged from a radio station cleanup. They all mate fine with a 50 ohm BNC jack. The only difference is that the 75 ohm plug has no dielectric, while the 50 ohm jack does. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
BNC connectors 75 Ohm versus 50 Ohm?
Jeff Liebermann wrote:
On Mon, 7 Jun 2010 14:11:58 +0100, Gaius wrote: In article fda40c34-830f-438d-830e-0c1c23d2bc44 @c10g2000yqi.googlegroups.com, says... BNC's are still 50 or 75 Ohm. Old versions had different diameter centre pins in order to acheive the correct characteristic impedance. Can you (or anyone !) provide some evidence of this, in terms of actual measurements or manufacturers' specifications showing a difference in the "Old" versions ? I downloaded the mechanical drawings from the Amphenol web pile and found that the center pin diameter is missing from the drawings. I'll look elsewhere when I have time. http://www.amphenolconnex.com/products/bnc.asp I have a box full of 75 coax patch cables I salvaged from a radio station cleanup. They all mate fine with a 50 ohm BNC jack. The only difference is that the 75 ohm plug has no dielectric, while the 50 ohm jack does. http://www.wbdg.org/ccb/FEDMIL/prf39012_16h.pdf is the MIL drawing for the plug. note they only have ONE drawing for the center contact. They also call out MIL-STD-348 for the pin contact interface. http://www.dscc.dla.mil/Programs/Mil...oc=MIL-STD-348 http://www.dscc.dla.mil/Downloads/Mi...8/idstd348.pdf is probably the one you want. on the plug/pin, dimension C (the ID of the insulation inside the outer conductor) has a minimum, but no maximum. Likewise on the socket, dimension E, which mates with dimension C on the plug does have a maximum, but no minimum, implying you can have a "no dielectric" version. Dimension D on the plug (the pin diameter) has only one value 0.052 to 0.054 inches. Dim M on the socket (OD of center conductor) is 0.081 to 0.089, presumably to correspond roughly with dimension R on the plug, which is the same. |
BNC connectors 75 Ohm versus 50 Ohm?
In message , Owen Duffy
writes "Geoffrey S. Mendelson" wrote in : 1. Can I connect a 75ohm BNC plug (which is a different size) to a 50oHm BNC socket? There is such a thing as a 75 ohm BNC connector, but you are almost certainly looking at 50 ohm connectors designed for use on 75 ohm cable. My recollection is that the 75 ohm connectors are incompatible with the 50 ohm connectors, and in some combinations will spread the female inner part. For all intents and purposes, 50 and 75 ohm BNCs (both male and female) are interchangeable. They have essentially the same dimensions. You might just see that the 50 ohm male has a rather stubby point, whereas the 75 ohm version has a somewhat more steadily-tapered pin - but, unlike N-connectors, the 50 ohm male certainly doesn't cause damage to a 75 ohm female. The thing which mainly causes the impedances to differ is the amount of PTFE dielectric present, in both sexes. On the 75 ohm version, you will normally see that it has been reduced considerably compared with the 50 ohm. Even with less dielectric, the 75 ohm version is still a bit unhappy with having too much, and this tends to lower the impedance to somewhat less than 75 ohms. However, for all intents and purposes, you probably won't notice any significant difference between 50 and 75 ohm BNCs (mixed or not). -- Ian |
BNC connectors 75 Ohm versus 50 Ohm?
Time to sum up where we are in this cause célèbre, I think.
The diameter of the centre pin in current production BNC plugs is specified as between 1.32 and 1.37mm (0.052 and 0.054 inches). This is the same for 75R connectors which are detailed in MIL-STD-348B (9Feb 2009), and 50R connectors, shown in MIL-STD-348 (20 April 1988). The earlier document does not refer to the Zo, but the drawing is clearly of a 50R socket with the extended dielectric surrounding the split pin. Therefore - all compliant BNC connectors are mechanically compatible between 50R and 75R from April 1988 onwards. There are NO mating damage problems for current production items. It has been suggested that prior to the introduction of IEC 169-8 in 1978, which defined interchangeability, there may have been differences in the pin diameters between 50R and 75R plugs. This will only be resolved by the actual measurement of plugs known to have been manufactured prior to 1978 - or someone producing specification documents from the time. The definitive specification of BNC connectors would appear to be contained within IEC standard document 169-8. This does not seem to be easily available - copies must be purchased at considerable expense from the IEC. Has anyone got access to a copy of this document ? |
BNC connectors 75 Ohm versus 50 Ohm?
N connectors don't have any dielectric in the mating region, so the pin
diameter would have to be made smaller for a 75 ohm impedance. Maybe N connector incompatibility issues have morphed into misconceptions about BNCs. I don't think I have any 75 ohm N connectors (assuming such things exist) to look at. Roy Lewallen, W7EL |
BNC connectors 75 Ohm versus 50 Ohm?
In message , Roy Lewallen
writes N connectors don't have any dielectric in the mating region, so the pin diameter would have to be made smaller for a 75 ohm impedance. Maybe N connector incompatibility issues have morphed into misconceptions about BNCs. I don't think I have any 75 ohm N connectors (assuming such things exist) to look at. That certainly explains why the diameter of the 75 ohm N pin is much, much less than the 50 ohm. The two are certainly not mateable. I must admit that, in the back of my mind, I'd occasionally wondered why - and now, after over 46 years of successfully not getting them mixed up too often (at work, it was a hanging offence to put a 50 ohm male in a 75 ohm female), all is clear! I don't know why it never dawned on me. I'm fully familiar with the difference between the BNCs. -- Ian |
BNC connectors 75 Ohm versus 50 Ohm?
On Sun, 06 Jun 2010 19:19:42 -0400, John Passaneau
wrote: *Snip* No the size of the center conductor pin is different between 75 and 50 ohm connectors and will either make bad contact or damage the socket. *Snip* John Passaneau W3JXP Not in years, they used to be made with different sized pins but now rely on different dielectrics for impedance. H. Who used to get yelled at by his boss for inserting 50 ohm males into 75 ohm females. |
BNC connectors 75 Ohm versus 50 Ohm?
[Sorry for being a little late to the party, but I was off newsgroups most of this week.] This thread had some discussion of adapters and I want to share my bad experience with some low-cost items, proving, once again, that you get what you pay for. I am testing all my adapters and discarding some because the assemblies are pulling apart with very little force. One manifestation: tightening the threaded ring on a PL-259 (either cable end connector or adapter) and having the ring just continue all the way on, separating from the connector body. One test for a future failure has been any lack of smoothness when I rotate the ring while tugging it gently. If it binds, rather than turning smoothly in my hands, it's going to fail. Also, some of the cheap connectors are press-fit together very poorly; they pull apart with only a few pounds of pull. Most of my early exposure to coax connectors was in and around the US Navy, where reliable connectors are the rule, so I was a spoiled child. "Sal" (KD6VKW) |
BNC connectors 75 Ohm versus 50 Ohm?
On 06/13/2010 01:50 PM, Sal M. O'Nella wrote:
[Sorry for being a little late to the party, but I was off newsgroups most of this week.] This thread had some discussion of adapters and I want to share my bad experience with some low-cost items, proving, once again, that you get what you pay for. I am testing all my adapters and discarding some because the assemblies are pulling apart with very little force. One manifestation: tightening the threaded ring on a PL-259 (either cable end connector or adapter) and having the ring just continue all the way on, separating from the connector body. One test for a future failure has been any lack of smoothness when I rotate the ring while tugging it gently. If it binds, rather than turning smoothly in my hands, it's going to fail. Also, some of the cheap connectors are press-fit together very poorly; they pull apart with only a few pounds of pull. Most of my early exposure to coax connectors was in and around the US Navy, where reliable connectors are the rule, so I was a spoiled child. "Sal" (KD6VKW) PL-259's I can handle. BNC's drive me nuts trying to get a good connection. I gave up and just buy my cables now. Bill |
BNC connectors 75 Ohm versus 50 Ohm?
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BNC connectors 75 Ohm versus 50 Ohm?
Sal M. O'Nella wrote:
After I got out of the Navy, I worked as a Marine Electrician, installing equipment on Navy ships. My foreman told me that it is rarely done, but the Navy can perform a Quality Assurance "pull test" of 25 lbs on a connector. I think that's a lot of pull for a connector to withstand. In a previous life I was tasked with tailoring a large number of RG-58 cables connecting radar scopes at a new installation in Korea. This involved cutting the cables to length and installing clamp and solder type BNC connectors. The rumor was that the Korean troops were supposed to be helping us, but we never saw them -- until one day, when they showed up. The one assigned to help me sat down and, neither of us being fluent in the other's language, I proceeded to show him how to assemble the connector. Now the job of one of the several pieces, a metal ring, is to push against and expand a rubber washer, which is mainly what holds the connector together. This piece looks like it should go upside down from the correct orientation, but if put on that way, the rubber washer won't expand and the connector will come off very easily, with only a gentle tug. If assembled correctly, it'll take a lot of pulling, as Sal says, to get it off. I've never seen a correctly assembled connector come off. Getting back to the story, I carefully demonstrated the correct assembly method to the Korean troop, emphasizing the orientation of the ring. After putting the connector on, I showed him our standard test. We would grab the connector in one hand and about two feet down the cable with the other. Then we put our hands together, making a loop of cable, and briskly yanked them apart, resulting in a really good sharp tug on the connector. A properly assembled connector had no trouble with this test. So I gave him the parts and went to work on a connector. After a while he handed me the cable with attached connector. I gave it the tug test and the connector snapped right off. So I repeated the mimed instructions, with extra emphasis on the ring orientation, then put him to work again and got back to what I was doing. When he was finished he handed me the connector, I did the yank test, and again the connector popped right off. He shrugged, muttered something under his breath, got up, and left. Guess he figured he'd had enough of that game, where he assembled connectors and I pulled them off. We never saw the Korean troops again. Roy Lewallen, W7EL |
BNC connectors 75 Ohm versus 50 Ohm?
Roy Lewallen wrote in
: I've never seen a correctly assembled connector come off. Another story, but with a different outcome. I worked in a training school at one stage, and we thought we would get trainees to make up BNC RG58 patch cables as a practical exercise, and we would feed the output into our satellite labs where cables didn't seem to last long (trainees pulled equipment trolleys around by the coax if it didn't reach the desired socket). Total failure, the BNC field serviceable connectors were just too complicated for dissinterested trainees more interested in discussing fast cars than concentrating on the job... and they had no stake in it, if the cables didn't work, it didn't matter too much. Solving the problem of the connectors pulling off led me to the Amphenol specs, and I found that the pull out spec for the field serviceable connectors was *much* lower than the spec for the crimp connectors. So, I bought a quality crimp tool (in those days, it was a few hundred dollars), and some Kings crimp connectors, and we switched the classes to use the crimp components and a trim jig. The outcome was much better, fewer faulty cables, and the crimped cable retention was much better and consistently so. No I know that one of the large suppliers to hams advertises "crimped, not soldered", but that is just a blatant case of playing to the market. A bit like the single core 4:1 Guanella balun that manufacturers attribute to Sevik's assurance that it will work fine on a fully floating load... whan antenna system is a fully floating load. The theme is the customer is always right, if he wants something that doesn't make sense, see Rule 1. An interesting new connector type is the "compression connectors", "Snap- n-Seal" is a proprietary name. I tried some of these on RG6, and a bit suspicious of the cable retention mechanism, every one I tested using different types of RG6 (including QS), hung on until the cable tore apart some distance from the connector. Owen |
BNC connectors 75 Ohm versus 50 Ohm?
Owen Duffy wrote in news:Xns9D9948E3052AFnonenowhere@
61.9.191.5: No I know that one of the large suppliers to hams advertises "crimped, not soldered", but that is just a blatant case of playing to the market. Got that back the front, didn't I. DXE advertises "soldered, not crimped", but that is just a blatant case of playing to the market. Owen |
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