The most important about Canare RCA is that the only one claims to have an impedance at 75 ohms.
Anybody use these for 1694a with RCA ends?
In searching for a cheaper solution to the Canare ends and tools, I found a company, Gem Electronics, that sells snap and seal stuff. The tool is only about $60, and the gold RCA ends are $2.40/ea. The tool also does F and BNC.
Site is http://www.gemelec.com/snap+seal.htm .
http://www.gemelec.com/compseal7.jpg
http://www.gemelec.com/compseal10.jpg
Site is http://www.gemelec.com/snap+seal.htm .
http://www.gemelec.com/compseal7.jpg
http://www.gemelec.com/compseal10.jpg
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I just got off the phone with the manufacturer and they say they are 75 ohms. He says they are selling these like hot cakes in FL with all the HTs going in there.
He says they dont have any spec sheets or anything to prove it though. Does anyone know how to verify if they are indeed 75ohm? I dont think you can just put a meter on it, cause it is impedence, not resistance. Or maybe it is that simple??
He says they dont have any spec sheets or anything to prove it though. Does anyone know how to verify if they are indeed 75ohm? I dont think you can just put a meter on it, cause it is impedence, not resistance. Or maybe it is that simple??
Impedance is a complex subject. A reputable connector manufacture should be able to supply a "Smith Chart" for the connector. Using this you can determine the impedance characteristics.
That said what does it matter for an HT cable? Even if you are getting 30mhz at 1db, which by the way you are not with consumer HT gear, What is the half wavelegnth of 30mhz? A lot longer than a 1inch long connector. Translation: the impedance of a single or even two connectors won't have any effect on your picture quality. When many analog connectors are passed through or when using digital video signals at 270mbs and higher does the connector impedance become critical.
For many years all BNC connectors were 50ohms. In broadcast television at NTSC frequencies it made no difference even with tens of connectors in series. Digital video foced the adoption of true 75ohm connectors.
That said what does it matter for an HT cable? Even if you are getting 30mhz at 1db, which by the way you are not with consumer HT gear, What is the half wavelegnth of 30mhz? A lot longer than a 1inch long connector. Translation: the impedance of a single or even two connectors won't have any effect on your picture quality. When many analog connectors are passed through or when using digital video signals at 270mbs and higher does the connector impedance become critical.
For many years all BNC connectors were 50ohms. In broadcast television at NTSC frequencies it made no difference even with tens of connectors in series. Digital video foced the adoption of true 75ohm connectors.
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But wont an impedance mismatch ANYWHERE in your cable throw off the ENTIRE cable? My component cables will be about 52' long. This is about half a wavelength for the upper end of the video frequency spectrum (~10MHz). At that length wont it be VERY important to be as close to 75 as you can get?
| Originally posted by Glimmie Translation: the impedance of a single or even two connectors won't have any effect on your picture quality. |
Out here on the West Coast, there is a store named Platt Electronics. They sell a brand (don't know the name and the bag is at my new house) of terminators (F, BNC, RCA) that are compression type. A bag of 100 is ~$40 (ie. ~40 cents each). They are good quality construction and come in versions made for RG-59, RG-6, and RG-6QS cable.
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No, that 1 or 2in mismatch will have no effect even at 30mhz. It is cummulative so 52 inches worth of these connectors will cause a problem.
Like I said, until digital video became commen in the eraly 1990s, 75ohm BNC connectors were very rare. Reason is that BNC connectors are also used in RF systems where the commen impedance is 50ohms. As these devices are at higher frequencies, the manufactures made the connectors 50ohms to suit the RF people. NTSC video equipment was not bothered by this small mismatch. Now when we started sending digital video around at 270mbs, this small mismatch became an issue. Not so much for a few connectors but in a large television plant there can be tens on connections in series through bulkheads and patch panels. Ten 50ohm connectors at 10mhz has very small if any effect in the signal quality. At 270mbs, it can cause unrecoverable signals. Digital HDTV is at 1.5gbs or 745mhz. Here true 75ohm connectors are even more critical.
Remember too that even if you have a true 75ohm RCA connector what is the mating connector in the equipment? What is the cable or PCB trace impedance to te first active circuit stage?
75ohm RCA connectors are an oximoron. If you are that concerened about impedance mismatch then don't use RCA connectors! RCA connectors were introduced in the 1940 to connect the RCA 45rpm record changers to table radios. They were OK for 6hr VHS machines because the format did far more damage to the signal than any conection could even think of. But why RCA connectors continue to be used for DVD component video or worse yet analog HDTV is just plain silly.
| Originally posted by Easley But wont an impedance mismatch ANYWHERE in your cable throw off the ENTIRE cable? My component cables will be about 52' long. This is about half a wavelength for the upper end of the video frequency spectrum (~10MHz). At that length wont it be VERY important to be as close to 75 as you can get? |
Like I said, until digital video became commen in the eraly 1990s, 75ohm BNC connectors were very rare. Reason is that BNC connectors are also used in RF systems where the commen impedance is 50ohms. As these devices are at higher frequencies, the manufactures made the connectors 50ohms to suit the RF people. NTSC video equipment was not bothered by this small mismatch. Now when we started sending digital video around at 270mbs, this small mismatch became an issue. Not so much for a few connectors but in a large television plant there can be tens on connections in series through bulkheads and patch panels. Ten 50ohm connectors at 10mhz has very small if any effect in the signal quality. At 270mbs, it can cause unrecoverable signals. Digital HDTV is at 1.5gbs or 745mhz. Here true 75ohm connectors are even more critical.
Remember too that even if you have a true 75ohm RCA connector what is the mating connector in the equipment? What is the cable or PCB trace impedance to te first active circuit stage?
75ohm RCA connectors are an oximoron. If you are that concerened about impedance mismatch then don't use RCA connectors! RCA connectors were introduced in the 1940 to connect the RCA 45rpm record changers to table radios. They were OK for 6hr VHS machines because the format did far more damage to the signal than any conection could even think of. But why RCA connectors continue to be used for DVD component video or worse yet analog HDTV is just plain silly.
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After reading up on cables and impedance the last couple of days, I agree. From what I have read, RCA's design is not condusive to making a true 75ohm connector. Apparantly BNC is a more native design for maintaining the desired impedance. I am supprised more of the high end DVD players dont offer a BNC option.
So are you saying I wont see a difference between say Radio Shack RCA connectors, and better ones like the Canare?
| Originally posted by Glimmie But why RCA connectors continue to be used for DVD component video or worse yet analog HDTV is just plain silly. |
So are you saying I wont see a difference between say Radio Shack RCA connectors, and better ones like the Canare?
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