Which is it, RG59 or RG6?
in [Repair]
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From: Jeff Liebermann on 7 Dec 2009 14:46 On Mon, 07 Dec 2009 13:15:19 -0500, mm <NOPSAMmm2005(a)bigfoot.com> wrote: >So is there any value in getting gold-plated F connectors (if they >have them) or gold-plated A/B switches (which I know they sell)? No. The plating is so thin, that at UHF frequencies, the skin depth is less than the plating depth. If you want good RF conductivity, get silver plated connectors. The real problem with gold is dissimilar metals. Although gold will not corrode, oxidize, or rot, it will create an electrolytic junction when wet. The result is some noise, and possibly some corrosion of the other junction metal. What that means is that gold is a fair idea if you use all gold connectors, everywhere. It's not so great an idea if you mix materials. However, that's really only for exterior installations, where water can get into the connectors and devices. For indoor use, it's not so much an issue unless you live in the tropics, on a boat, or in a swamp. >It's the A/B switch I'm particularly curious about because at one >store, that was all they had, and some antenna signals are so weak, I >figured any little thing might help. > >Or other gold plated connectors? Ok, so we're off cable TV and onto OTA (over the air) issues. The biggest improvements you do for signal strength are (in order of importance): 1. Location, location, location, location, line of sight, etc. 2. Selection, design and construction of the antenna(s). 3. A tower mounted amplifier. 4. Everything else. If you've done the first 3 items, to the best your abilities and finances, then tinkering with plating materials and A-B switches is a waste of time and money. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: mm on 7 Dec 2009 17:32 On Mon, 07 Dec 2009 11:46:16 -0800, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >On Mon, 07 Dec 2009 13:15:19 -0500, mm <NOPSAMmm2005(a)bigfoot.com> >wrote: > >>So is there any value in getting gold-plated F connectors (if they >>have them) or gold-plated A/B switches (which I know they sell)? > >No. The plating is so thin, that at UHF frequencies, the skin depth >is less than the plating depth. If you want good RF conductivity, get >silver plated connectors. The real problem with gold is dissimilar >metals. Although gold will not corrode, oxidize, or rot, it will >create an electrolytic junction when wet. The result is some noise, >and possibly some corrosion of the other junction metal. What that >means is that gold is a fair idea if you use all gold connectors, >everywhere. It's not so great an idea if you mix materials. > >However, that's really only for exterior installations, where water >can get into the connectors and devices. For indoor use, it's not so >much an issue unless you live in the tropics, on a boat, or in a >swamp. I've been told it's a swamp, but I disagreed. > >>It's the A/B switch I'm particularly curious about because at one >>store, that was all they had, and some antenna signals are so weak, I >>figured any little thing might help. >> >>Or other gold plated connectors? > >Ok, so we're off cable TV and onto OTA (over the air) issues. > >The biggest improvements you do for signal strength are (in order of >importance): >1. Location, location, location, location, line of sight, etc. >2. Selection, design and construction of the antenna(s). >3. A tower mounted amplifier. >4. Everything else. >If you've done the first 3 items, to the best your abilities and >finances, then tinkering with plating materials and A-B switches is a >waste of time and money. Good to know. Thanks.
From: Ian Jackson on 9 Dec 2009 06:54 In message <W4idnbUfmb694IHWnZ2dnUVZ_gudnZ2d(a)earthlink.com>, Michael A. Terrell <mike.terrell(a)earthlink.net> writes > > The 20 dB isolation means that the return loss is more than 20 dB. No it doesn't. It means that the isolation - the loss between two outputs (with the input terminated) - is 20dB. > >This is to prevent the local oscillator from one TV causing interference >to another TV. True - but, more generally, it is to minimise the effects of something connected to one output affecting another output. As well as protecting against local oscillators, it also protects against incorrect loading (ie if an output port is not correctly terminated in a 75 ohm load). It should not matter (too much) if an output is left open circuit, short circuited, has a length of cable connected to it but going nowhere, etc etc. > I was the engineer at a CATV system with over 10,000 >active drops. There are hundreds of myths and half truths about the >hardware used for CATV systems. > Was your statement above (about RLR) one of these? [Sorry. The Devil made me say that! ;o))] > >> >I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes >> >more sense. (Actually, it should be -7.0dB loss). > While most 3-ways are typically 3.5/7/7, there are one or two around with equal outputs, of appx 5.5dB (although, personally, I can't really see much need for them). -- Ian
From: Michael A. Terrell on 9 Dec 2009 12:59 Ian Jackson wrote: > > In message <W4idnbUfmb694IHWnZ2dnUVZ_gudnZ2d(a)earthlink.com>, Michael A. > Terrell <mike.terrell(a)earthlink.net> writes > > > > > The 20 dB isolation means that the return loss is more than 20 dB. > > No it doesn't. It means that the isolation - the loss between two > outputs (with the input terminated) - is 20dB. Sigh. How do you think you measure that isolation? > >This is to prevent the local oscillator from one TV causing interference > >to another TV. > > True - but, more generally, it is to minimise the effects of something > connected to one output affecting another output. What are you connecting that doesn't have a TV tuner? FM radios are supposed to use a single port -20 dB tap. > As well as protecting > against local oscillators, it also protects against incorrect loading > (ie if an output port is not correctly terminated in a 75 ohm load). It > should not matter (too much) if an output is left open circuit, short > circuited, has a length of cable connected to it but going nowhere, etc > etc. Unterminated ports are not allowed in properly designed systems. PERIOD. > > I was the engineer at a CATV system with over 10,000 > >active drops. There are hundreds of myths and half truths about the > >hardware used for CATV systems. > > > Was your statement above (about RLR) one of these? [Sorry. The Devil > made me say that! ;o))] > > > >> >I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes > >> >more sense. (Actually, it should be -7.0dB loss). > > > While most 3-ways are typically 3.5/7/7, there are one or two around > with equal outputs, of appx 5.5dB (although, personally, I can't really > see much need for them). You would, if the use of the 3.5/7/7 would require a second drop from the line tap on the street. -- Offworld checks no longer accepted!
From: Ian Jackson on 9 Dec 2009 16:43
In message <Q-2dnRjtm4MceILWnZ2dnUVZ_vqdnZ2d(a)earthlink.com>, Michael A. Terrell <mike.terrell(a)earthlink.net> writes > >Ian Jackson wrote: >> >> In message <W4idnbUfmb694IHWnZ2dnUVZ_gudnZ2d(a)earthlink.com>, Michael A. >> Terrell <mike.terrell(a)earthlink.net> writes >> > >> >> > The 20 dB isolation means that the return loss is more than 20 dB. >> >> No it doesn't. It means that the isolation - the loss between two >> outputs (with the input terminated) - is 20dB. > > Sigh. How do you think you measure that isolation? > Sigh as much as you like - isolation and RLR are definitely NOT the same thing, and you don't measure them in the same way. > >> >This is to prevent the local oscillator from one TV causing interference >> >to another TV. >> >> True - but, more generally, it is to minimise the effects of something >> connected to one output affecting another output. > > What are you connecting that doesn't have a TV tuner? FM radios are >supposed to use a single port -20 dB tap. > That could make the FM level uncomfortably low. It's better to separate the FM from the TV signals via a bandpass diplexer filter. This is/was common practice in Europe. Of course, in the USA, you have always had your Channel 5 (running right up to the LF end of the FM band). Also, these days, you could have digital TV signals starting immediately above the FM (and still meeting the 'no interference' regulations for Air Traffic Control radio. Do any cable systems still actually carry FM radio? > >> As well as protecting >> against local oscillators, it also protects against incorrect loading >> (ie if an output port is not correctly terminated in a 75 ohm load). It >> should not matter (too much) if an output is left open circuit, short >> circuited, has a length of cable connected to it but going nowhere, etc >> etc. > > Unterminated ports are not allowed in properly designed systems. >PERIOD. > They may be installed correctly terminated, but you can bet your bottom dollar a lot won't stay that way! > >> > I was the engineer at a CATV system with over 10,000 >> >active drops. There are hundreds of myths and half truths about the >> >hardware used for CATV systems. >> > >> Was your statement above (about RLR) one of these? [Sorry. The Devil >> made me say that! ;o))] >> > >> >> >I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes >> >> >more sense. (Actually, it should be -7.0dB loss). >> > >> While most 3-ways are typically 3.5/7/7, there are one or two around >> with equal outputs, of appx 5.5dB (although, personally, I can't really >> see much need for them). > > > You would, if the use of the 3.5/7/7 would require a second drop from >the line tap on the street. > When I said "much use", I meant "MUCH use". While a computerized CATV system planner may flag up an out-of-spec condition, in practice, there may be less than 1dB difference between a nominal 5.5 and 7dB. -- Ian |