If the CATV industry likes them, well, I'm happy they're happy. Instrument use is quite a different regime. F connectors use the centre conductor of the coax as the contact, and are very susceptible to damage with repeated mating cycles. The ones I've seen are also fairly far from constant-impedance.
BNCs and SMAs for me.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
The CATV industry is never happy. If it were happy, innovation would cease and the status quo would become permanent.
I believe that I mumbled something about "for the intended purpose". I don't think anyone uses F-connectors for precision test equipment. They're not really good enough. Looking at the pile, most of my CATV specific test equipment uses BNC connectors. However, that's not because the F-connector is in some way electrically inferior. It's because the F-connector receptacles were not designed to survive repeated insertion/removal cycles. The few that have built in F-connectors allow for easy replacement, such as my Wavetek SAM-1000 which uses a panel mounted F barrel adapter.
The F-connector is certainly not constant impedance. On a TDR, the bump is rather obvious. Yet, some cable and connector combinations are rated and tested to 4.5GHz: The recommended connectors are T&B SNS1P6 or FSNS6U compression F-connectors.
I partly agree with you about center conductor problems. I assume that you're referring to the copper plated steel center conductor, found in most cheap RG-6/u cables, which is not intended for repeated insertion/extraction cycles. Still, the rating is 500 insertion/extraction cycles minimum. The copper will eventually scrape off. However, solid copper center conductor RG-6/u (such as Belden 1694A) works quite nicely, without any damage. I couldn't find a spec for insertion/extraction cycles for 1694A.
Crimp or compression plugs, in quantities of 100 on eBay: F-connector $0.30/ea SMA male $0.70/ea BNC male $1.00/ea For test equipment, the price difference is not enough to justify using the cheapest. For CATV, which consumes connectors by the millions, every penny counts.
Thanks.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Which end is the head? (Sorry, I couldn't resist).
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Sure, horses for courses. I'm not telling them how to run their lives, because I couldn't care less about their lives. ;) (Well, as individuals, sure, but as for the industry, if CATV went away completely tomorrow, it would suit me fine--provided only that they took their tarts and talking heads with them.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I assure you that the selection of RF connector will have no effect on CATV content quality. I like the tarts, but can do without the talking heads.
For what little it's worth, I didn't own a TV for about 15 years. Except for being somewhat culturally deprived, I didn't miss TV in the slightest. However, I then picked up a contract to review some technical videos and needed a TV and VCR to play them. I soon found myself watching broadcast TV, buying DVD's, putting together a media center, subscribing to DirecTV, Netflix, etc. Today, I find that I can't sleep without the TV running. I'm now watching a 1931 Boris Karloff movie as I type. I'm addicted.
Hint: Don't judge connectors by the content they carry.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Nah, sufficiently crappy connectors could improve the content a lot. ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
If you have to ask, you aren't qualified for the job. :)
The entire system of amplifiers is marked as Forward or Reverse so just follow the reverse path to the head end. Unless it's Fiber enhanced CATV.
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
It's easier to find in the dark if you feel for it. I knew a lot of CATV people, including the Chief Head End Technician at Time Warner in Houston; and we prized the supple stuff for personal use.
I had a full 1000' spool stolen from me.
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
That just sounds like another excuse to the use the butane torch :)
Steel, ment to be clamped not soldered?
-- John G Sydney.
Most of the rg-6 uses aluminum instead of copper or tinned copper. The normal methods of soldering will not work on it.
You're doing it wrong: never wait for dry metal to melt solder opposite the iron. Tin under the iron, so there's thermal transfer. Then go around the braid, spreading the tinned area around it. Mind the core will melt to goo while you're doing this...
And as others have mentioned, if it's aluminum or stainless, you're screwed.
Tim
-- Seven Transistor Labs, LLC Electrical Eng>
I'll believe Aluminium or steel I must admit to only a little actual experience. Some Cable guy should give an actual answer.
-- John G Sydney.
The original RG6 used a copper center conductor, and a copper braid over a stiff, solid insulator. It was barely useful for video. The RG6/U used for CATV has a copper plated steel center conductor, foam inner insulator and aluminum foil covered by aluminum drain wires. If it is to be used overhead, it has a separate stainless steel 'messenger' wire with a Siamese outer jacket over both the coax and the messenger strand. I worked in CATV, and used to see 50,000 feet of it come in at a time. The best way to be sure is see who made the cable in question, and look up the OEM's specifications for that exact type of cable.
We used Belden, Commscope, and other American made brands back in the mid '80s.
He got most of it right.
As a former installer of a dual system (Cube) (Time/Warner)(Warner/ Amex)We had dual 'siamesed' cables and those used for "drops" had the messenger strand.
However, ALL of it, indoor, outdoor, drop lines, and UG (underground) ALL had a braided tin plated copper braid over the foil layers. The foam core had a laminated immobile foil affixed to it, and then there was foil and braid over that. I know because foil tears and braid does not, and the fittings used in the industry get crimped on, and foil alone will not endure those stresses over time, if not fail immediately.
But RG-6 can be bought in many different configurations. It is more about the form factor and physical size and characteristic impedance. RG-59 was the same impedance but slightly smaller but had a higher capacitance per foot and could not be used on longer runs, whereas the RG-6 could perform over greater distances Mainly due to a thicker core to shield spacing making for a lower parasitic capacitance per foot.
And you got most of that right. The RG number is mostly the physical size of the cable. The reason rg-6 size is used is for lower losses at higher frequencies. It is less expensive and able to be bent and handled in a house easier than the rg-11 size.
The main loss in the cable up; to about 1000 MHz is the resistance loss of the conductors. By making the center conductor larger there is less loss. The foil is used to provide a very good shield to keep the RF inside the cable, and the braid is mainly to provide a way to crimp it for a good electrical connection.
Nobody ever used RG-11 in a house. It was always RG-59 and now with the channel count and digital internet being added, most in-house installs are RG-6 throughout, unless it is a cheap ass cable company.
It is not mere wire resistance either. The capacitance is also a factor in why RG-6 is better than RG-59.
Another reason why mere foil shielding does not ring true. This is why the center conductor is not a copper plated steel core, but a copper CLAD steel core.
There are different braid fill levels available. It comes down to what the cable company wants to spend on their build.
The capacitance has almost nothing if anything at all to do with the losses at the cable frequencies.
If you look at the charts the capacitance is nearly the same and often the rg-59 is less than the rg-6.. The main losses is the I squared R loss of the conductors.
The stuff I use has both copper center conductor and braid. Most RG-6 uses a steel center conductor with a copper plating since the skin effect limits current flow to the surface at high frequencies and the steel provides more strength for pulling and aerial runs.
-- Rick
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