Administrative, Technology and Society

What Am I Doing Wrong?

23 Comments

I bought an HD-DVR receiver for Christmas. Which means additional cable runs, because it needs two satellite signals to record while playing real time. I’ve always used the twist-on F connectors for RG-6, but the last time the DirecTV guy came he recommended crimp-on compression connectors, for a better water seal (we always have LOS in heavy rain, which is a problem in south Florida).

So I spent the money on a DataShark crimper and a package of ten connectors. I followed the instructions, stripping the right lengths of both center conductor and plastic inner insulator (even though it looks to me like if you only do a quarter inch of bare wire, it won’t stick out enough to make contact). I’ve now wasted four of the things. None of them stay on the cable after crimping. They don’t even try. I take it out of the crimper, and it almost falls off. And of course, you can’t uncrimp to try again, so it’s a waste of almost a buck with each one. I have no clue what the problem is. I’m using standard RG-6. I can’t quite figure out what they’re supposed to be crimping to, even after looking at a crimped and uncrimped one. Anyone out there have any experience?

23 thoughts on “What Am I Doing Wrong?”

  2. I’m not familiar with that particular brand you bought, but it would be far from the first time I’ve seen connector instructions that just weren’t right. Try eyeballing the dimensions on one, it should be pretty obvious what it should measure with a good visual inspection.

    The standard type F connectors used with regular RG-6 cable are junk, anyway, as is the cable. For a bullet-proof installation use Time Microwave LMR-400 cable with the water resistant option ( basically a layer of goo _). and use 75 ohm Type N connectors with a soldered center conductor and crimped shield.

  3. If I am visualizing the problem correctly, the connector crimps onto the the insulated part that should make it possible for the center conductor to stick out with of .25″ exposed.

    Depending on the connector you may need to fold back some of the ground conductor (which as I recall looks like foil) so that when you crimp the outer part of the connector is touching the ground. The connector may also have sharp nubs that are meant to penetrate the outer insulation to make contact with the ground.

  4. Rand,

    The issue you are having is that not all cables are created equal. Even if it says RG-6, it might be a fraction of an inch smaller than what the connector manufacturer is expecting. After having run cable, network, phone and all sorts of other wiring, I’d recommend that you go back to using your twist on connectors and then waterproof the connection. There are good waterproofing gels out there. These you poor over the cable and then seal with tubing or tape. If you don’t ever care about getting to the connector again (unless in an emergency) you can coat the outside with a waterproof silicone, allow it to dry then tape it over with a good quality electrical tape. Cheap and messy but it does work.

  6. Odd… I haven’t crimped my own coax in years, but I used to help put up the big C-band dishes when I was younger, and I don’t remember ever having a RG-6 fall off.

    We used a different model crimper (that looked more like a pair of pliers–in fact, there were times when we just used lineman’s pliers to crimp a connector), but the concept was the same. First you crimp with the wide hole, and then you crimp with the small hole, and you get pretty mean with it in order to make sure it stays. When I was little, at least, correctly applying a crimp was fairly difficult because of the pressure required.

    Beyond that, it was mostly something you got used to and knew the force required by heart. My own guess is that you’re not being mean enough with it or not using the smaller hole to finish it off. Don’t worry too much about overcrimping, it’s less likely to happen than undercrimping, and the consequences are not really any worse.

  7. If I could crimp with a pair of pliers, it might work. But this design is not an axial (or radial) crimp. It is a longitudinal crimp (it shortens the connector). And it doesn’t fricken’ work. At all. Ever.

    The only common element is the cabling, which is a few years old, and perhaps (as suggested in comments above) isn’t as wide as expected.

    So much for standards…

  8. Wait… RG-6 connectors that you squash vertically? I’ve never even heard of such a thing. Is it supposed to compress inwards as it compresses lengthwards?

  9. After googling…

    Is this something like what you have?

    http://www.arrisistore.com/digicon/Digicon-F-Connector-Installation-Guide.pdf

    Interesting… I didn’t know they had anything like that. I wish I could be of more help, but other than noting that the link above uses a totally different type of crimper, I don’t have a good guess as to what’s going wrong.

    FWIW, we used something more like:

    http://www.lanshack.com/Quick-Cat-RG-6-Quad-Shield-Hex-Crimp-Connector-Singles-P2634C0.aspx

    And here’s a video showing how you do both kinds (http://www.lanshack.com/HowtoVideo-RG6-Quadshield.html). I think he overdoes the part about pushing back the braiding, but otherwise it’s good. For outdoor use–such as where the coax comes out of the ground and goes up to the feedhorn on a C-band dish (leaving the RG-6 often exposed to the elements on a C-band feedhorn)–we just used a RG-6 hex connector and a few rounds of the ubiquitous black electrician’s tape. Never really had problems with water getting past that, over hundreds of installations.

  10. I’m going to be a *really* big help here, Rand, as I know exactly what you’re talking about, but I’m drawing a blank on brand-names and distributors that would be of help to you.

    All I can tell you right now (until I go back to work on Monday) is that I do some work for an outfit that does all manner of low-voltage electrical/electronic work, and we use the sort of fittings you’re talking about for all our RF cable work. Ninety-nine percent of the time they work flawlessly, and when they don’t it’s usually because the cable is not the right size for some reason. (Oftentimes we have to use what cable is already in place, and if it’s plenum-rated, it’s a bear to work with.)

    Make sure the cable isn’t riser- or plenum-rated. Look for markings such as “CMR”, “CMP”, “CL2R”, or “CL2P”. You want just plain “CM” or “CL2″ cable. (Unless your local electrical code states otherwise, of course.)

    We use stripping and flaring tools that make the job a snap. (Again, if I could only remember the makers of our tools and connectors, I could send you in the right direction. Grrrr….)

    For now (assuming your connectors are similar to what we use at CES) strip off 3/4″ of the outer jacket and the braid. Don’t worry about the foil– most of it is going away in the next step, so if you nick it, it doesn’t matter.

    Then strip off enough of the foam dielectric (the inner insulation) to leave about 3/8″ or 7/16″ of the center conductor showing. That should leave you with about 1/4″ – 5/16″ of the foil-wrapped foam dielectric still sticking out from the outer jacket.

    (Yes, the dimensions are a bit loosey-goosey, but they’re also not that critical, unlike what you have to go through in trying to solder a BNC onto RG-58. Yuck.)

    Take your flaring tool (if they provided you with one– they should have) and flare the outer jacket out– the flaring tool should slide over the inner dielectric and then under the outer jacket to a depth of maybe a quarter-inch or a little more.

    At this point, the coax should be ready to accept the connector. The connector should slide right on the coax, with the outer jacket disappearing into the back of the connector to the extent of maybe 5/16” or so. (If the center conductor juts way too far out the front of the connector, don’t worry about it– you can always trim it back.) The key thing is to make sure that the foam dielectric comes all the way up the “throat” of the connector and is even with the bottom of the “bowl” (where the connector body widens out and becomes threaded).

    Place the assembled coax and connector in your compression tool and telescope the connector.

    You *should* have a properly terminated cable.

    Check that the connector is firmly attached to the cable. (I hope so for the sake of your sanity!)

    Check that the foam dielectric is still even with the bottom of the bowl. (Out 1/16″ and in 1/8″ is OK.)

    Trim the center conductor so that it sticks out beyond the connector maybe 1/8″, and you’re done.

    I hope this is helpful…..

  11. I don’t have any advice, I just love how a guy who builds rockets is having a problem crimping a connector.

  14. Ninety-nine percent of the time they work flawlessly, and when they don’t it’s usually because the cable is not the right size for some reason.

    That’s all that I can think, is that the cable is thinner than the connector was designed for, despite the fact that it’s RG-6. And I was using cable on hand, and trying to avoid buying new.

  16. There are definitely different diameter cables out there, and I’d suspect that, too. Further than that, I’ve no idea. I use RG-8, RG-8X, RG-58 and 59 for amateur radio applications, but I always solder BNC or PL-259s on the end. Never used the crimp-on style.

  18. I hate those frickin’ things. Hex crimp, followed by 3M heatshrink, the kind with hot glue inside to seal, is the way to go.

    The problem is that in the cable and connector business, “standard” is just a short way of saying “trap ’em into buying everything out of our proprietary line.” This is a particularly egregious example. Note that DataShark is a Paladin Tool trademark, but isn’t even mentioned on their Web site!

    It’s very likely that what you have is single-shield cable and connectors designed for double shielded. You can’t tell the difference without looking up the model numbers. If so, you can make them work.

    After stripping the cable, but before flaring the braid back over the jacket, wrap a single layer of tape around the jacket right at the end. Then push the braid back over it and crimp.

    The other way to do it is to use a short piece of the smallest shrink that will go over the cable, instead of the tape. You don’t want a piece of big shrink, because when it shrinks down it’ll be too thick.

    Either way, you want to make the cable jacket large enough that the crimp engages it. In cases where water sealing isn’t important, I’ve used aluminum foil and even paper. Don’t worry about SWR. You did leave the foil in place around the center insulation, right? That’s what maintains the impedance.

    Regards,
    Ric

  20. Oh! hey I found this super ninjafied crimper for rg-6 connecters.

    It’s this complex tool that I like to call, A set of pliers.

    I know!

    It’s like. . . WOW!

  22. I had the same problem this weekend. Problem i had was that i was using compression connectors that were for both RG6 and RG6 Quad. They kept slipping out no matter what. I ended up buying to RG6 only connectors at Lowes made by IDEAL. And for a tight fit i made sure that when i stripped the cable with the stripper that i tried to leave the braid so that i could fold it back. Some strippers will cull at the way thru the braid since the cable might be a tad bit thinner than some cables. Once i did that everything held on tight. Hope this helps someone.

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