Crimp versus twist-on BNC connectors

[stevefpi 0]

Hopefully this is an easy question. I've got a DVR setup with 8 cameras that we setup and teardown frequently. I'm about to purchase bulk RG59 siamese cable (video+power) to make our own robust cabling since the white Q-see cables are crap.

 

My questions is, crimp BNC connectors or twist on? Which is more robust in terms of durability? We usually setup and then tear down the setup within 12 hours and we're very careful with the cables but they still need to be able to stand up to the abuse.

 

Thanks!

[Soundy 1]

Twist-ons are fine... IF you do them properly. If not, they'll fall off at the slightest provocation. Regular crimp-ons are fine, but a hassle if you lose the center pin during assembly.

 

Personally, I prefer compression type.

[stevefpi 0]

Cool, I'll look into those as well! Cheers

[andyh747 0]

Sorry to hijack the thread but I have a related issue with crimp BNC connectors. I've experimented with crimping these but always have difficulty achieving a good result especially around the outer sheath. If I wiggle the coax when complete, the coax outer insulation sheath often comes out from under the crimp collar (I've been using three part connectors).

 

Any tips on getting a good crimp on RG59?

 

Alternatively anyone got any recommended suppliers for compression connectors as these appear more robust.

[stevefpi 0]

I'm currently looking at these as a possibility.

 

http://deepsurplus.com/BNC-RG59-Compression-Connectors-Nickel-Plated-Bag-of-5

[Soundy 1]

Andy, sounds like you're stripping the sheath too far back, or using the wrong connectors. If you're using FT6 (plenum) cable, the sheath is a lot thinner than with FT4 (riser), and standard connectors won't get a tight fit. Make sure you're using the proper connectors for RG6 or RG59, too, since the two cables are different thicknesses as well.

 

One thing you can do is to strip the sheath a little short, so the center barrel of the connector causes it to bulge out a bit... slip the collar into place first, then shove the barrel in, and it should make a good, tight fit even before crimping.

 

Steve, those look alright, although they seem a little overpriced to me. I use GEM's connectors, mainly (both crimp and compression), they're solid and work great with my SealTite universal compression tool: http://gemelec.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=116&category_id=22&manufacturer_id=0&option=com_virtuemart&Itemid=1

 

Trying to think of the other connectors I've used... can't think of the brand. They're really nice, including a plastic guide for the center conductor/pin... come in a funky (and frustrating) tube pack of 25. Same manufacturer makes a really slick "starter kit" with an assortment of "stubby" connectors (F, BNC, RCA, etc.), compression tool, and stripper/flaring tool. Would love to get the kit, but can't really justify it since 99.99% of my connector use are BNC and all the others would be wastage.

[Soundy 1]

Ah, here it is - ICM Corp. Check out the "DB System Starter Kit" here: http://www.icmcorp.net/ICM_featuredproducts.htm

[andyh747 0]

Andy, sounds like you're stripping the sheath too far back, or using the wrong connectors. If you're using FT6 (plenum) cable, the sheath is a lot thinner than with FT4 (riser), and standard connectors won't get a tight fit. Make sure you're using the proper connectors for RG6 or RG59, too, since the two cables are different thicknesses as well.

 

One thing you can do is to strip the sheath a little short, so the center barrel of the connector causes it to bulge out a bit... slip the collar into place first, then shove the barrel in, and it should make a good, tight fit even before crimping.

 

Steve, those look alright, although they seem a little overpriced to me. I use GEM's connectors, mainly (both crimp and compression), they're solid and work great with my SealTite universal compression tool: http://gemelec.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=116&category_id=22&manufacturer_id=0&option=com_virtuemart&Itemid=1

 

Trying to think of the other connectors I've used... can't think of the brand. They're really nice, including a plastic guide for the center conductor/pin... come in a funky (and frustrating) tube pack of 25. Same manufacturer makes a really slick "starter kit" with an assortment of "stubby" connectors (F, BNC, RCA, etc.), compression tool, and stripper/flaring tool. Would love to get the kit, but can't really justify it since 99.99% of my connector use are BNC and all the others would be wastage.

 

Thanks I'll try stripping the sheath a bit shorter. I'm using connectors designed for RG59 and the cable is definitely RG59. One other query. Do most people strip the foil sheath off as well or leave that around the central insulator before inserting into the central barrel?

[stevefpi 0]

awesome, thanks for the info. That starter kit does look cool but like you, I'm only using BNC connectors so the rest would be waste.

 

I've never bought the BNC connectors before so what would a good price range be for a bag of ten? I'll take a good look at that site you sent me. The reason I was going with that link I posted earlier is because they have good pricing on the cable spool we need.

 

Honestly, money is a huge issue as we're a non profit. I want to save money but not get shotty hardware that will need replacing in a year. If anyone can suggest a vendor for compression and/or crimp-on BNC RG59 connectors, that would be great. Also a crimping tool as well. I don't need the ones that work with 20 different types of connectors. I only use BNC so I only need one that works for RG59 BNC connectors.

 

I'm really happy to have found this forum. Thanks for all the great info!

 

cheers

[SEANHAWG 1]

 

Thanks I'll try stripping the sheath a bit shorter. I'm using connectors designed for RG59 and the cable is definitely RG59. One other query. Do most people strip the foil sheath off as well or leave that around the central insulator before inserting into the central barrel?

 

In the future, it may be better to buy the cable without the foil sheath, all that does is cause problems for your BNC connection and is not ideal for CCTV installations. But yes, if you have the cable with the sheath, then peeling it back would be a good idea.

[Numb-nuts 1]

 

In the future, it may be better to buy the cable without the foil sheath, all that does is cause problems for your BNC connection and is not ideal for CCTV installations. But yes, if you have the cable with the sheath, then peeling it back would be a good idea.

 

I'm sitting here grinning thinking should I shouldn't I ?

No I'll leave that to your imagination chaps then you've nobody to blame but yourselves.

[Soundy 1]

I'm using connectors designed for RG59 and the cable is definitely RG59. One other query. Do most people strip the foil sheath off as well or leave that around the central insulator before inserting into the central barrel?

Most of us actually use RG59 with braided copper shield... foil shield is bad, mmmkay? I suspect that's a lot of your problem there: without the extra thickness of the braid, there's not enough thickness for the crimp to clamp down on.

 

It's even worse if the center conductor is copper-jacketed steel or aluminum... which seems to often be the case with foil-shielded coax.

[Numb-nuts 1]

Just for the sake of a few pence, I have decided now to buy BNC and other crimps from Farnell and RS Components.

I know they only sell quality brand connectors like Tyco eTC Yes they cost a bit more but if a BNC fails you need to buy anotther and go replace it too better to pay twice the price and get a better BNC crimp

 

What worried me though, when I ordered them they arrived with the words TYCO 'made in taiwan'

so I am assuming they were made to a quality specification for Tyco. They appear to be a good quality but appearances as we all know can be deceptive.

These are the Farnell Offerings

 

BNC Crimps Tyco

BNC Crimps Multicomp

BNC Line Jack crimps Tyco / Greenpar

BNC Line Jacks Tyco

[andyh747 0]

I'm using connectors designed for RG59 and the cable is definitely RG59. One other query. Do most people strip the foil sheath off as well or leave that around the central insulator before inserting into the central barrel?

Most of us actually use RG59 with braided copper shield... foil shield is bad, mmmkay? I suspect that's a lot of your problem there: without the extra thickness of the braid, there's not enough thickness for the crimp to clamp down on.

 

It's even worse if the center conductor is copper-jacketed steel or aluminum... which seems to often be the case with foil-shielded coax.

 

I'm not sure you're talking about the same cable as I am. This is RG59 plus power designed specifically for CCTV use and purchased from a professional CCTV supplier who only supplies to the trade. The cable is made up of a solid copper central conductor surrounded by a foam dielectric. The dielectric then has a foil shield over it. On top of the foil shield is the copper braid outer conductor and then finally the insulating jacket. As far as I'm aware this is the best construction method for RG59 as it has the least interference.

[SEANHAWG 1]

Yes, I know exactly what you are talking about. And the foil shielded cable is not what you want to get next time. We bought a couple of rolls of that when we first started from a CCTV supplier as well. Its a pain in the butt for installing. I would think that most installers would agree that that type of cable is not ideal for CCTV. They use that type of cable alot in satellite and cable TV installations. But since you have it already, you can still use it, but you will want to peel back the foil because if that touches the inner conductor, it will kill the video signal or cause it to be really poor, thats why its a pain the butt, plus I think it may cause other problems as well. If you buy more cable in the future, it should look something like this with no foil shielding:

[andyh747 0]

Sorry I still don't understand. Peeling back the foil shield is easy but provides additional protection so please tell me why its better without it? What possible additional problems can it cause? The shielding provides additional protection from interference. Provided the centre conductor is not compromised the shielding can only enhance the signal quality.

 

Perhaps you'd like to explain the technical aspects behind why this cable performs worse than the cable you've displayed???

[Soundy 1]

What Sean's saying is that if the foil inadvertently makes contact with the center conductor, it can cause problems, that's why he's suggesting pulling it back so the barrel of the connector goes between it and the center dielectric. It's just a precaution.

 

There was obviously some misunderstanding as well, as by far the most common foil-shielded cable we see has JUST the foil, and a single drain wire running the length of the sheath. RG6 more commonly has both braid and foil, but RG59 rarely does (in fact, I don't know that I've ever seen RG59 before that had both). There's nothing wrong with foil shielding as such... the problem is when it's the ONLY shield. A good, tight copper braid (90-95% coverage) is significantly better.

[SEANHAWG 1]

Sorry if I was wrong about the extra foil wrap causing extra problems. Honestly, I dont know the technical reasons as to why it would cause more problems. I just know that noone on here recommends it. It seems I read a post not too long ago from one of the installers on here that the foil wrap can cause "extra" problems in addition to touching the inner conductor. I am just too lazy to look it up right now. I know that is good for CATV, but is not used often in CCTV.

 

All I know is that whenever we get our used cameras in from the large retailers/government organizations/casinos, they occasionally have some siamese cable attached to their cameras, and not once have I ever seen the foil wrapped stuff cable. I figure if there was a benefit to the foil wrapped stuff, then they would use it as those large organizations tend to use the highest quality equipment.

[andyh747 0]

Well from what I've seen here in the UK it's more common to have the foil shielding than not. Speaking with both trade suppliers and installers here they all use the type of cable I'm using.

 

Of course the shield could short the central conductor if poorly installed but removing it from around the central dielectric will avoid this. The foil provides more robust protection against EM interference. The only possible issue I can see is a change in impedance of the cable with the addition of the foil as well as the copper braid.

 

Anyway apart from the crimping issue I had which was down to poor technique on my part the quality of the images seems 100%.

[Numb-nuts 1]

It is quite common to have the foil shield as well as the braid, in 75ohm cable in the UK. particularly with shotgun cable.

Don't ask me why I am sure there is an explanation but I am unaware of it. Could it be to do with our damp climate perhaps?

 

The foil shield under the braid is supposed to be either a vapor barrier or loss protection I am not really sure?.

I am guessing here, but at the terminated end, it would not make that much difference if you cut the foil back.

If you did leave it intact and push it into the connector body, there is a good chance of shorting the connection,

so why take risk? It's still in contact with the braiding.

 

If the cable has a foil and no braid, get rid of it as quick as you can, it isn't suitable for cctv.

 

Good description soundy, I completely understood your description.