RF outdoor connector, crimp or clamp ? - Page 1
Forum section: electronics / rf-microwave

author: BravoV
author_rank: Super Contributor
timestamp: April 27, 2018, 06:39:18 am
content: As I'm planning to install my 1st outdoor GPS antenna for my GPSDO, I stumbled upon the choice of selecting connector types for N type male with LMR400 cable.As I don't own any crimping tool for this N type, and wondering the clamp type is good enough for outdoor as it will be exposed to weather. And I'm not interested to buy the crimper as it will be used only once for this installation.I live near equatorial, as typical climate with hot & intense sun and heavy rainfall.Will clamp type good enough for this installation ? Or are there any other consideration or recommendation ?Thanks in advance.Just fyi, my GPS antenna.

author: German_EE
author_rank: Super Contributor
timestamp: April 27, 2018, 07:40:11 am
content: Crimped connections are good enough for NASA and ESA so you should be OK, but if you don't have a crimp tool then use what you have.However, as you live in a country with rather more severe climate than most of us I strongly suggest that you cover the plug after connection with a few layers of self-amalgamating tape then a top layer of UV safe electrical tape. The connection should then last a long time.

author: CJay
author_rank: Super Contributor
timestamp: April 27, 2018, 01:15:34 pm
content: Clamp type connector should be fine if assembled properly and then wrapped in proper self amalgamating tape or, something I've been reliably informed is used in very harsh environments like oil rigs and ships, cold shrink tubing which is a rubber tube that's stretched over a removable spiral plastic form, you slip the whole over the cable and connector, fit the connector to the 'joint' and then pull the spiral out so the tube 'collapses' and forms a weatherproof boot.

author: CopperCone
author_rank: Super Contributor
timestamp: April 27, 2018, 01:52:10 pm
content: You can pot the thing too with epoxy

author: BravoV
author_rank: Super Contributor
timestamp: April 28, 2018, 04:36:05 am
content: Thanks guys, clamp type it is, ordered, and self amalgamating tape too.

author: kj7e
author_rank: Frequent Contributor
timestamp: April 28, 2018, 04:58:37 am
content: A factory crimped end is hard to beat. Just need to wrap the connector and coax to seal out any weather. Here are some good products to look at;https://www.rfparts.com/coaxwrap.html

author: BravoV
author_rank: Super Contributor
timestamp: April 28, 2018, 05:41:06 am
content: Quote from: kj7e on April 28, 2018, 04:58:37 amYeah, I've seen one, factory crimped coaxial connectors, really awesome.About sealing & wrapping, as above photo of my antenna, do I need to wrap to cover all the plugged N connector from the cable, up to near those 4 screws that are securing the N female port at the antenna ?

author: kj7e
author_rank: Frequent Contributor
timestamp: April 28, 2018, 01:26:28 pm
content: If you don't have the bottom mating portion, which should have a gasket seal to the antenna mounting flange, I would put some automotive silicon RTV around the base of the N connector and mounting screws. Then wrap the coax and N connector to where it seals up to the antennas N connector.

author: BravoV
author_rank: Super Contributor
timestamp: April 28, 2018, 03:59:21 pm
content: Yeah, I don't have that bottom mating part.Thanks for the tips, will do seal off those N base at the antenna side with non acetic cure outdoor weather grade RTV silicon.Point is, to cover all exposed metal parts for the N connector + the base N part.

author: kj7e
author_rank: Frequent Contributor
timestamp: April 28, 2018, 09:45:50 pm
content: N connectors themselves have a rubber seal which should prevent moisture entering, but there is always the possibility. Dont need to get crazy with it, just a bit of silicon to help seal the female N flange where it mounts to the antenna base and the screws. May even just pull a screw out one at a time and put a dab of RTV at under the head of the screw. Then run a small bead round the edge of the N flange. The coax wrap does a few things, it helps prevent moisture from entering from both the coax jacket and protects from oxidation and rotting near the connector. It also helps insure the connector does not come loose. With that in mind, just hand tighten the N.

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2018, 08:59:11 am
content: Quote from: kj7e on April 28, 2018, 09:45:50 pmAbout rotting and oxidation, these connectors should not be rusted right ?I'm not talking about no brand China made connectors, as I'm going to use Rosenberger N male, and judging from the antenna's side N female, Huber+Suhner's should be decent right ?

author: mc172
author_rank: Frequent Contributor
timestamp: April 29, 2018, 10:04:57 am
content: Quote from: kj7e on April 28, 2018, 09:45:50 pmThe rubber seal only prevents water getting into the centre. There is nothing stopping it getting into the cable. There are two ingress paths not accounted for by the rubber seal.The correct tightening torque for an N connector is about 1.5 Nm, which is a lot more than you can achieve with your hands. It's important to tighten them to the correct torque so that the series impedance of the ground plane is as low as possible. If it isn't very very low, you get leakage and may be susceptible to interference by external signals.

author: BravoV
author_rank: Super Contributor
timestamp: April 30, 2018, 08:35:41 am
content: Quote from: mc172 on April 29, 2018, 10:04:57 amAs this is just a hobbyist project, wonder what or how bad if its tightened by hand, say compared to using the right torque and of course the right tool for it.

author: mc172
author_rank: Frequent Contributor
timestamp: April 30, 2018, 11:58:37 am
content: My point is that it's not very good advice. It's hardly difficult to put a spanner or a set of grips on it. It would have been much better advice to have not mentioned tightening it in the first place.

author: CopperCone
author_rank: Super Contributor
timestamp: April 30, 2018, 02:49:40 pm
content: Im not sure how true this is. I have n connectors with diamond knurels on them that dont have any kind of surface a torque wrench can mate with. They are clearly designed to be used for hand tight operation.I do believe however that my n connectors rated for 18ghz operation all have nut patterns on them. I am not sure i have a knureled one that is 18ghz rated

author: mc172
author_rank: Frequent Contributor
timestamp: April 30, 2018, 03:14:37 pm
content: The giveaway is usually the presence of slits in the inside of the male N connector. If they're present, it's a "low frequency" version and probably has a knurled outer - but what frequency that is, I couldn't tell you. I haven't come across many that have the slits, yet have a nut.

author: BravoV
author_rank: Super Contributor
timestamp: April 30, 2018, 05:21:47 pm
content: Quote from: CopperCone on April 30, 2018, 02:49:40 pmQuote from: mc172 on April 30, 2018, 03:14:37 pmMy N male Rosenberger has knurled and nut shape like this, and recommended torque 0.7 Nm to 1.1 Nm.For sure my signal need, is only at 1575.42 MHz.Grabbed from Google