Crimp Connectors

[mmckenna]

So the Times site says these connectors use "Inner Contact Attach: Spring Finger". Are they not reliable or something? Is there a compelling reason to go with the solder-on centerpin types instead?

The EZ connectors work just fine. I've installed a bunch of them without any issue. I haven't been through the 'official' training to install them, but still, they've worked fine for VHF, UHF and 800MHz work.

The only drawback to them is you need to have the prep tools, and that turns some people off. If you are doing a bunch of these connectors, then the tools make financial sense. Important part of the install kit is a tool that bevels the outer edge of the center conductor and helps it slip into the center pin correctly. You could maybe cheat this by using a small file. Not beveling the center conductor is what usually screws up the install.

 

[Indie]

Thanks for the great info!

The only drawback to them is you need to have the prep tools, and that turns some people off. If you are doing a bunch of these connectors, then the tools make financial sense. Important part of the install kit is a tool that bevels the outer edge of the center conductor and helps it slip into the center pin correctly. You could maybe cheat this by using a small file. Not beveling the center conductor is what usually screws up the install.

If you have real Times LMR400, not another brand and not stranded center conductor, those are the very best connectors available. My 8yr old grand daughter can install one in a minute and it will sweep perfect to at least 6GHz. A lot of seasoned professionals can't install a connector with solder pin that will sweep ok to 6GHz, it starts to get very critical above a few GHz.

Ok so now we are getting into the cable issue out of necessity because I shouldn't be picking connectors without first being sure I am using the right cable. I am doing a typical house install on a home mounted mast. Either through the attic wall and down the inside of the wall to the basement or down the outside of the house behind the siding and in just above the foundation. Both entry spots have preexisting coax cable holes where the RG6 was. I hear LMR400 is a little stiff. But then some say you can stuff it anywhere just like RG6? Plus I want something I could lay on the ground or bury so I could put an antenna in my yard if need be; in the very least I need to test the reception of the antenna I have before I put it up on the mast. I have an MP Antenna 08-ANT-0861 25-6000MHz. The bulk of my scanner listening is below 1000MHz. But I do like to explore around higher freqs using SDR. And at some point I want to get licensed so I can transmit and have something fun to do with my kids. I don't need perfection but I don't want to save 25 or 50 bucks and have something that performs like a rubber ducky.

So all that being said: what would be the appropriate cable for my needs? Please pardon my ignorance and thank you so much for the info!

 

[mmckenna]

Wait, I thought you already had the LMR-400 installed?

You point out a couple of different types of installs that may not use the same type of cable. That changes things.

For any cable installation below grade/buried you need to use a suitable direct bury rated cable. Even if it's in conduit underground.
You can get LMR-400DB, and it uses the same Times Microwave LMR-400 connectors.
But it adds to the price of the cable.

For non-buried installation, you can use standard LMR-400.

For any external antenna, you need to have lightning protection installed where the coax enters the home. You also need proper grounding.

LMR-400 is stiff cable and it's not going to route the same way as RG-6. The bend radius for LMR-400 is about 4 inches, so it's going to stick out a bit from the wall. You'll need a larger hole, about 1/2 inch.

We should probably take a step back and get some clarification about what you exactly have in your possession right now. LMR-400 is not the be-all, end-all cable. It's good stuff for hobby use, but depending on the length of the cable run, it may be overkill, or it may not be enough. Add in the complexities of connector installation, and it can increase cost and difficulty.

There's multiple ways to approach this installation. Running a continuous length of LMR-400 from your antenna to your radio is NOT what you want to do in any installation. You do need a lightning suppressor where the cable enters the home, and that may be a good point to switch to a smaller cable to run into the home. You also don't want to connect LMR-400 direct to your radio. Since it's stiff and heavy, it can damage antenna jacks on your radios.

 

[WB9YBM]

Is there a compelling reason to go with the solder-on centerpin types instead?

crimped connections, since they are not air-tight, allow a certain amount of humid air in causing corrosion. Over several decades of dealing with that--having corrosion cause a degradation of electrical conductivity in an otherwise (mechanically) sound connection--I try to avoid crimp connections whenever possible. (and if I need extra mechanical support for some reason, I'll look for other ways of doing it.)

 

[prcguy]

A properly crimped connector is superior in all ways to a solder connection. In the aircraft industry solder cable connections are prohibited and must be crimped. I've made a huge comm and computer cable harness for an aircraft and was surprised at the rules but had to follow them. No solder anywhere partially because of vibration and solder wicked into stranded wires will weaken the wire and make it more susceptible to failure. All crimp tools had to be periodically inspected and certified. All connector pins had to be pull tested and certified after crimping, etc.

And I was mil spec solder certified and was also at inspector level for soldering and still could not solder a single connection in an aircraft harness.

crimped connections, since they are not air-tight, allow a certain amount of humid air in causing corrosion. Over several decades of dealing with that--having corrosion cause a degradation of electrical conductivity in an otherwise (mechanically) sound connection--I try to avoid crimp connections whenever possible. (and if I need extra mechanical support for some reason, I'll look for other ways of doing it.)

 

[WB9YBM]

A properly crimped connector is superior in all ways to a solder connection. In the aircraft industry solder cable connections are prohibited and must be crimped. I've made a huge comm and computer cable harness for an aircraft and was surprised at the rules but had to follow them. No solder anywhere partially because of vibration and solder wicked into stranded wires will weaken the wire and make it more susceptible to failure. All crimp tools had to be periodically inspected and certified. All connector pins had to be pull tested and certified after crimping, etc.

And I was mil spec solder certified and was also at inspector level for soldering and still could not solder a single connection in an aircraft harness.

humm...both the aeronautical as well as military comms I worked on were all soldered. Although, that's going back a few years. Thanks for the update on new techniques!

 

[majoco]

What prcguy said +1 - and I've wired more than a few aircraft with passenger entertainment systems which all used SMA connectors and every one was crimped including the centre pin. We only used AMP tools and jaws with a current calibration sticker which were signed back in to the tool stores at the end of the shift where they were tested with go-no go gauges - even if the guys on the next shift were going to sign them out again - no passing the tools over to your mate untested. Every six months they went to calibration section for a full test and re-certification. The cost of tooling and testing is insignificant compared to grounding the aircraft for for repairs on a no-go system. Now that the public address system is routed through the passenger headphones, one seat system failure will ground the aircraft.

 

[prcguy]

My aircraft harness job was around 1994 and not that new. Individual components can have soldered connections but the wiring that lives in the aircraft is crimp only. My crew of about 6 people spent 6 months building the harness spending 40hrs a week. It was real expensive but not that big or impressive looking when all laid out on a warehouse floor. We all looked at it and thought "there sits 6 months of our lives crimping?"

This might be the same plane I made the harness for and at the time they cut off the nose of the aircraft and grafted on the nose of an F-15 for testing a new radar system. I think its the same aircraft based on the external cable conduit spanning the cockpit to the middle of the aircraft which is not on a regular A-3. All the cables in that conduit were wrapped in a very cool but expensive RF EMI absorbing blanket.

I'm not saying this job was any more important than your hamster hobby connector installs, but it did get me a free Navy pilots jacket as a thank you for a job well done.

humm...both the aeronautical as well as military comms I worked on were all soldered. Although, that's going back a few years. Thanks for the update on new techniques!

 

[Indie]

Wait, I thought you already had the LMR-400 installed?

No I have not purchased the coax yet.

You point out a couple of different types of installs that may not use the same type of cable. That changes things.

I am almost certain that when I get the antenna up on the mast I want to run the new wire down the outside of the house and in though a hole in the wood just above the concrete foundation. This is the easiest option. I really not want to spend hours fishing it through the walls. So a considerable amount of wire will be outside. So its got to be flexible enough to stuff it behind the siding, standard vinyl siding. But before I get the antenna up on the mast I want to make sure its working by just mounting it on PVC pole in the yard so some coax will be laying in the yard (possibly superficially buried) for a while in the northern New York winter.

For any external antenna, you need to have lightning protection installed where the coax enters the home. You also need proper grounding.

I am going to (unless you suggest otherwise?) ground to NEC specs using the instructions here:

How I Grounded My Outdoor Antenna

Whether metal or plastic, your TV antenna should be properly grounded. Read on to find out how to do this, and even install a little coaxial cable.

www.groundedreason.com

We should probably take a step back and get some clarification about what you exactly have in your possession right now. LMR-400 is not the be-all, end-all cable. It's good stuff for hobby use, but depending on the length of the cable run, it may be overkill, or it may not be enough. Add in the complexities of connector installation, and it can increase cost and difficulty.

There's multiple ways to approach this installation. Running a continuous length of LMR-400 from your antenna to your radio is NOT what you want to do in any installation. You do need a lightning suppressor where the cable enters the home, and that may be a good point to switch to a smaller cable to run into the home. You also don't want to connect LMR-400 direct to your radio. Since it's stiff and heavy, it can damage antenna jacks on your radios.

I have not purchased any new coax yet, but I have the antenna (MP 08-ANT-0861). Currently I have about 20 feet of RG8X coming from my little magnet mount whip that sits on on a steel table in the yard. This goes into the basement where it meets an RG58 patch (I think its 18 feet? gets around the room with feet to spare) to my scanner or computer dongle. I want to continue to use the patch for now at least. So to get the most out of my new antenna I want to run low loss cable from the antenna into the house where it can be patched with the floppy Davis RG58 patch.

Thanks so much!

 

[mmckenna]

OK, good deal.

So, LMR-400 is good stuff for hobby use and your length would not be too long for it. It should provide good performance, and if you decide to get your amateur radio license, it'll work fine for that.

The grounding link is pretty good, but you'll want to invest in a better grounding block that the one they show. Those are fine for cable TV/TV antenna/Satellite TV, but for any sort of transmitting use, you need one designed for it. Polyphaser is a good brand and I use a lot of those at work. You can get cheaper hobby/amateur grade protectors and save a few bucks and they should work just fine.

Only beef I have with the grounding tutorial is that if your electric utility entrance is not directly under your antenna, you'll absolutely want to add a ground rod directly under it. The idea is that you want to give any energy as straight and short a path as possible to ground. NEC then requires that the new ground rod and the existing ground rod be bonded together. Fairly easy to do, but will take some planning.

Here's what I would recommend:

Order whatever length of Times Microwave LMR-400 you need to get from your antenna down to the entrance point. Add a foot or two to create a drip loop before you connect to the protector. It'll cost a few bucks extra, but having them install the connectors is a good idea, they should have the correct tools and should test the cable after putting the connectors on.

These guys are a reputable shop: https://www.theantennafarm.com/catalog/times-microwave-lmr-400-1471
Get a male N connector on each end of the cable. Pay the extra few bucks for the 'heat shrink tubing'. That puts a layer of heat shrink tubing with a hot melt adhesive on the inside over the connector crimps. That helps with strain relief and is well worth it.
You'd be looking at around $70 for 35 feet of cable with heat shrink and two N connectors installed. Expensive, yes. But you'll get a good cable that will last you a long time and will work well when you get your amateur radio license. Running the cable exposed down the wall isn't an issue. The cable is designed for outdoor use, so no need to run it inside the walls.

You'll need the lightning suppressor: https://www.theantennafarm.com/catalog/times-microwave-lp-btr-nms-5979
You will need to mount that at the point the where you enter the house. Connect the cable from the antenna to it, but make sure you leave a 'drip loop'.

You absolutely need to waterproof -all- your outdoor connections. Skipping this step is a rookie mistake that will result in water getting in the coax and destroying it. https://www.theantennafarm.com/catalog/commscope-221213-1956 Those kits are a good deal and if you follow the installation directions, you'll have a waterproof outdoor connection. Don't let anyone tell you that you do not need it, you do.

From the lightning suppressor, you can use a smaller cable to get through the wall. Ideally you'd want to keep it a good low loss cable if you can. Drilling a large enough hole to get LMR-400 through is a good idea. If you absolutely cannot do that, then at least use something like LMR-240. Again, make sure you put in a drip loop to keep water from following the cable into the home.

You'll of course need a ground rod, ground clamps for both rods, and suitable cable. That sort of stuff can be had from Home Depot.