Ruggedized and Load Rated Coax?

BMDaug

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Hey everyone, does there exist a ruggedized coax capable of directly carrying load in a situation where the antenna is hanging from the coax? I have a dipole that’s just under a pound and I’d like to have the option to temporarily suspend it from the coax in a field operating scenario. I realize that it may require special connectors etc. but does such a thing exist?

Thanks everyone,
Brian
 

RFI-EMI-GUY

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Not ideal, but why would you put the connectors under that strain? Make some way to offload the stress to the cable if the load is small. Some cable ties and eye loops? You can also buy plasticized stainless steel wire rope at Home Depot that you can use as a support for the cable and antenna. I have used this for supporting coaxial cables on a five section retractable tower.
 

BMDaug

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I realize that it’s not ideal for standard coax and connectors to be subjected to this sort of strain. I’m just wondering if there is something purpose built for an application like this. I suppose I could use parachute cord and rig something that way!

Thanks,
Brian
 

mmckenna

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I realize that it’s not ideal for standard coax and connectors to be subjected to this sort of strain. I’m just wondering if there is something purpose built for an application like this. I suppose I could use parachute cord and rig something that way!

Thanks,
Brian
If you look at the specifications for good name brand coax, you'll see tensile strength listed. Real (not Chinese knock off) Times-Microwave LMR-240 has a tensile strength of 80 pounds: https://timesmicrowave.com/DataSheets/CableProducts/LMR-240.pdf

Connector installation will impact this. The cable may hold 80 pounds, but a poorly installed connector may fail at much less.

I've got a site at work where we had to run two sections of 1-5/8 inch Heliax up a mechanical chase. It runs about 5 floors. There is only access at the top and bottom. There is a Kellum grip installed at both the top and the bottom that the cable hangs on. These are spec'd/supplied by the manufacturer exactly for this sort of installation. The cable weighs about 1 pound per foot, so a considerable amount of weight on those grips. And it's been there since 1994 without any issues. But this is 'hardline' coax, and it's much more rugged than standard braided coax.

So, yes, it can be suspended, -IF- you do it correctly. A small antenna won't be much of an issue. Key is properly installed coaxial connector, and maybe adding a separate support rope.

As for ruggedized. Yes, they exist. But they get expensive. For what you are doing, I don't think you need something at that level. Just use high quality coaxial cable. Make sure your coax connectors are installed correctly. Use adhesive lined heat shrink over all the connector crimps.

Unless you have a pet chimpanzee that likes to swing from your antennas, you should be just fine with regular off the shelf cable. Looking at some of the hammy installs I see, there's a lot of loose/floppy cables hanging from beam antennas, masts, etc.
 

W0JOG

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As I've urged before, buy a copy of the American Radio Relay League's "Amateur Radio Handbook" and read it. You'd be amazed at how much it will tell you about the hobby of "amateur" radio and how to think out your own version of solving problems. If there is no other amateur anywhere near you to answer your questions.

de W0JOG
 

BMDaug

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As I've urged before, buy a copy of the American Radio Relay League's "Amateur Radio Handbook" and read it. You'd be amazed at how much it will tell you about the hobby of "amateur" radio and how to think out your own version of solving problems. If there is no other amateur anywhere near you to answer your questions.

de W0JOG
I actually just received my copy a few days ago…

Thanks,
B
 

BMDaug

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This is just an inquiry about available products. There are so many products available these days that’s I find it’s better to pose an open question than to read a book or even do a Google search. There are many people here who have experience with certain specialized applications that know about specialty products they have used in the past.

In this case, I’m trying to hang a vertically polarized dipole for search and rescue applications. Isn’t that what this forum is for? Learning from other people’s experiences?

Regards,
Brian
 

W0JOG

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My suggestion was that you are over-researching. Just pick your coax from what-ever you have and try it. A SO-239 mounted to a stout piece of plexiglass or other plastic and you'll soon know an answer you will remember. That is what "amateur radio" is all about, it has been my observation over some 60 years as a ham.

As for "Search and rescue," Hams in S&R are likely serving effectively as a backup to public service units they've made friends with. Our forte would be long range communication rather than VHF/UHF. For that, a horizontal dipole likely would serve best. After a well-outfitted mobile rig, which was the reason amateur radio license plates were originally agreed to by the law. They would identify the ham who would have set up his mobile. For 24 years, I drove a GMC conversion van to which I'd installed capability from 160 meters to 440 MHz. And, later, 180 watts of solar panel and microwave, refrigerator and my capability to be there and reaey for as long as needed. Had you thought that through?

de W0JOG
 
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BMDaug

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My suggestion was that you are over-researching. Just pick your coax from what-ever you have and try it. A SO-239 mounted to a stout piece of plexiglass or other plastic and you'll soon know an answer you will remember. That is what "amateur radio" is all about, it has been my observation over some 60 years as a ham.

As for "Search and rescue," Hams in S&R are likely serving effectively as a backup to public service units they've made friends with. Our forte would be long range communication rather than VHF/UHF. For that, a horizontal dipole likely would serve best. After a well-outfitted mobile rig, which was the reason amateur radio license plates were originally agreed to by the law. They would identify the ham who would have set up his mobile. For 24 years, I drove a GMC conversion van to which I'd installed capability from 160 meters to 440 MHz. And, later, 180 watts of solar panel and microwave, refrigerator and my capability to be there and reaey for as long as needed. Had you thought that through?

de W0JOG
I really appreciate your help because you are challenging me to engineer more and spend less. Please don’t misinterpret my reply as diminishing your advice! I apologize if that is how I came off.

For us, SAR is mostly pulling people out of remote places that have hiked, climbed or ridden in and then fallen or gotten themselves lost or stuck. Most of these situations are resolved in less than 24 hours. SAR here is a fairly large organization with dozens of members and many SAR owned vehicles including trucks, snow mobiles, atvs, side by sides, and ebikes. One of the issues we are up against is coverage. We use VHF and 7/800. The idea for this project is to be able to get coverage temporarily to places that may be inaccessible to vehicles with equipment capable of bridging that gap in coverage. This rig is capable of operating on all bands and can be easily transferred between necessary forms of transportation for that mission, or taken on foot to the location of the incident.

I’m currently working on my personal off-road vehicle, which will be able to accept this system and will also include an HF radio and sustain me for longer periods in disaster relief situations, but that’s phase 2 lol. Phase one is to meet the current need for comms on the primary SAR bands and to work from there.

Thanks for your help and insight!

-Brian
 

W0JOG

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No need to apologize. I just responded in ham-think and included the extra for your mental files. For the ranges and needs you describe, I'd rely on a 5/8 wave vertical which will give you working coverage for all you describe, it is my experience.

de W0JOG
 

BMDaug

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Thanks for the input everyone! I ended up creating a holster for the antenna. A couple of neoprene washers, a couple of o-rings, and some parachute cord and I’m in business. Now I can just throw some cord over a limb and hoist it up. The coax will hang down and can be used to adjust basic directionality/elevation. I appreciate the inspiration!

-B
 

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W0JOG

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On a dipole, you want to hold the coax out at a horizontal angle away from the radiating elements for some distance, at least a few feet, if you can to get the impedance match as good as possible.

de W0JOG
 

BMDaug

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On a dipole, you want to hold the coax out at a horizontal angle away from the radiating elements for some distance, at least a few feet, if you can to get the impedance match as good as possible.

de W0JOG
Right, but it’s effectively an end-fed dipole, or at least the connection is at the end and the entire thing is self contained. It’s designed to connect directly to a radio or be used on a mount. The larger models are designed to be used on ships and they recommend connecting the antenna to a mast and running the wire down the mast, so not 90 degrees from the antenna. It is ground plane independence however.

I thought that only applied to a center-fed, more traditional dipole so that the coax doesn’t run up against one half of the dipole… The antenna is completely sealed and the connection is on one end. Using the analyzer, the impedance matches well regardless of feed line position, and also matches fine if there is no feed line at all and the antenna connects directly to the analyzer. 🤷🏼‍♂️

-B
 

mmckenna

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I thought that only applied to a center-fed, more traditional dipole so that the coax doesn’t run up against one half of the dipole… The antenna is completely sealed and the connection is on one end. Using the analyzer, the impedance matches well regardless of feed line position, and also matches fine if there is no feed line at all and the antenna connects directly to the analyzer. 🤷🏼‍♂️

-B
You are correct. I have a few end fed dipoles that we used on our 800MHz Motorola portables. They are designed to be end fed/mounted on top of the radio.
Suspending by the coax will work fine.

If you were building a dipole that was center fed, then yes, you would want to feed from the center and take the coax off at a 90º angle.
 

W0JOG

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End fed dipole? Never heard of such a thing. An end-fed antenna is likely a loaded element and uses the coax feeding it, if there is one, as the counterpoise. Or the case of the radio if there isn't.

de W0JOG
 

mmckenna

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