Need advice on N9TAX

[Murphy625]

I have an N9TAX antenna and need to haul it up 50 feet into a giant maple tree.. I ordered the antenna without the coax extension cable they offer so I could just attach some of my Columbia RG8/U (.405 diameter) to it.

The RG8/U is much better at VHF and UHF frequencies than the RG58 that is offered.

Anyhow, I'm a bit worried about the weight of 50+ feet of the RG8/U and don't want to pull the N9TAX antenna apart.

Should I be concerned about 50 feet of coax hanging from the antenna? I can use some polypro baling twine and remove the stress from the antenna if needed.

 

[DJ11DLN]

His website shows using ladder line, which would I think be a good bit lighter. And there's always LMR-240.

http://www.n9tax.com/slim jim info.html

 

[mmckenna]

Not only is it the antenna that could be damaged by the tension, but the connectors on the coaxial cable.

You need to provide some strain relief to keep the tension off the antenna and the connectors. That might mean anchoring it to the tree (leave some slack to allow the tree to move/grow) or attach the coax to a rope and let that take the strain.

 

[Murphy625]

His website shows using ladder line, which would I think be a good bit lighter. And there's always LMR-240.

Slim Jim Info

The ladder line IS the antenna.. its fed with coax.

I will be pulling my antenna up 50 feet into a tall maple tree so it will be dragging 50 feet of RG8/U coax with it. The 50 ft of RG8/U coax weighs around 5.6 lbs, and then there's the friction of it interacting with branches as its pulled it up.

I'm not sure if its required, but what I did was to cut a 6 foot piece of orange polypro baling twine. I created a loop at the top end for attaching the pulling rope to. I then attached the top of the antenna to a heavy duty rubber band and tied the other end of the rubber band to the poly twine loop.

I fed the twine through the antenna ladder holes in and out so the line is weaved into the antenna and then secured the twine to the RG8/U coax with some zip ties and electrical tape.

This way, the stress of pulling the antenna up the tree is transferred from the pulling rope, down the baling twine, and into the coax. The only stress the antenna should see is that from a rubber band which keeps it stretched out.

The rubber band should act like a fuse.. if too much stress gets put on the antenna, the rubber band should snap.

The antenna will not be outdoors for more than a day or two so there shouldn't be any issues with the rubber bands degrading.

 

[Murphy625]

Not only is it the antenna that could be damaged by the tension, but the connectors on the coaxial cable.

You need to provide some strain relief to keep the tension off the antenna and the connectors. That might mean anchoring it to the tree (leave some slack to allow the tree to move/grow) or attach the coax to a rope and let that take the strain.

Didn't see your post right away.

Thank you. I have used some orange polypro baling twine (very strong stuff @ 1/8 diameter) to take the strain off the antenna and transfer it to the coax jacket. The RG8 Coax is now pulled up by its own jacket and the antenna above it has only a small amount of tension from a rubber band to keep it straight.

I wrapped the baling twine around the RG8 in a barber-shop type spiral and secured it with a couple of zip ties and then electrical taped the entire thing The 6 feet or so of twine above the RG8 coax just keeps the N9TAX antenna from getting all curled up.

This is only a temporary setup to last an hour or two and then it comes back down.

 

[mmckenna]

Sounds like that will work just fine.

I've got an installation at work that has two runs with about 120' vertical rise up a mechanical chase in the building. 1 5/8" heliax, so it's pretty heavy. The coax is supported using grips from near the top. Similar to this:
https://www.rfparts.com/rfpartssurplus/l5sgrip.html
Sounds like you've done something similar with the polypropylene line.

 

[Murphy625]

Sounds like that will work just fine.

I've got an installation at work that has two runs with about 120' vertical rise up a mechanical chase in the building. 1 5/8" heliax, so it's pretty heavy. The coax is supported using grips from near the top. Similar to this:
https://www.rfparts.com/rfpartssurplus/l5sgrip.html
Sounds like you've done something similar with the polypropylene line.

I've used hundreds of those strain relief meshes.. never seen one small enough to fit RG8.. not saying they don't exist, I've just never seen one.

I always used them on power or signal cord coming out of machinery control panels.. I think the smallest I've ever used was on 10ga 4 wire SO cord, which is about 3/4 inch diameter.

The other thing I'd be a bit concerned about in my application is putting anything metal near the N9TAX antenna.. From what I understand, they can get screwed up (swr?) just hanging them close to metal window frames or doors.

After building a fishing reel / slingshot launcher, a whole new world is opening up!

 

[K4EET]

<snip> The antenna will not be outdoors for more than a day or two so there shouldn't be any issues with the rubber bands degrading. <snip to the next post> This is only a temporary setup to last an hour or two and then it comes back down.

Murphy625, may I ask why this is a temporary installation? What are you trying to measure? As for the RG-8/U, are you aware that there is RG-8X (miniature RG-8) that is about half the size of RG-8/U but has similar characteristics? Even though RG-8X has more loss, the weight trade-off and flexibility of RG-8X may make it better to use. If you are just going to make some receive signal measurements, you have the specs on both types of cable for comparison purposes.

The slingshot/fishing reel method of getting a line up into the tree is great. That is what we use around here although one guy does have a spud/tennis ball compressed air gun which is more accurate that we sometimes use. Here is one of many websites about antenna launchers. Pneumatic Antenna Launchers Let me know if you set out to build one...

73, Dave K4EET

 

[Murphy625]

Murphy625, may I ask why this is a temporary installation? What are you trying to measure?

I'm trying to create a portable antenna that is easy to deploy and can "reach out and touch someone" without the need for repeaters. A true stand-alone system that can go wherever I can. The area I live in is very hilly.. no mountains or anything, but we do have elevation changes that can vary 40 or 50 feet.. it creates problems for the higher frequencies as I've learned with all the antenna software I've been screwing with. I learned a lot playing with the antenna software stuff lately.

As for the RG-8/U, are you aware that there is RG-8X (miniature RG-8) that is about half the size of RG-8/U but has similar characteristics? Even though RG-8X has more loss, the weight trade-off and flexibility of RG-8X may make it better to use. If you are just going to make some receive signal measurements, you have the specs on both types of cable for comparison purposes.

Eventually, I will be transmitting.. I'm just not there yet.. but I'm close! I took a practice "General" test this week on one of those websites.. I didn't pass, but I did notice that my wrong answers were mostly on arbitrary questions and not the ones based on physics. For instance, when they asked about SWR, impedance or grounding, I got those questions correct, but when asked about the rules and regulations, I missed on those questions. At least I know where to focus my study now.
I pass the practice tests for technician every time but plan on taking both tests when I go.

The RG8X has almost almost twice the loss as compared to RG8/U, and at a 50 foot run up a tree, I think it becomes somewhat significant from the limited knowledge I have about this stuff. Its not so bad at lower frequencies, but at 144 and 440, it gets bad really fast. In fact, it gets stupid at 440.

Because of the terrain, I have to be able to punch through the tops of trees and not have my signal evaporate on the other side.
Which brings me to another question.. Would VHF go further in the winter due to the lack of foliage or would the higher air density counteract that benefit?

The slingshot/fishing reel method of getting a line up into the tree is great. That is what we use around here although one guy does have a spud/tennis ball compressed air gun which is more accurate that we sometimes use. Here is one of many websites about antenna launchers. Pneumatic Antenna Launchers Let me know if you set out to build one...

73, Dave K4EET

Ya, I didn't come up with it on my own.. thanks goes to youtube for that. I considered the air cannon but its less portable than a slingshot. I put a 20lb line with a 1oz lead weight over a 100 foot maple tree with room to spare... any more power and I'll have to file a flight plan! Its scary how well that works using such old school tech.

 

[ParanoidAndroid]

Like one of the other posters mentioned, you can half hitch some jet line to your coax feedline, below the connector, so you don’t damage it. I use a mono band vhf n9tax, and 1/2” heliax to feed it. I throw the line up, and weave it down through the slim jim without tieing the line directly to it. Then once you hoist it up a bit, tied to to coax, tie a small piece from the top of the slim jim to the main line to keep it from sagging back down. Because that mono band slim jim is so easy to hoist up my palm tree, it kills any other antenna I can get up, unless I were to errect a tower, or push up mast of some kind... This also works great while portable.