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Old 18-11-2014, 11:36   #1
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Pull VHF cable through mast

I am exchanging 2 RG58/U for 2 LMR-400 for VHF and AIS. The mast is about 70' long. It will be lieing down this Thursday.

It will be tight in the mast.
What is the best method to tie the pull line to the LMR-400.
What would be a good pull line? Would AMSteel 7/64 make a good pull line?
Would it be better to use the exisitng RG58/U as the pull line?
Any suggestions as to what kind of tape to use?

Thanks.
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Old 18-11-2014, 11:55   #2
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Re: Pull VHF cable through mast

Are you replacing the cable with a new one with the connector already on it? Single handed? If so then use a coax butt connector to join the old to the new and push the new one in. Have a person pulling gently on the other end. Or hang a pulley on the other end beyond the point of exit and run a line back to your self to pull with. Lube with mineral oil or baby oil or sun screen. Push in a wire hanger or something beforehand to check for spray-foam or zip-ties
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Old 20-11-2014, 12:15   #3
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Re: Pull VHF cable through mast

roetter,
Sorry I didn't see this until now (Thursday), as you're probably out trying to pull the cable as I write this!!

Just in case you're delayed and want some answers....here goes...

1) Although I'm a fan of low loss cable, understand that LMR-400 is a bit of overkill for most installs...
(Yes, I do have 35' of LMR-400uf, going to my stern-rail/back-up/AIS antenna....and have 25' of LMR-400uf from the mast base to the NAv Station, and 70' of LMR-240 up thru the mast....but I'm a fanatic about radio!!)

2) I hope you are referring to LMR-400uf (that's the "ultra-flexible" version of LMR-400), as trying to install regular LMR-400 is going to be a pain....not to mention I HATE the copper-clad alum center conductor for use near salt air!!

3) Any force used that requires pulleys/blocks, etc. or even a lot of elbow grease / grunting and pulling, etc. is WAY too much force to use to pull coaxial cable....
If you need to use that much force, you need:
--- a bigger conduit...(best and first choice...)
--- smaller cable...(LMR-240uf is great...)
--- cable lubricant...(and electrical supply house has wire/cable lube, designed just for this purpose.....it's cheap and easy to use....)



5) Specifics....
Quote:
Originally Posted by roetter View Post
I am exchanging 2 RG58/U for 2 LMR-400 for VHF and AIS. The mast is about 70' long. It will be lieing down this Thursday.
FYI, LMR-240uf has HALF the loss of RG-58....(3db/100' vs. 6.1db/100').....going further to LMR-400uf (at 1.5db/100') gains you only about 1db additional....

It will be tight in the mast.
Assuming you are talking about the typical in-mast wiring conduit, I doubt you'll be able to install TWO runs of LMR-400uf, in the same place as the two runs of RG-58....heck you may even find trying to run ONE length of the LMR-400uf to be tight....

As I wrote above do NOT attempt this with regular LMR-400, but rather use only the "uf" versions of LMR cables....such as LMR-240uf and/or LMR-400uf....

--- Whatever cables you do desire to run, the BEST overall way to do this is to pull out ALL the cable/wiring that is in the conduit that you are using.....keeping a strong double-braided pull string that is easy to tie knots in that stay tied tight (such as a 3/16" nylon or polyestser rope...I'd not recommend Dynemma)...

--- Separate all the individual cables, remove the RG-58 cables, and then with all the cables (including your two new pieces of coax) lying out straight, attach the largest/strongest one or two to the "pull string" with a few tight hitches and two very tight layers of 3M electrical tape....attach all the other wires/cables to this with two tight layers of 3M electrical tape...this way you have a sort-of long bullet-shaped group of wires/cables with the pull string coming out the small pointy end....

--- Have one person slide/guide the group of wires thru the mast conduit and the other person pulling them thru using the pull string....

The above procedure is exactly what I did with my mast wiring about 8 years ago....except that I replaced ONE length of RG-8x, with TWO lengths of LMR-240uf....(as there was NO way that two runs of larger cable was going to fit....I even tied to see if I could use one length or 400 and one of 240, but it would've been VERY tight and most probably I'd have damaged the coax trying to pull it / squish it that hard....)

--- If the group/bundle is a tight fit, use plenty of wire/cable lube, and she'll slide thru like butter!!!


What is the best method to tie the pull line to the LMR-400.
Tie a couple hitches and two layers of VERY tightly wrapped 3M electrical tape....

What would be a good pull line?
Use nylon or polyester, as you can tie a tight knot that will not slip....
Or, you could use a steel or plastic "fish tape" run thru the conduit, as a "pull string"....(all electrical supply houses have them....and I have one on-board my boat...)


Would AMSteel 7/64 make a good pull line?
No....a bit to slippery to tie reliably...

Would it be better to use the exisitng RG58/U as the pull line?
Since you almost probably will need to pull out everything from the conduit, obviously the RG-58 will no longer be in there to use....
But, in the off chance that you do try to pull the neew cables thru with other cables still in there (bad idea in my opinion), you would still want to pull out the RG-58 cables and have them pull in the pull string for you to use to attempt to pull thru the new cables....


Any suggestions as to what kind of tape to use?
Any good quality electrical tape that will stretch quite a bit (without breaking) and allow you to wrap cables very tight....
I recommend 3M / Scotch "33".....but there are many others that will do the job...

Thanks.


I do hope this helps....and again sorry that I didn't see this yesterday....

Fair winds and good luck...

John
s/v Annie Laurie
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Old 20-11-2014, 20:53   #4
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Re: Pull VHF cable through mast

Thanks for the very good information.

After all the talk about taking the mast down Lagoon is attempting to prevent the mast foot from moving by drilling larger holes for the 4 foot plate bolts and going up one size on the bolts.

Now I will have to pull cables while the mast is up.

I have to start thinking it over again.

But for now I have a Vesper splitter and will hook up the AIS and VHF to the better antenna/cable.


Rolf
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Old 21-11-2014, 07:02   #5
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Re: Pull VHF cable through mast

John is exactly right. I'm an RF engineer and advise the use of smaller cables like LMR240 for short VHF runs like a masthead antenna. The 1dB loss mentioned is insignificant in terms of actual performance over the air. People get way too caught up in the power loss numbers. I have been tempted to create a video injecting a weak signal into a vhf rig and stepping the strength by small 1-2dB increments to illustrate how small the difference really is.

One thing i do when pulling the new cable is to attach the pull line several feet back and tape together with the new line with tape all the way to the end. What you end up with is two lines wrapped in tape for a few feet. This keeps the thickness low and distributes the strain along the entire length where the cables are taped to each other. As you pull, don't force it too much if it binds, Back it out some and try again. There is a type of lubricant used by electricians just for pulling wire through conduit and is designed to not react with the outer shield. I'd be careful about using mineral oils and other lubricants not designed to be safe on the plastic outer shield.

I always mention it, but it is the most common failure. Weatherproof the exposed connectors. Electrical tape will work for a few months, but isn't a good long term solution. A better method is electrical tape, followed by butyl tape, wrapped again in electrical tape. This is a common method use by professionals. There are other sealants that work fine, but many of us have some of Maine Sail's butyl tape on hand and is pretty cheap and effective.

Lastly, buy a crimp tool for whatever cable you decide on and use crimp on connectors, not those screw on clamp type made by shakespeare. Solder on pl259's are difficult to solder properly and hard to tell if you did it correctly. A low priced crimper can be bought on Amazon for about $35, and some have interchangeable dies for different cables.

Good luck if you haven't done this yet.


Sent from my iPhone using Cruisers Sailing Forum
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Old 21-11-2014, 11:56   #6
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Re: Pull VHF cable through mast

Ah, good post and replies. I'm planning the same work in February. Quite timely and appreciated
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Old 21-11-2014, 12:31   #7
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Re: Pull VHF cable through mast

Quote:
Originally Posted by El Rubio View Post
J............. There is a type of lubricant used by electricians just for pulling wire through conduit and is designed to not react with the outer shield. I'd be careful about using mineral oils and other lubricants not designed to be safe on the plastic outer shield.............
Agreed, 100%. You can buy it at your local home center or hardware store in the electrical department. Other "lubricants" (I can't believe someone suggested suntan lotion) can either damage the insulation on the wires or dry and glue the wires in place preventing future repairs.

Pulling wires was part of my job for many years.
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Old 21-11-2014, 14:13   #8
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Re: Pull VHF cable through mast

I recommend you use an electricians "pull sock" I can't think of the real name of the product but it is a mesh sock that crimps down on the cable as it is pulled. Labor Saving Devices Pull-Zitâ„¢ 1/4" Diameter Mesh Pull Sock for Double RG6 Cables | 85-902 (85902) | Labor Saving Devices Really handy to have on board for those pulls.
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Old 21-11-2014, 15:06   #9
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Re: Pull VHF cable through mast

Quote:
Originally Posted by Charlie View Post
I recommend you use an electricians "pull sock" I can't think of the real name of the product but it is a mesh sock that crimps down on the cable as it is pulled. Labor Saving Devices Pull-Zitâ„¢ 1/4" Diameter Mesh Pull Sock for Double RG6 Cables | 85-902 (85902) | Labor Saving Devices Really handy to have on board for those pulls.
I would use this:



Several sizes are available at home centers and such. I used them on the job.

Klein Tools 1/2 in. Pulling Grip-KPS050SEN at The Home Depot

It's like the old Chinese finger pulling toy.
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