I am getting ready to install a fixed mount VHF radio and run a coax to a 3 ft. antenna at the top of my 28 ft. aluminum mast. I want to enter the mast at the bottom and exit at the top. Are there any pitfalls I should look out for, or recommendations on drilling and/or size of holes. I plan to use RG 8X for ease of routing the cable and having minimal loss, with clam shell covers at the entry points. Any good ideas/suggestions would be appreciated. Bill
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Geof
Internal Cable slap
Coax runs internally in my mast for the VHF and cell antennas. The previous owner is an "antenna guy" - he really understands them well. I love having the antennas up high, but I am sometimes bothered by the coax slapping inside the mast in an anchorage. I hope to remedy this soon, I have two ideas, I'm not sure which one I'll try first. One is to slide some pieces of foam into the mast to hold the cables taught. A piece at the top and the bottom. The other is to put wire-ties on the wires and leave the tails on them. Hopefully the plastic ties will help to suspend the wires in the mast and give me the seperation I need from the walls of the mast to cut down on the slap. I was thinking that I would need to space them out about every 4 feet or so and I would need to put three or four wire ties at each point, each tail facing a different direction. If I use three, each tail will be 120 degrees from the next one, if four wire ties, the tails will point out at 90 degrees from each other. Any comments? Geof
Coax runs internally in my mast for the VHF and cell antennas. The previous owner is an "antenna guy" - he really understands them well. I love having the antennas up high, but I am sometimes bothered by the coax slapping inside the mast in an anchorage. I hope to remedy this soon, I have two ideas, I'm not sure which one I'll try first. One is to slide some pieces of foam into the mast to hold the cables taught. A piece at the top and the bottom. The other is to put wire-ties on the wires and leave the tails on them. Hopefully the plastic ties will help to suspend the wires in the mast and give me the seperation I need from the walls of the mast to cut down on the slap. I was thinking that I would need to space them out about every 4 feet or so and I would need to put three or four wire ties at each point, each tail facing a different direction. If I use three, each tail will be 120 degrees from the next one, if four wire ties, the tails will point out at 90 degrees from each other. Any comments? Geof
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John Dawson
Wire slap
What I used on a smaller 24' mast were those kitchen scrubbers, the balls of plastic wire mesh you use to knock stuff off pots and pans. Ran the wires thru them at frequent intervals with a light line to maintain spacing. The diameter was about right. Not for internal halyards, obviously.
What I used on a smaller 24' mast were those kitchen scrubbers, the balls of plastic wire mesh you use to knock stuff off pots and pans. Ran the wires thru them at frequent intervals with a light line to maintain spacing. The diameter was about right. Not for internal halyards, obviously.
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joe phibbs
Why Not The Good Stuff?
Why don't you use the RG8 regular size coaxial cable? Line losses are substantially less. Yes, it may be a bit more trouble to wrestle into the hole, but not impossible. That stuff won't rattle at all and you will have the power-handling capablilities of much better wire. Be careful not to bend it too far and you should be fine. Joe
Why don't you use the RG8 regular size coaxial cable? Line losses are substantially less. Yes, it may be a bit more trouble to wrestle into the hole, but not impossible. That stuff won't rattle at all and you will have the power-handling capablilities of much better wire. Be careful not to bend it too far and you should be fine. Joe
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Bill
Good Suggestions
I appreciate the good suggestions. I have a couple of halyards that need to share the space so the plastic ties seemed to be a good idea. You are right about the RG8 being less lossy and I like the idea of the RG8 not rattling around inside the mast. I thought the RG8 might be a problem in negotiating a bend (don't know yet what the bending radius is for RG8) through a clam shell at the top of the mast. Also don't know if 90 degree connectors are available that would work at the upper entry point or if much additional loss would be incurred with the use of the additional connectors. I will check it out further though. Thanks much
I appreciate the good suggestions. I have a couple of halyards that need to share the space so the plastic ties seemed to be a good idea. You are right about the RG8 being less lossy and I like the idea of the RG8 not rattling around inside the mast. I thought the RG8 might be a problem in negotiating a bend (don't know yet what the bending radius is for RG8) through a clam shell at the top of the mast. Also don't know if 90 degree connectors are available that would work at the upper entry point or if much additional loss would be incurred with the use of the additional connectors. I will check it out further though. Thanks much
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Geof Tillotson
John, I like the scrubbie idea
I bet that's an idea that the manufacturers never thought of for their product. How long ago did you "make the fix"? I wonder how long the little plastic buggers will last, or if they'll get brittle. I know that wire ties get brittle after awhile when exposed to heat and sunlight. That's one of my thoghts/concerns since I only plan to take the mast down ever few years or so. Geof s/v Day-O
I bet that's an idea that the manufacturers never thought of for their product. How long ago did you "make the fix"? I wonder how long the little plastic buggers will last, or if they'll get brittle. I know that wire ties get brittle after awhile when exposed to heat and sunlight. That's one of my thoghts/concerns since I only plan to take the mast down ever few years or so. Geof s/v Day-O
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John Dawson
scrubbies aren't talking
gee, its maybe seven years ago and I have never had any mast noise. I haven't removed them so I don't know what condition they are in. The mast spends an equal amount of time aloft and down (trailer). To support the weight of the wire bundle inside the mast, the wires are led around a large thimble and seized like an eye splice; the thimble sits on the thru-pin for the shrouds at the masthead. the wires then bend upward into an AquaSignal multi-light. On top of the Aqua, there is a Windex, and a tiny Windex Light. If you are using a flashlight at night or guessing in the dark, get one of these lights. They are so perfect.
gee, its maybe seven years ago and I have never had any mast noise. I haven't removed them so I don't know what condition they are in. The mast spends an equal amount of time aloft and down (trailer). To support the weight of the wire bundle inside the mast, the wires are led around a large thimble and seized like an eye splice; the thimble sits on the thru-pin for the shrouds at the masthead. the wires then bend upward into an AquaSignal multi-light. On top of the Aqua, there is a Windex, and a tiny Windex Light. If you are using a flashlight at night or guessing in the dark, get one of these lights. They are so perfect.
J
joe phibbs
yep: try two 90's
Why not try two thru-plate connectors: one on the bottom that you can screw a PL259(from transmitter) onto and another at the top? Use females mounted to the mast with solder ready connector) readiy available at radio store, solder the wires to each end and mount with plenty of sealer and you have a permanent in-mast RG8 arrangement. Think how easy it will be to check swr at base of pole and at top...and how easy it will be to disconnect your antenna from mast. The mast will be another ground site as well, which means better coverage.
Why not try two thru-plate connectors: one on the bottom that you can screw a PL259(from transmitter) onto and another at the top? Use females mounted to the mast with solder ready connector) readiy available at radio store, solder the wires to each end and mount with plenty of sealer and you have a permanent in-mast RG8 arrangement. Think how easy it will be to check swr at base of pole and at top...and how easy it will be to disconnect your antenna from mast. The mast will be another ground site as well, which means better coverage.
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