> Nope, because like you said, they would draw the feedline into the > strut, smashing it all up...
I regularly use cushioned clamps for attaching rigid feedline to unistrut. I usually buy them from McMaster-Carr, but I'm sure they're available elsewhere. McMaster-Carr has them available in "tubing sizes" in additional to normal trade sizes- 1 5/8" or 3 1/8" rigid line is really 1 5/8" or 3 1/8" OD. The soft plastic insert prevents the clamps from damaging the line. Here's what they look like: www.mcmastercarr.com - search for 32625T62 However, I wouldn't use them nor "mini's (Minearallac-type EMT clamps) on a tower, nor would I use any kind of off-the-shelf galvanized, anodized, any kind of plated unistrut on a tower. The galv on regular electrical-grade hardware doesn't hold up as long as most other tower-grade galvanized structural steel. Valmont makes good hot-dipped galv strut if you wanted to go that route. And as always, use only high-grade galv or stainless bolts, nuts, and other hardware to attach to the tower. Never ever use any kind of plated steel components on a tower. They will quickly rust and become semiconductors, and you will almost as quickly be banished from the site (assuming managed by diligent/competent people). Personally, I'd stick with the real stuff - stainless round member adapters (hose clamps) or stainless angle member adapters (beam clamps), and stainless butterflies or snap-ins. Do it once, do it right. If you make a few calls to local tower companies, I'd bet you'll find someone that either has a surplus that they'll see you at a fraction of the new cost, or maybe even a few 5-gallon buckets of hardware taken down that might still be in good condition and can be reused. As far as spacing between brackets/hangers, it varies with wind speed, icing conditions, and line size. Here's Andrew's chart, based on EIA-222: http://www.andrew.com/search/BN_96221.aspx Most towers around here come from the factory with brackets spaced at 4'. And remember, coax "hangers" really aren't hangers. They aren't meant to hold the vertical weight of the line - that's what hoisting grips (aka Kellems grips) are for. The job of the hangers is to keep the line from flopping around horizontally in the wind, not to hold the weight up. A properly-installed butterfly is only tight enough to keep the line from moving, not hold the weight. As an alternative to butterflies or snap-ins, on big towers where feedline "bundling" is a necessity due to congestion and to reduce the windload, the traditional techinque is to install runs of rigid conduit the entire length of the tower (inside preferably), and then using tie wires (12AWG THHN solid) or "band it" stainless straps to aggregate the lines together around the conduit, again at regular (4' nominally) intervals. Hoisting grips are still used every 200' to hold the weight of each cable individually. Tie-wiring a cable directly to a leg is generally considered bad practice for a number of reasons. First, what do you do when you come to a leg flange? If you hug the cable tight against the flange, the sharp edges of the flange creates a spot for it to wear through. If you form the cable loosly around the flange, it leaves it open for room to move and create new problems that way. Also, by being mounted to the leg, it becomes an obstacle when someone else comes along and wants to attach an antenna mount to the leg. It's also more likely to get damaged by climbers and rigging lines. The list goes on and on... Hope this helps. --- Jeff
