Dipole Sag due to feedline weight?

[AF6LJ]

Thanks, Sue. Exploring my property after moving in last year, I discovered a 20 pound piece from a Volvo engine in the woods. Now I know what to do with it instead of tossing it across the property line into the neighboring woods.

I prefer to use a couple of springs as apposed to counterweights.

[K8JD]

Weigh it before you hang it.

Hang it and if it breaks, put up bigger wire.

[KB0YYO]

I have a dipole up and I have it tied at both ends. With a counter weight on one end only so far. It is a gallon jug with about 6 inches of water in it for a weight and it works. The wore is straight so I think it is good enough. We have had some very strong winds and it moved about 6 feet up and down. So far so good.

[KC8QVO]

Hmm. If you really want to calculate the weight you need wouldn't it be the same equation as used for vectors/angular loads? Factor in the tension of the strung dipole (minus the feedline). Then calculate the vector force on the dipole due to the added weight of the feedline (weight/ft*height above ground or the closest fixed point).

With pulleys attached to your supports the vector force (simply here, negating friction and loss in the pulley and the weight of the support lines) from the feedline hanging + the tension in the dipole / 2 = the lifting force on each of the support lines.

This would be just to balance the system. Factor in a tad bit more weight to keep the system returning back to its original state, maybe 10-20% per side.

Now if I could throw in the equations for all this.. my brain is too tired though.

[WA7PRC]

I have a dipole up and I have it tied at both ends. With a counter weight on one end only so far. It is a gallon jug with about 6 inches of water in it for a weight and it works. The wore is straight so I think it is good enough. We have had some very strong winds and it moved about 6 feet up and down. So far so good.

I like that better than using a spring because a spring will eventually break or stretch. I'm not fond of plastic milk jugs because UV light causes them to disintegrate. Unless you're in the deep South, water tends to freeze, crack the jug, and leak out when it thaws. Heavy gauge plastic and dirt/rocks works. I tried that to support the apex of my 80m cage inverted vee + 40m dipole (a LOT of weight). A piece of plywood cut to fit the bottom of a 5 gallon pail prevented the bottom of the pail from blowing through. But, the wire handle was under a lot of stress. I went with a dumbell set + 10# weights:



I drilled & tapped one end of the bar and installed a 1/4" eye hook. The rope is 1/4" double-braided nylon and the end is attached to a bottom tree branch. A 3" diameter nylon + stainless pulley resides near the top of the tree. This setup has lasted (so far) several years with zero problems.

[W4PG]

I've put up dipoles for 40 years and simply hang them over a tree limb with nylon rope and tie the rope to a nail I hammer into the tree. While I understand the tree might not like getting hammered, I've never worried about "weights" or springs or anything, and the antennas have worked just fine.

A dipole is a simple antenna. I prefer not to make it complicated.

............Bob

[KF5FEI]

Brake rotors work pretty well too. And the odds of them rusting out are pretty slim. Should be able to pick several up for free at a local auto repair shop.

[W5DXP]

It is a gallon jug with about 6 inches of water in it for a weight and it works.

I did the same thing and it worked well until the first hard freeze.

[G0GQK]

The ARRL book states its XCx3 =y - g2 : 25 lbs