Tuesday, October 24, 2017

Using a quadcopter to hang an antenna line

80m dipole up 90 feet. Ladder line allows use on 30 & 40.
For several years now I've used a quadcopter to hang my dipole and other wire antennas near the top of very tall trees and thought I would post a few photos of the equipment used.

My quadcopter is the DJI Phantom 3 - I've also used the Phantom and Phantom 2 in the same way as described here. Since the later model Phantoms (3 and 4) don't have a spare channel available, I needed to use a separate transmitter-receiver to operate the payload release servo that drops a weighted line over the target tree.

Here's what I used in addition to the Phantom:

Cheap R/C transmitter-receiver

Payload release device

Add a reel of 20lb monofilament fishing line and a 2-ounce weight and you're in business.

The idea, of course, is to fly over a tree and then release the weighted line. The best way to do this is to fly well above the tree and then drop the line. This way the weight doesn't have to overcome the resistance offered by the tree canopy - it can fall free for a distance, gathering momentum before encountering any branches it has to fall through.

The Phantom (and perhaps other quadcopters) are well-suited for this in that they stay where you put them when flown in GPS mode. In other words, it's possible to "park" the drone above and on the opposite side of the tree from where you ascended. Its GPS fix will hold it there in position, within a foot or two, despite wind gusts or breezes. This provides time to pick up the other transmitter and actuate the control that operates the servo.

The weight will then drop, bringing the fishing line down with it. I then use this line to haul up a nylon cord which in turn hauls up my final antenna rope, usually a 5/16" line from the Wireman. My trees are 110 feet tall. Once the dipole is attached and both ends are hauled up, the 80-meter dipole settles to around 90 to 100 feet. I feed it with 450-ohm ladder line and have worked 30 zones on 80 meters in three years of DXing and 305 total DXCC entities in 5 years of using the dipole on 10-80 meters before installing a tower/Yagi.

If you've got tall supports, a dipole is an excellent antenna - and a quadcopter is a fast and easy way to get the support lines quite high and with a good degree of accuracy.
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DJI Phantom 3A fitted with receiver, battery and payload release mechanism.


A piece of scrap corner molding zip-tied to quadcopter holds the "antenna-raising" parts

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7 comments:

  1. Very cool John. I've been waiting for this report! Nice job and it sure beats a sling shot.
    vy best, Jim W1PID

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  2. Very cool idea and it beat trying to launch a line up in a tree, way better control and fun flying time as well.
    73
    Mike

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  3. I've used slingshots and bows & arrows but this method is by far the most accurate. It i salso the most expensive and really only makes sense if you already have a quadcopter and are having fun using it for its intended purpose. Used Phantoms and other drones are not so expensive and would provide a more economical way of installing antennas.

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  4. Very nicely done John! I'm just starting the process of putting up a longer wire antenna for winter. I wish I had 110 foot trees! My tallest trees are 60-65 feet. I add a line in the center to overcome some of the sag so it looks like a droopy W when it's done.

    Great picture of the long lead of ladder line streaming down. How do you get the feedline into your house? Does it end up close enough to it?

    73,

    Tim
    KA9EAK

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    1. Hi Tim - The ends of the dipole are actually bent down each tree about 15-20 feet since the two trees I use are only about 100 feet apart. The feedline is almost vertical and comes down to a balun (link below) near the shack window. LMR-400 then goes from the other side of the balun and on into the shack via a feed-thru panel.

      http://palomar-engineers.com/antenna-products/baluns-and-ununs/1-8-30-mhz-balunsununs/11-toroid-baluns

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  5. We use a drone with one thickness of painters tape holding the fishing line. When the drone is in place jerk the fishing line which rips through the tape and the weight drops. For us it has to be painters tape. Other types of tape were to strong or not strong enough.

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    Replies
    1. Excellent idea and a much simpler option that never occurred to me.

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