Is there a device that remotely sends its pointing direction? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: September 11, 2020, 10:02:41 pm
content: I am looking for a small device to sit on a rotating antenna mast that can send the direction it's pointing in, in degrees relative to north (True or magnetic). The mast is circa 60 feet tall, an RF link would be ideal, wired much less so. Cost IS an issue. Does any such device exist or could be fairly easily built or modified? I would also need some sort of display about 40 feet at ground level, from the mast. Thanks. Maybe a transducer for model aircraft?

author: fordem
author_rank: Regular Contributor
timestamp: September 11, 2020, 10:10:45 pm
content: Doesn't the antenna rotator have a display?

author: ledtester
author_rank: Super Contributor
timestamp: September 11, 2020, 10:18:54 pm
content: Are you talking about an electronic magnetometer? There are such modules you can talk to via i2C. e..g:https://youtu.be/BMLcac_HWYI

author: Simon_RL
author_rank: Regular Contributor
timestamp: September 11, 2020, 10:39:08 pm
content: Quote from: Chris Wilson on September 11, 2020, 10:02:41 pmI don’t know anything about antenna, but is it possible that the metal from the antenna will interfere interfere with any magnetic pointing device? Maybe an encoder might be a better option?

author: tkamiya
author_rank: Super Contributor
timestamp: September 14, 2020, 02:20:40 am
content: If I read your question verbatim, you are talking about a Synchronous motor. You have one at your antenna, you have another on your desk, they will point to the same direction.Antenna rotators/rotors have a potentiometer inside with some reduction. Meter in you house read off the voltage and point to direction on the scale. There were some that used stepper motors or other types of schemes. At least one company made a mechanical device that advanced the knob indicator. They were known to go off sync with the actual direction.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 14, 2020, 05:47:57 am
content: The direction part of an anemometer.

author: helius
author_rank: Super Contributor
timestamp: September 14, 2020, 07:22:53 am
content: Quote from: tkamiya on September 14, 2020, 02:20:40 amI used one of those as a boy, it was made by "Channelmaster" and worked as you described.Another example of a "remote direction sender" is the Engine Order Telegraph or chadburn.https://en.wikipedia.org/wiki/Engine_order_telegraph

author: Chris Wilson
author_rank: Super Contributor
timestamp: September 14, 2020, 12:26:47 pm
content: Thanks for the replies. Most antenna rotators do indeed give an indication of compass direction at the controller, but you have to first know where the antenna is pointing to set up the display. Normally you set it to point to magnetic north with the rotator set to a zero position. But how do you set the antenna accurately due north when you are looking at it from perhaps over 100 feet below and have to climb or lower the tower to adjust it? Having a remote means of seeing where its pointing for an initial set up, and knowing its offset from the desired setting makes things faster, safer and more accurate. It also allows you to check if any safety clutch mechanism to allow strong wind gusts to move a big antenna rather than put huge torque loadings into the tower and rotator, have in fact moved it from its correct orientation. The latter was the situation that had me thinking along these lines as I couldn't understand why signals were weak until I realised the antenna's real position was no longer in agreement with the rotator controller's display.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 14, 2020, 03:39:36 pm
content: Every phone has a compass sensor these day's.They're usually hall sensors in 3 directions that measure relative strenght of the earth magnetic field, combined with a uC to interpret the data.But beware that the earth magnetic field is rapidly migrating the last few years.It may be the start of yet another North / South flip.

author: fordem
author_rank: Regular Contributor
timestamp: September 14, 2020, 04:16:32 pm
content: Quote from: Chris Wilson on September 14, 2020, 12:26:47 pmYes, there are times when the rotator and the display positions won't be in sync, however the rotator controller should have a "re-sync" procedure to deal with that - the only time you should have a need to worry about accuracy is when it's being installed.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: September 14, 2020, 05:59:46 pm
content: If you live near the coast, every navigation chart has the magnetic vs true north data on it. I dont know about inland bodies of water. You might be able to use a land survey too.Another idea would to try to use a local signal source that's in a known direction. There are phone apps for this. For example, you can try to use a local TV station. Get the app for aiming your digital antenna. When you get the strongest signal, check your offset.

author: drvtech
author_rank: Regular Contributor
timestamp: September 15, 2020, 10:14:20 pm
content: It sounds as though all you need is an index sensor so that you can resync the rotator control with a known antenna bearing. If you put a permanent magnet on the antenna itself (so that it is not affected by the clutch) and a Hall effect sensor on a bracket fixed to the mast, that would give you a repeatable index or 'home' bearing. You still have to calibrate it initially but that applies to any method.

author: Brumby
author_rank: Unknown
timestamp: September 16, 2020, 12:10:50 am
content: Quote from: JustMeHere on September 14, 2020, 05:59:46 pmThis is where my thinking went as well. ^ ^ ^Doesn't have to be a TV station, just any signal you can pick up that comes from a static location.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: September 22, 2020, 01:19:27 am
content: Quote from: Brumby on September 16, 2020, 12:10:50 amI suggested TV stations b/c there's a phone app that will give you exact bearing (well as good as a phone compass) to the tower.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: September 22, 2020, 11:15:16 pm
content: TheMA302gives anabsoluteangle reading relative to a magnet ring. It's like the best aspects of a Hall effect sensor and a compass rolled into one. It costs < $10, but there are of course other options.Personally I agree that a combination of rotary encoder plus a precise indexer such as a regular (intensity, not angle) Hall effect sensor is the better solution.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 23, 2020, 01:52:19 am
content: The solution to finding which direction the antenna is pointing without climbing the tower even once is a mirror. The simplest solution uses the simplest mirror, just a normal flat mirror. Place it horizontally on the ground, a chair or other surface at the base of the tower. Place a compass on the mirror. Then look down into the mirror to see the antenna reflection and line it up with the compass. A little thought will tell you where to place the mirror, compass and your head to avoid geometry errors.A more complex setup would use partially silvered mirrors to superimpose the image of the antenna on the compass image.