Need thoughts on best method to move VHF antenna

Hi, so I’m trying to find a way to move a VHF antenna that will be attached to a mount. The main idea is that something will move the end of the antenna up and down and the Arduino will then relay to a Raspberry Pi the angle in which the antenna is aimed. We are also hoping to have two modes of operation. The first required being a fixed angle orientation where we tell the Arduino what angle we would like the antenna aimed then the antenna moves there. The second mode, but not required, would be a scanning mode where the antenna would continually sweep up and down and update the Raspberry Pi. This last mode doesn’t necessarily need to be a smooth sweep and could instead just be steps. The angles the antenna would need to reach are from 0 degrees to a minimum of 60 degrees below the horizontal axis, but ideally 90 degrees.

Our two main limitations are that the weight has to be as low as possible (<5lbs) and low power consumption. I know these are very general limitations but this is only one small part of a much larger system that isn’t fully developed so we don’t have firm values in place yet and instead just these general guidelines.

I’ve worked with Arduinos before, usually just for data logging purposes, but never to make something move so this is new territory to me. I was initially looking at using a stepper motor but was told there could be issues with slippage and then the accuracy of the angle of the antenna would be gone. Next I looked at using a DC brushless motor with an ESC that lowers the antenna with a cable over a pulley, however given that we are looking for more torque and less rpm’s I feel like this wouldn’t be a good application. Now I’m considering a lead/ball screw to move the antenna.

Given my extreme lack of experience I thought I’d ask you all what you thought. Am I going in the right direction or am I missing something obvious?

Thank you!

What is the beam width of your VHF antenna? Is it a Yagi? What frequency?

A "VHF aerial" could be the size of a desk or the size of a room. So what frequency, and what type.

Aerials are normally aimed with aerial rotators (single or double axis). They have worm drives, so they don't move under wind load. The come with a supply and control box. Leo..

TV antennas used to do this, before everybody got cable. You might find an old system? Or a new one if they still make them.

Wawa: A "VHF aerial" could be the size of a desk or the size of a room.

Or a Slim Jim or a J-pole, which don't need moving

kenwood120s: Or a Slim Jim or a J-pole, which don't need moving

Unless you want to receive someting from directly above.

A birdcage antenna (for weather satellites) has a dome pattern. Leo..

https://www.channelmaster.com/TV_Antenna_Rotator_p/cm-9521a.htm

Places still produce new ones. And at the price point of some of the new models, I doubt you would be saving money trying to build one from scratch.

aarg:
What is the beam width of your VHF antenna? Is it a Yagi? What frequency?

It is a Telonics RA-23k handheld “H” antenna, not a Yagi. (http://www.telonics.com/products/vhfAntennas/RA-23K.php). I’m not part of the tracking team so I’m not positive on the specifics of the antenna. This is the antenna their team typically uses for handheld tracking so they would prefer to use this antenna though that also isn’t set in stone if we find an antenna that is more easily implemented with our final design.

ddbranges: It is a Telonics RA-23k handheld "H" antenna,

That detail should have been in your OP. I think several of us were thinking you were talking about a roof/pole mounted antenna like those used for TV reception.

So if it's a hand-held antenna, just move your hand...

Duh

Allan

These 2-element Yagis are used horizontally polarised, because of the very wide vertical opening angle.

"...from 0 degrees to a minimum of 60 degrees below the horizontal axis..." From that I understand you want to move it vertically? (= useless). Leo..

ddbranges: Hi, so I'm trying to find a way to move a VHF antenna that will be attached to a mount. The main idea is that something will move the end of the antenna up and down and the Arduino will then relay to a Raspberry Pi the angle in which the antenna is aimed.

Thank you!

Hi, so you are building an Aerial/Beam Elevation device. If your speed of operation is not fast you can use a highly geared DC motor, say 5RPM output, the shaft twisting making the aerial scan up and down. Fit some limit switches for max and min travel. Position feed back can be an encoder on the shaft. If the installation is not going to be mobile the instead of encoder you could mount an accelerometer on the aerial and use gravity to reference your elevation angle. The amount of torque required to lift the aerial will depend on where you mount the pivot point on the aerial boom. Tom... :)

What kind of power do you have available for this project?

Paul