Ideas about antenna rotation system with feedback to a PC

[Alek]

Hi all. I just got my amateur radio license 1 week ago and now I wan't (or try) to build a rotation system on which I can put my Yagi for 2m band and use it to point the antenna to different repeaters.

For the control I'm planing to use 2 relays to control the polarity of the current to a DC motor that will drive the rig

What I want to do next is to build some kind of a feedback system which I will input to a GUI program so I can see in which direction is the antenna pointed at that moment. I'm thinking of getting the input in the 0x379 (Parallel port status input) and integrating it to the program.

I have a couple of ides of accomplishing this,

#1. Use a simple mouse scroll wheel that I will attach to the rotor of the motor directly or using some kind of a gear system so I can have a more precise reading.

#2. Using a potentiometer attached to the rotor, again directly or with a set of gears and somehow (Probably A/D converter) get a digital signal from it.

The most important thing (I think) is to get a countable input, so I can count it in the program and based on the number of impulses to get the direction thingy in the program moving =)

If anyone has any other ideas please let them out I'm open to suggestions cos at the end I want to have a 100% functional system and not be forced to climb on the roof every few days to reposition the whole thing

Thanks in advance,
Aleks

 

[Papabravo]

When you get all done remember to orient your yagi in the vertical plane. Most repeaters have omni-directional vertical antennas. If your yagi is mounted in the traditional "horizontal" plane your loss will be in the neighborhood of 20 dB or so. Also be careful about mounting it to a metalic mast in the vertical plane. You may want to invest in an antenna analyzer.

 

[BrownOut]

I like the idea of a direct reading device, such as a precision variable resistor. Counting devices as optical encoders can suffer from flash triggering, especially if you are using relays. What type of motor do you plan to use? If DC, then you probably want to use a transistor H-bridge to drive it.

 

[Boncuk]

For antenna direction feedback use the Gilham code.

 

[Alek]

Papabravo, I know that. I already have it set up to point to one repeater, but its a hell of a job climbing every time to change the direction of the antenna so I can work on another.

BrownOut, How can I then input the data from the resistor to the program that I'm going to make ? And yeah, it will be a DC motor, I will read up on H-bridges ASAP.

Boncuk, I searched up for Gillhan Code but I didn't find any good references nor a good explanation for it. Care to explain a little more about it and how can it help me in this matter ?

 

[Boncuk]

Hi Alek,

the Gilham code is used in aviation to transmit flight altitude with the transponder signal. Aircraft transmit at 12bit resolution for an accuracy of 100ft of altitude.

Attached is the picture of a 4 bit Gilham coded (also called Gray Code) disk and the function is explained in the word document.

Boncuk

 

[BrownOut]

BrownOut, How can I then input the data from the resistor to the program that I'm going to make ? And yeah, it will be a DC motor, I will read up on H-bridges ASAP.

It'll need to be converted to digital. It's an extra step. Counters can be an OK solution, but they can give errors. If you use them, you should have a way to reset your count while your antenna is the the "home" position". The Gray, or Gilham encoder is a good method too.

 

[Alek]

Thanks for the ideas guys.

I'll probably go with the Gillham encoder 'cos its the simplest and I think will gve the best result and it will be a hell of a lot easier to make the program when I will have a constant input versus a countable signal.

 

[BrownOut]

That encoder also provides good accuracy at the edges of the "counts"

 

[Alek]

In any way, I don't really need an accuracy to the milimeter

 

[PatM]

You don't mention what kind of a rig you are using.
I know some rigs have HF, VHF and UHF capability and do cover the 2 meter band.

If you are using a base station that has CAT support, there is a free program called HRD (Ham Radio Deluxe) that has support for rotor control.
Here are the supported radios:
https://www.ham-radio-deluxe.com/Home/SupportedRadios/tabid/98/Default.aspx
You can control a rig from your PC with a click of the mouse.
Ham Radio Deluxe > HRD v5
Also has support for tracking satellites.

If you are using a HT then this would not be a benefit to you.

 

[Alek]

Yes I'm using a HT but I don't see how that is relevant. HAM Radio Deluxe afaik, has an interface to specific rotor controllers and as you can see from the first post I want to build this one custom and unique.

 

[Boncuk]

Hi Alek,

if you want to use a pot check out Beckman Instruments. They offer mechanically unlimited pots with an electric angle of 355degrees.

Those pots are highly precise, fitted with ball bearings and have a starting torque of 2g.

Buying off the shelf they are pretty expensive, but they do offer free samples which are out of tolerance (linearity and resistance).

Boncuk

 

[BrownOut]

It also dawned on me that if you haven't picked a processor yet, you can cheaply get one with an onboard A/D converter, to convert your pot for display.