Auto Tracking Aerial

[Terry 5]

Funny you should say that!

The high gain system I am working on is much as you discribe but not 120rpm, I like to filter the RSSI so 30rpm would be my limit.

What is it thay say about great minds

Terry

[Devonian 0]

Another (daft) idea for the pot.

Transmit an individual tone/code over an audio channel, compared and combined with RSSI would prevent the GS from locking onto an unwanted signal on the same frequency as the VTx and prevent unwanted false tracking.

Nigel.

[Mr.RC-Cam 127]

The high gain system I am working on is much as you describe ...

Can't wait to see it in action!

... Transmit an individual tone/code over an audio channel, compared and combined with RSSI would prevent the GS from locking onto an unwanted signal on the same frequency as the VTx and prevent unwanted false tracking.

The problem with the audio channel is that the sub-carrier is about -20dB lower than the video carrier and it usually fails before the video is lost. So it is not a reliable signal to use in fringe situations. I think that just monitoring for valid video syncs (to confirm you have the correct signal source) would do the trick instead.

[Terry 5]

Nigel, I thought the same thing a while back but after more thought I decided that "wrong signals" were very rare. The only common wrong signal is your own reflected signal but this too would have the tone pressent.

I see no real reason to give it a try though as long as your software allows the system to fall back on to "non tone working" if no tone it availible.

Its worth going back and reading page one of this thread 2003

Terry

[tommyd 0]

hi all

i am looking for some advice for my antenna tracker project its an old ibcrazy schematic which was first discussed here in 2003 i am having problems with some rf noise from the slip ring which is a

Mini Capsule Slip Ring 6 Wires 2A 12.5mm 300Rpm A Type CCTV Monitor

can anyone recommend a better one

below a link to its first prototype test

http://www.youtube.com/watch?v=GVfJWILT7do

any help or advice appreciated

Tommy

[Mr.RC-Cam 127]

Detailed information about your project will be needed so someone can offer advice.

[Terry 5]

Hi Tommy, what signals are you passing though the slip ring?

I myself only pass video and use 3 contacts to do that to cut down the chance of noise from the contacts.

Terry

[tommyd 0]

Hi Terry / RC-Cam,

yes i am passing video +earth and 12v power + earth through the slip ring the pcb is on the rotating part so power has to go through the ring as far as i can see attached are a few pictures this is based on alex (ibcrazys schematic from 2010 which you where part of. Alex is fully aware of the project and has ok ed me to produce them

so i have attached a few pictures to look at

terry i have sent you a message if you would like to test 1 of the 2 prototypes i have to give me some feedback

Edited September 10, 2013 by tommyd

[Terry 5]

PM sent Tommy.

The only thing I would say is running 2 separate earth's would be my choice, one for the video and one for the power. I use an on board battery so dont have the same issue.

Just to add I mounted my modules directly on the back of 14dBi patches to keep loses to a minimum. What sort of range are you getting so far?

Terry

Edited September 10, 2013 by Terry

[Mr.RC-Cam 127]

I agree with Terry:

(1) Use on-board battery power and combine the available slip ring contacts for video and ground.

(2) Coax is very lossy on 5.8GHz, especially RG316. If you must use coax then I suggest lower loss semi-rigid (such as RG402) and reduce the lengths to a minimum.

More comments:

(3) The rotation servo should avoid sharing the same 5V regulator that powers your tracking circuitry. Dedicate another Vreg for the servo and for extra power supply noise protection add a LC filter on the V+ power input of the circuit board.

(4) On your next PCB revision move the SkyRF modules closer to the SMA connectors and eliminate the short strip line trace that connects them together.

[tommyd 0]

Terry / RC Cam

Thank you for your advice/suggestions

I will mount the battery in between the PCB and the top plate housing the antennas so it does not pass through slip ring

will place a lc filter on the board for the video and a separate v reg for the servo

move the SMA connectors to the modules and use rg402 for the coax as suggested

looks like revision 2 is on its way

Terry i have only tested at 500 meters with my tbs disco testing the tracking side only (uk weather is cack) but inhouse i can see the rf noise when the tracker is twitching when getting a lock this would suggest it would be very problematic at further range so all the above makes very good sense and i appreciate the advice from yourselves in getting this right

I will update as soon as i can

Thanks again

Tommy

[Terry 5]

Ive been thinking about this today.

1. Have you considered just using 2 aerials? My original design only use 3 as it had tilt as well as pan then when I gave up on tilt I kept 3 as thats what I had. During the pan & tilt tests I never had a problem with pan just using 2 aerials, I also added a bit of bias in the software so that the aerial that was used for video was pointed more directly at the signal.

2. Is there any reason you dont want to mount the receivers directly to the back of the aerials? I think it is worth doing.

3. I dont think your design uses a micro-controller but there are advantages of using one. eg better speed control, when to hold position and when to search for a lost signal are just the basics.

4. Dose your design detect valid video or just rssi?

Terry

[tommyd 0]

Hi Terry,

1 i have not thought of only using 2 antennas think it was mentioned on the other forum but i think the answer was the RSSI signal is very fickle and needed some time to get the reading, i can send you the data sheets of the design it will make more sense

2 The bi-quads are very small 50 x 75mm it could be done but i wanted everything on 1 PCB for people who want a diy kit version for self builds that way you could attach any antenna designs to it, but i understand it would be far better to mount them directly to the antennas to re-Duse the losses

3 I have just received a funduino r3 board in case its needed to settle the tracking but i have never used this software before so i have a lot of research to do but i can see others are using it on this design to convert the anlog signal to digital for better smoother running and the other basics you explained, looks very interesting can you point me to any good info on these

4 The left and right only receive RSSI and the center antenna gets the video signal

Thanks again

Tommy

[Terry 5]

Hi Tommy,

1. I used much less angle between the aerials so very little signal is wasted and with a little bias built into the software the aerial used for the video was never more than 10deg off which probably amounts to less loss than you are getting in your coax.

2. I understand you want to keep it simple but my receiver board is only 25mm x 50mm.

3. I know nothing of that board, I use a PIC 16F818 and a stepper motor.

4. Yes mine is the same plus the video is detected on all 3 receivers so the program can decide not only what the signal level is with the rssi but when the video is lost.

It may be that my system is over complex but I have never tried to do it any simpler, maybe we could get together for some side by side test? where in the UK are you?

Terry

Edited September 11, 2013 by Terry

[tommyd 0]

Hi Terry,

im in skelmersdale lancashire will be good to do some side by side tests and see your tracker in action it sounds the dogs nuts when you have time just let me know i can pop down and see you

tommy

[Terry 5]

That will be quite a long pop! about 3.5 hours I would think.

Just give me a shout when your available and the weather looks like it will play ball, Sunday mornings are my favourite time for testing as the wind tends to be kind. I open to suggestions though

Terry