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Terry

Auto Tracking Aerial

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Thanks for the link its interesting to see but as you say not much help directly. The main difference is we need to track a moving object thats signal will fluctuate in turns.

Terry

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Just another bump. Did crash test ever get his working? Any new information anyone would like to share? I found this guy who did some high altitude balloon work and also made a device similar to a TInyTrak that plans on incorporating antenna tracking into his next release. See slide # 22

http://n1vg.net/tracker2-dcc2006.pdf

-dave

Edited by dalbert02

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hi Terry!

i have already worked on this project using micro controller PIC 18F242. For this project you need stepper motor , GPS receiver and transmitter and receiver to transmitt and receive GPS Data.

To transmit GPS data you have to use the transmitter which is RF and communication is serial.

so you can use Max Stream "Xstream PKG-R 900MHz" transceiver for your project which is serial RF Modem and can transmit or receive data serially at 9600 baud rate.

but make sure that at the starting of the project you have to allign the antenna to True/Magnetic North direction.

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Hi Reuben,

I used an Airwave 508 at the time, it's a very old project now.

Terry

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Did you make some improvements on it? Or are you still using it? Were you happy with the results? I think you´ve posted you changed to a 4 way diversity receiver.

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Did you make some improvements on it?

Yes I did. The main changes were to the way the RSSI signals were processed to ensure the patch tuned the right way in the shortest time.

Were you happy with the results?

Yes and no. I was happy with the tracking at medium and long ranges and I used this system for over a year with no need for a helper to point the aerial. I was not so happy with the tracking at close range particulaly when the plane overflew the aerial as it would loose track for a few seconds. The other problem was the slip ring for the video signal and power add noise to the picture.

I think you´ve posted you changed to a 4 way diversity receiver.

Yes correct again. When I started the tracking aerial prices were high for 2.4Ghz parts but now they are low which makes a 4 way system affordable. The 4 way system is IMO the perfect system at all but the longest ranges. My first 4 way system is that I used to test the idea is for sale, it's very heavy and very untidy but it works well for anyone wanting to try a 4 way system. Please pm me for more details.

Terry

Edited by Terry

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Perhaps the "Perfect" rx system would be.

Autotracking aerial based on rssi for long distance and using a really high gain antenna (yagui, parabolic, or soo)

Autotracking aerial based on gps for medium and short distances, using some 8dbi patches.

Both autotracking receivers conected through Oracle Diversity receiver.

That would probably meet all our needs B) but would be complicated to mount all that stuff at the flying field, and too much electronics involved to trust them.

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Which receivers did you use for your 4-way diversity?

508's. had a good signal over 1.5 miles on 100mW with it.

Wavess, the other reason it is MY perfect system is it easy for me to carry, I often walk to my flying field with all my gear.

It's a no fuss switch on and forget system. I did always intend to do a high gain auto tracking system but I just have no need for it.

Terry

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I still play arround with Antenna tracking systems,

see my tiny development platform here:

http://www.webx.dk/rc/video-wireless/antenna-track.htm

sorry if I have allready posted it before :-)

this servo X/Y idea can be scaled up to any size later / if / when the software proves to work good,

another advantage with thix X/Y servo way, is you can mount the receiver directly to the moving antenna,

and no video and power wires will be rotated, even if you fly in big circles all the time,

the antenna moves arround like your own arm will do.

I think light sensor is a good idea to show how it could maybe work when indoor and developing the sw,

this system will be based on RSSI or Video quality as the one signal input,

goal is to make the antenna point as accurate as possible, with as little jitter as possible,

and to point right as fast as possible, all this is extreamly difficult I have realized when playing with this :-)

Edited by ThomasScherrer

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I still play arround with Antenna tracking systems,

see my tiny development platform here:

http://www.webx.dk/rc/video-wireless/antenna-track.htm

sorry if I have allready posted it before :-)

this servo X/Y idea can be scaled up to any size later / if / when the software proves to work good,

another advantage with thix X/Y servo way, is you can mount the receiver directly to the moving antenna,

and no video and power wires will be rotated, even if you fly in big circles all the time,

the antenna moves arround like your own arm will do.

I think light sensor is a good idea to show how it could maybe work when indoor and developing the sw,

this system will be based on RSSI or Video quality as the one signal input,

goal is to make the antenna point as accurate as possible, with as little jitter as possible,

and to point right as fast as possible, all this is extreamly difficult I have realized when playing with this :-)

And yes yes my friend, get a move on it man! :D

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Looks like no news from Thomas but I thought I would update my project.

As some will know I am using 5.8Ghz now due to the huge amount of flak from wifi so my latest auto tracking tests have been on here and not 2.4Ghz.

My first tests were for an RSSI driven pan and tilt system which gave mixed results. I used 3x 14dBi patches and 3x DPCAV receivers and a servo for tilt with a stepper motor for pan. For about 9 times out of 10 the system would track great and was fantastic for pointing at the plane to regain lost visual but at odd times it would point vertical for no known reason. I spent a lot of time trying to cure this but still just when I thought it was sorted it would do it again. While testing I noticed that for most of the flight the tilt angle was very low and it only went high at close range or when overflying myself so I decided to cut my losses and make a pan only system like I did before. This dose leave slightly less coverage but it makes the whole thing MUCH more simple and give more reliable long range operation.

I use over the last month or so it has only lost track while overflying myself which is to be expected and not a problem as I tend to fly out in one directon and only overfly myself when getting ready to land. At low level the signal is not lost even if poiting the wrong way at this hight. If the unit dose loose track for any reason I have a simple system to correct it. I just turn it by hand until the video is regained and let it carry on tracking as I have mounted it on a slipper clutch. Its a bit like in the old days when I used to turn my patch by hand as I flew out of the beam.

My longest flight yesterday was about 1.4 miles and all went well with no loss of track, I expect 2 miles to be possable but I was trying to teach someone to fly at the same time and I had no spotter so I turned early. The video is dead boring but it shows the range on the OSD.

http://www.vimeo.com/6529451

Terry

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Yep made a longer one today,over one and a half mile this time.

The patches Im using are made by itelite http://www.msdist.co.uk/product_58Ghz_IT_Elite_14dBi_Panel.php

edit; Just thought I would add that the patch is smaller than some 8dBi 2.4Ghz patches.

Terry

Edited by Terry

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Well due to some more interest in auto tracking without the use of GPS I thought I would add that I have been using this tracker for over a year now with no problems. It was used today and helped me see from which direction my plane was coming from after my video glasses went dead and I was forced to let the auto-pilot return it for me :)

The only time it ever loses track is if I over fly a 60* cone above it but the only time I do that is when Im under full visule ready to land so its a non event.

I have also added a slip ring for the video out now so flying round and round myself or pre take off when it would twist up the lead dose not happen.

If you want help with your own auto tracker I will try to help but I must say now THERE ARE NO PLANS OR CIRCUITS FOR THIS PROJECT. I have been asked many times for these but it is a project that has been modified many times and I have no idea of the exact circuit.

If your keen to have a go I would say collect the parts and build the hardware first, many guys start with the electronics then cant get the hardware to match.

It will track fine with 2 patches but as I had 3 from when it had vertical tracking so just kept it for a better signal.

Sorry about the bad pic but I hope it gives you the idea ;)

Terry

post-16-096819600 1289681890_thumb.jpg

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Very good, show your stuff. :)

How about a description of how it works. For example, does it use a continuous rotation servo and compare the RSSI from two sources and spin until they are about the same? Or, does it do some significant magic, perhaps in a micro, to compute the antennas required compass angle?

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Yep continuous rotation since the last month , as I said it no longer twists up the lead which was a real pain.

It uses a stepper on a 9:1 belt drive for pan and did use a servo for tilt but as I gave up on the tilt as too much trouble and not needed 99% of the time.

A PIC (yes you knew there had to be one) measures the RSSI from the 2 outer panels and moves the stepper to try and balance them. When the stepper PIC (yep another PIC) is told to move it will do so very slowly at first and ramps up to fast over about 2 seconds. This means it will not over shoot when only a small adjustment is required but will be fast enough to keep up if flying past the aerial at close range.

The 2 RSSI signals are also damped with a resistor and capacitor to smooth out any tiny glitches in the signal, this ensures a more solid response.

There are also chips checking if the signals are valid video and not interference which helps it not move the wrong way but it seems to work ok without them.

The patches as said before are 14dBi and the angle of the outer 2 is set so as the lobes dont give incorrect infomation to the PIC. What I mean by that is that most aerials have a main lobe of max signal and sometimes many side lobes. If the tracker is pointing say 20* left but the left patch is inbetween lobes but the right patch has a good signal from its side lobe then the tracker will move the wrong way. So in short the angle and patches used are very important if the tracker is to be reliable. Dont choose very high gain patches with lots of pointy side lobes unless you want to risk losing track. 14dBi has given over 3.5 miles with a 5.8Ghz 500mW TX so its no short of range.

I am working on another system with more range just for fun but when I will find the time to build it who knows ...

Terry

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Thanks Terry, as I was one of those that enquired about your 'rig'.

I have several bits of the hardware (including the same slip ring - oddly ;) )

As Terry indicated, get the hardware together first, then make the electronics work afterwards.

This is also an interesting KISS approach, not disimilar to yours

http://www.rcgroups.com/forums/showthread.php?t=1337608

I need a non OSD based tracker as the FY21AP I am installing into a Skywalker does not send back the GPS data (unless anyone knows different or how to interface the GPS data at the 'plane end and feed it down an audio channel (AFSK modem perhaps?)).

Anyway, I think the non GPS base is a good way to go.

Nigel.

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A different architecture I considered was to use a single patch antenna on a turntable. This "sensing" antenna would have a receiver module attached to it, with local battery power (no wires, no slip rings, fully self contained). The antenna would be spun at about 120 RPM. As it rotated it would know the compass direction based on a simple rotary encoder on the motor shaft.

The magic part is that the receiver module's RSSI would be monitored on-the-fly, as the antenna spun around. This would allow it to find the compass direction of the strongest RF source. Once the best RSSI direction was determined, it would send some positioning data over a low power RF link to a typical servo driven antenna tracker.

The advantage of this is that the sensing antenna's side lobes will not have any significant effect and you never have to move the main antenna if the RF signal is intermittent or experiences long fades. Plus, I like things that work differently than the mainstream methods. But, it's a project that just sits in the idea jar, at least for now. :)

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