DIY Antenna project with FrSky Telemetry

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kaos
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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Sun Feb 09, 2014 12:01 am

skyscraper wrote:Falcon looking good. landing gear should work well fro the maiden if you have a runway to launch from too!
that is the main reason I put those wheels on. with the mod I have done on it, God knows where the CG would be. ;)
To hand launch it 1st time, I might as well throw it into the ground. :lol:
The some form of inputs I currently have is to either plug a GPS direct to it ( you could also set it up to listen to a GPS attached to something else) or to read the Mavlink protocol data from an Ardupilot or PixHawk etc. The board has an eeprom on it so you can have various configs. There are 2 simultaneous outputs possible One is a serial port output (which with my initial software sends data to the FrSky telemetry receiver). The other output is an audio waveform which you can send down your Video audio channel.
those multiple inputs are really great, make it a lot more flexible.
as for the eeprom have different configs, do you mean you can 'select' which input source you want with a software switch without reflash the eeprom? If so that would be super. ;)

Another question is your mentioned the initial software sends data to Frsky Rx. I remember the Frsky rx only sends telemetry data every so many frames, this won't affect the tracker accuracy significantly right? Assuming I get my 100mph plane in the air with the tracker. :mrgreen:

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Mon Feb 10, 2014 7:35 am

Once you are more than 100m from you, accuracy is not an issue.

You only need to move a small amount to keep in the beam.

Its why most GPS trackers look like they lag when close by.

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Mon Feb 10, 2014 7:52 am

that makes sense. Just want to be sure. Newbie, you know. ;)
Just a hypothetical question: if I am using a tracker system doing FPV over 2Km, while flying back and near, say 10-20 m from me over the landing strip and I have a 100 mph plane doing a fly by to show off ;), I only use a narrow beam helical tracker. would that get my plane out of radio beam range if the tracker is lagging behind some what?

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Re: DIY Antenna project with FrSky Telemetry

Post by Kilrah » Mon Feb 10, 2014 10:10 am

The antenna's reception pattern is not "yes or no". You'll probably have 20dB less if you're in the worst reception zone of your antenna, but then you'll have 30dB more in your link budget simply because your TX is next to it and not 2km away. If your TX is within 10m of your RX you'll have a picture even without an antenna on the receiver...
But I would not use only a narrow beam antenna anyway, that would always be in a diversity setup with an omni.

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Mon Feb 10, 2014 7:13 pm

got it. thx.
yes, I saw the diversity thing in Rob's setup. That will be included in mine too. ;)


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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Tue Feb 11, 2014 7:44 am

kaos: regarding the airborne unit. Yes it has a "command line mode" so you can configure it by plugging it in to a serial port. There is an eeprom on the board to save your settings when you switch off. Maiden flight of your Falcon cant be far off now? :)

re the diversity (2 video receivers) I've dont use it at the moment. Ive flown a helical with a 25 mW transmitter (using my tracker) and I havent had a problem so far even with that low power Vtx. That said I do have a form of diversity since I have the Vrx on my goggles, though I would have to manually switch to it. I had thought about making a dish antenna. The plan would be to make the dish shape ( an offset style one ) on a 3D printer and cover it with foil, then I guess a diversity receiver would be needed.

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Tue Feb 11, 2014 7:46 am

You can would also need to watch your polarisation.

When the signal bounces off the dish, it would swap from right to left etc...

Rob

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Thu Feb 13, 2014 10:36 am

Rob Thomson wrote:You can would also need to watch your polarisation.

When the signal bounces off the dish, it would swap from right to left etc...

Rob

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Thats a very good point which I hadnt thought about! but Its no great problem. My helicals dont cost much...

zoomworks DIY helical antenna :)

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Thu Feb 13, 2014 7:45 pm

thx for the detailed helical construction. I was just about to search for that info. I like that template for 7 turn helical. Will start collecting junk tin can to make it. :mrgreen:

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Sat Feb 15, 2014 7:20 pm

Not really open source...

But I think you may like to see this :)

https://www.youtube.com/watch?v=cPo3f8n ... ata_player

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Sat Feb 15, 2014 8:23 pm

Rob, your are one goggle short. :P
In that suit case, is there a wireless relay for radio Tx? or everything is for video only?

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Sat Feb 15, 2014 8:28 pm

Video only.

I have moved to UHF for control :)



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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Sat Feb 15, 2014 8:45 pm

I see. which UHF system you like/use?

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Sat Feb 15, 2014 8:47 pm

Rink by Royal way.

Plug and play :)



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Re: DIY Antenna project with FrSky Telemetry

Post by LeoLeo » Sun Feb 16, 2014 2:33 pm

Dear skyscraper,

I built a new copter based on multiwii last week - intended for flying fpv. Right now I only have a CL/SPW antenna setup. I'm thinking of building an antenna tracker on the cheap. While searching for a solution that could make use of my existing setup, I found your project.
Since I don't want to hook up some cable to my 9x transmitter I'm very interested in your upcoming solution to use the audio channel of the video-link. Secondly, I wanted to know if your system could make use of my already existing GPS sensor on the copter (hooked up to an i2c-gps-nav by eosbandi).

Regards,
Leo

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Wed Feb 19, 2014 9:46 pm

Hi LeoLeo,

As it stands the option to use the audi channel of the video link isnt complete yet. Ive done some pcbs, but not the software. I'm currently working on adding a magnetometer to the ground side and I hope once that is sorted, I can get straight on to finish the code for the airborne unit.

As to whether you GPS will work, currently the only one that will work is one with MTK3329 chipset using a serial port. Using I2C for GPS is an option I hadnt thought of, however there is an eeprom on the board that uses I2C so it would be feasible with a few changes.

Apologies to everyone that has expressed interest in the project. Its taking a while longer than I expected. However I'm making headway slowly!

Hope also to get some more documentation done at some stage!

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Wed Feb 19, 2014 10:17 pm

Take your time. I have not found the tin can yet. :mrgreen:

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Thu Feb 20, 2014 12:00 pm

kaos wrote:Take your time. I have not found the tin can yet. :mrgreen:
Thanks for that kaos :) Ah yes. You need to select your tin can carefully !

I am also currently looking at how to make connections to the discovery board more practical. So I'm going for a piece of double sided veroboard (the type with individual through holes rather than stripboard). The connectors for the discovery boar go one side. Then the current plan is to use a 34 way header connector the other side. with an IDC connector to the motor encoders etc, so you just unplug that to extract the discovery module for neatness. For V2 there is also the option to add a modem ic and an eeprom and connectors for the magnetometer and gps, but I hope also to make it so you can start with V1 and just upgrade to V2 as you like.

The airborne unit will work with V1 if you use the FrSky connection but you will need a modem IC added to the ground board for receiving data down the audio. (On the airborne side there is no need for modem as the audio wave fome is all generated by the stm32 Digital to analaog convereter) For the ground board modem IC I went for a TCM3105 since they are cheapest and most easily available on ebay. e.g tcm3105 on ebay. They arent the simplest though so if you are adventurous you could opt for the MX614/FX614 which is harder to get and pricier but needs less surrounding circuitry, but is otherwise pretty much compatible.

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by LeoLeo » Thu Feb 20, 2014 4:10 pm

Hello skyscraper,

Does your code parse the standard NMEA messages? If so, I think it would be possible to tap the serial connection between the gps module and the i2c-gps-nav. At least in my setup the i2c-gps-nav is only parsing the serial NMEA messages that are coming from the gps.

Regards,
Leo

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Thu Feb 20, 2014 5:13 pm

LeoLeo wrote:Hello skyscraper,

Does your code parse the standard NMEA messages? If so, I think it would be possible to tap the serial connection between the gps module and the i2c-gps-nav. At least in my setup the i2c-gps-nav is only parsing the serial NMEA messages that are coming from the gps.

Regards,
Leo
Hi Leo,

The unit does parse the NMEA messages. I have an old arduino version of the airborne unit which sends data down frsky only ... quantracker_air. ( The new V2 version uses an stm32f0 because I can create the audio using the DAC, but the GPS part is based on the code in quantracker_air just modded for stm32. The baud rate may need to be changed for a differnt gps

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by LeoLeo » Mon Feb 24, 2014 9:59 pm

Hi Andy,

thanks for the arduino code. Unfortunately your code is too sophisticated for my knowledge. I never used something else as the arduino IDE.
Maybe I find time to look into that a little deeper next weekend.

regards
Leo

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Tue Feb 25, 2014 11:18 am

Hi Leo,

Its true that the code isnt Arduino compatible. However if you want to persevere then you could try writing a raw C or C++ application (e.g Hello World) .

To compile and build the application you already have a C/C++ compiler.. Its the avr-gcc that Arduino uses (On my system the compiler is in ARDUINO_VERSION_TOP_DIR/hardware/tools/avr/bin/avr-gcc.).

In the directory where your source file ( e.g helloworld.cpp) is to invoke avr-gcc on it is simple..
$< ARDUINO_VERSION_TOP_DIR/hardware/tools/avr/bin/avr-gcc hello_world.cpp
Then look in the directory and see if you have 2 new files a.out and hello_world.o

If so it worked (Obviously it wont run on your PC though!)

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Thu Mar 06, 2014 11:48 am

Here is a picture of the extension board for the tracker on the ground. It plugs into the Discovery board and a IDC connector plugs in to that for most of the I/O. As you can see I am using my original Tracker for testing, so as to keep my V2 for flying. The board in the pic is double sided single hole veroboard, hence all the wires, but I will do a pcb to make it neater. The wires going up the stick are for the optional magnetometer and GPS. The extension board also has optional provision for an eeprom and the modem IC.
ground_extension_board.jpg
Extension board to attach to the STM32F4 Discovery, for the DIY antenna tracker ground side
regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Fri Mar 07, 2014 7:06 am

getting there. ;)

I was test making a helical antenna using a 0.8mm MIG wire (the only wire i have laying around) with your template to get a feel. found the MIG wire is too stiff and after winding through the template it ended up with a 2cm diameter helical. :P It won't stay centered around the plate.
140306.jpg
Is there any reason NOT to buy this one: http://www.ebay.com/itm/P4PM-5-8G-Left- ... 5d473f106e
The only thing I don't see on the pic is it does not seem to have the impedance matching thing. I think I can add the impedance matching plate onto it.
It would cost me more to buy the material to make one.
Last edited by kaos on Fri Mar 07, 2014 7:16 am, edited 1 time in total.

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Fri Mar 07, 2014 7:11 am

Personally... They do not look that good.

I would suggest you spent £20 ($30) and got bignose13 on Fpvhub to make you one.

His work rather well and are super quality.

Me... I use twin circular wireless 13dbi ones. The are beyond good!

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Re: DIY Antenna project with FrSky Telemetry

Post by kaos » Fri Mar 07, 2014 7:20 am

errrrh, what is a twin circular wireless ? a trade name? How do you have a circular while wireless? :P

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Fri Mar 07, 2014 7:25 am

http://www.circular-wireless.com/en/pro ... liaxial58/

But they are quite pricey :-)

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Fri Mar 07, 2014 10:30 am

kaos wrote:getting there. ;)

I was test making a helical antenna using a 0.8mm MIG wire (the only wire i have laying around) with your template to get a feel. found the MIG wire is too stiff and after winding through the template it ended up with a 2cm diameter helical. :P It won't stay centered around the plate.
140306.jpg
Oh dear that wasnt meant to happen :) I use brass or copper wire. I guess your MIG wire is steel so is too stiff and springy. In UK you can get reasonable copper wire out of mains "twin and earth" wiring cable, the sort used for wiring up houses. Even though copper is quite bendy, it is remarkably stiff once in the former. You might even get away with flexible copper wire. The former will hold it in shape. I dont know if the fact its multistrand would matter or not. Might even be better.
kaos wrote: Is there any reason NOT to buy this one: http://www.ebay.com/itm/P4PM-5-8G-Left- ... 5d473f106e
The only thing I don't see on the pic is it does not seem to have the impedance matching thing. I think I can add the impedance matching plate onto it.
It would cost me more to buy the material to make one.
As Rob says I guess you can be more sure it'll work if you buy one he recommends, but it'll cost a bit for the bignose one form uk postage maybe. I would have thought the one in the link would be fine if you add the impedance match, as long as its basically made ok... But dont quote me !

Did you manage to get your Falcon flying yet?

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by skyscraper » Fri Mar 07, 2014 10:36 am

Rob Thomson wrote:http://www.circular-wireless.com/en/pro ... liaxial58/

But they are quite pricey :-)

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I'd love to do a head to head against my tin can one to see how much better they are. They would have to be quite a bit better to sway me from my tin can ones! Would love to get around to doing a 3D printed one one day.. but probably way too far down the list to happen any time soon !

regards
Andy

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Re: DIY Antenna project with FrSky Telemetry

Post by Rob Thomson » Fri Mar 07, 2014 5:52 pm

I am sure at some point we will meet up!

I had a super session today. Went for a meander over the RHS wisley gardens.



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