[lanzi]

Hi LIBREators,

as mentioned in my post in the Flight Test Team thread I am running a Telemetry setup using 2 3DR Modems for Ground Station Telemetry.
It seams some of you are interested in the setup, so I am trying to give a bit of background info on how I got it working.

The story on why I had to find a solution to get the 915 Mhz 3DR modems to work is quite simple.

The control link I am using for my quad is an 433 EZ UHF link. I am also using EZ UHF on all my other builds, so switching over to OP link for control or telemetry was not an option for me. i tried setting up 433 OP Link for telemetry only, though that did not behave with 433 EZ UHF.
Bluetooth for telemetry was not an option either as the range is limited to a couple of meters. (nice for setting up the quad but not really good for a solit telemetry link.

I am not using the original 3DR modems but the hobby king clones
http://www.hobbyking.com/hobbyking/store/__55560__HKPilot_Transceiver_Telemetry_Radio_Set_V2_915Mhz_.html
they are good because they have both usb and 6 pos df 13 connectors.
the trick to get them working is to use the APM planner for setting them up. The wire to connect them to the revo or c3d can quickly be soldered up. it is pretty much the same as we use for the HC 06 bluetoot module. RX-TX/TX-RX/GND-GND/POWER-POWER. Baud rate is 57600 just like the bluetooth setup.

If you buy a set from hobby king, they come prebound. you need to hook them up with APM planner and rund the configurator on them. It is important to disable MAVLINK in the configurator. That is really important to get a reliable link between OP REVO and the 3DR hardware. once that is done, just hook one modem up to the flexy or main on the REVO and one to your GCS laptop (in my case OSX was plug and play since APM planner installed all the drivers).

The 3DR Modem will show up in OP GCS. Did a distance test with them using the 2 standard rubber ducky antennas. 2 km are no problem and i had the following frequencies running at the same time. (433 for control, 5.8 for video, 915 for telemetry). I hope that helps.

please feel free to ask any questions. will post a few photos later.

cheers
lanzi

[ArnhemAnt]

Thanks for sharing this lanzi.

I also fly 433 radio link on some of my frames and this setup sounds ideal. If you are getting out to 2klm with it then that is fantastic. Looks like I am about to shell out more cash for this hobby.....

When you get some time, a few pics of the setup would be handy. Also, not sure of your video skills, but a link to a video about the setup would be awesome.

[RC Madman]

Cool, I have some 3DR clones from RTFQ's that I have leftover from the APM board I had. I will have to see if mine will work?

The Air unit does not have a USB so I will have to find out what I need to program it?

[RC Madman]

I was unable to get this to work. Ended up loosing radio bind in the process?

[jerzkoh]

I was thinking of the same config for LR flight!

TBS Crossfire at 868Mhz, 433 for oplink and 5.8 for video

I have not started purchasing anything yet 

[f5soh]

Using Oplink at 433Mhz should be a bad idea because his second harmonic saturate the Crossfire at 868Mhz.

Oplink can do Rc control + telemetry at same time.

[TheOtherCliff]

I bought a pair of 3DR telemetry on 433 from eBay for $20 shipped.
One had USB and the other had serial.
Wired them up as expected.
Used 3DRRadio.exe (runs fine with Mono under Linux)
Set MavLink to RawData
Made some other obvious setups like baud rate, Network ID ...
Let it update the firmware (even updates the RF remote across the RF link!)

It works, for telemetry, but the turn around time is slow.  If you watch it do the initial load of UAVOs you can see it is much slower than OpLinks, but that is understandable since it doesn't know where a packet ends and must time out to know when to send the packet.  A little work on the source code and it could recognize LP packets and work at same speed as OpLink.  I have heard that the 433 version can even be made to talk to OpLinks.

[lanzi]

i am still very happy with teh 915 3dr radio clones i mentioned above. as theothercliff mentioned the initial load time is a bit slow. but teh connection is reliable. especially under LP GCS. OP GCS dropped connection every now and then

[jerzkoh]

Using Oplink at 433Mhz should be a bad idea because his second harmonic saturate the Crossfire at 868Mhz.

Oplink can do Rc control + telemetry at same time.

Dang!

Pardon me noob question. Can I fly LR with the choice of RTB function without the OPlink but use OSD to overlay on my FPV screen? (FPV on 5.8G and Telemetry on 868mhz)

[TheOtherCliff]

If by LR you mean a Long Range System (RC long range radio), then be aware that LRS's are usually on 433 also and 433x2 is way too close to 868.  Another one to watch out for is 433x3 being close to 1280 (an FPV video frequency).

Otherwise (no 433 on anything) it sounds OK from what I read of your setup.

[jerzkoh]

Apologies to Lanzi for deviating/hijacking your thread!

TheOtherCliff ... There will be no 433 on my setup at this moment, many thanks for the heads up and information!