Revo-oplink Data+control unstable communication
« on: November 21, 2017, 03:01:36 pm »
Hi there:
Days ago I tried data+control in my revo and oplink just to reduce weight on my project.
I have used it only for data before and I never experienced a no signal situation even trying to have a no control signal situation to find out range (2.4 ghz and return home failsafe).
I have read about some testing from you guys talking about power setting, reflections, etc, and some other failures like this from other.
I need some clarification on this, some stable configuration in setup and hardware (antennas)

In My ground test I experience signal loss at very close range and at 40m did´n walk further away. I have the Oplink + BT on the tx, revo on the quadc.

thank´s

jdl

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Re: Revo-oplink Data+control unstable communication
« Reply #1 on: November 21, 2017, 04:40:27 pm »
Hi,

I believe the 433MHz OpLink can be used for a reliable Long Range Control & Data at the same time. I run it at 57600bps.

Best results so far with DIY half-wave dipole with ferrite bead on ground TX (relay box) and half-wave dipole on the fixed wing. I use coil-loaded dipole on the quad because of space limitation there.

Ground TX antenna benefits from being positioned as high as possible.

ZMR250 quad cannot reach the limits of 100mW Oplink control in the open air, due to the battery limits - some 5.5-6km max.

Fixed wing can go some good 10-12km away, maybe up to 15-20km in very clean RF conditions with 100mW.

With an upgraded to 1W ground Oplink (modem replaced with RFM23BPS), at least 50km should be achievable but this is TBD.

The ground relay box I made runs Oplink, two Bluetooth modules (telemetry to PC and to Antenna Tracker), 2.4GHz Radiolink receiver that also transmits at 2.4GHz, has also arduino for logging UAV data on MicroSD and driving OLED display. All this stuff + switched 5V voltage regulator (additionally LC filtered) is packed in a tiny box and runs without interfering with each other.

I've initially experienced rather limited Oplink range (1.2km max with 100mW TX power) with the fixed wing. Connection was failing with RSSI indicator showing only -62dB. The issue was tracked to be a VERY NOISY switched voltage regulator on the Eachine ET600R VTX. When the problem was sorted out (shielding and ferrite on the VTX power supply wires helped in this case) first noticeable packet loss starts at -80-82dB and link usually fails above -85-87dB.

I submit some photos of antennas & UAV configurations I've recently used. Also here is a snapshot of the GCS telemetry playback (RSSI) of a test flight with the wing to 11km distance forth and back.

Displayed RSSI is for the received signal coming from the aircraft, transmitted from the Oplink embedded in its Revo FC, 100mW TX power. -76-77dB when the distance is 11km. There are two noticeable worsening in the RSSI graph when flying over a RF noisy area (nearby settlement). Yet no significant packet loss at -85dB.

Re: Revo-oplink Data+control unstable communication
« Reply #2 on: November 21, 2017, 05:24:31 pm »
@jdl
Are you using Revolution in aircraft or FC+OpLink?  I am currently having problems with [email protected] in air, but not with [email protected] in air.

Also not having problems if I reduce [email protected] in air to [email protected] in air.

Verified with data only and with control+data.

Also, do you have links to buy your antennas?

jdl

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Re: Revo-oplink Data+control unstable communication
« Reply #3 on: November 21, 2017, 07:08:09 pm »
@TheOtherCliff,

I'm using Revolution with its embedded RFM22B module, on both aircrafts. Never tried FC+standalone OpLink combination.

All the time running [email protected] Data+Control, 57600bps. Never tested flight with lower power settings and lower bitrates.

I've built the antennas following the IBCrazy tutorials:

https://www.rcgroups.com/forums/showthread.php?1159968-Build-your-own-TX-antenna-for-FPV

Even better guide:



0.8-0.9mm MIG wire (stiff) for upper part, bicycle gearshift flexible strand for lower part - it bends safely when the plane is landing. RG316 coax cable. Used a big drop/blob of 5-minute epoxy to fix and strengthen the solder joints to the coax. No ferrite bead on wing antenna - could not find suitable one.

I've never planned buying or selling these simple half-wave dipoles as they are so cheap and so easy to build following the tutorial.

Btw, I checked your thread about problem @50mW but I cannot guess anything helpful :(

Yesterday parts arrived and I assembled a DIY RF power meter following the Mr.RC-CAM guide (Big Thanks! to him for the design and code):

https://www.rc-cam.com/forum/index.php?/topic/4139-diy-rf-power-vswr-meter-low-cost/

and used the meter to check Revo RFM22B output power at 1.25, 1.6, 50 and 100mW settings. All seems normal. The same is with standalone OpLink at these settings...

I've ordered and waiting for a cheap RF bridge to use with RF Power meter for antenna SWR measurements.

https://www.ebay.com/itm/RF-bridge-0-5-3000-MHz-VNA-Return-Loss-VSWR-SWR-reflection-bridge-antenna-/332052527822

I'm really curious to check my 433MHz dipoles with and without the ferrite bead. Also some DIY/(remanufactured from cheap Banggood ones) 1.2GHz Skew Planar / Cloverleafs against the excellent TrueRC Singularity.

Re: Revo-oplink Data+control unstable communication
« Reply #4 on: November 21, 2017, 09:32:11 pm »
jdl:
thanks very much for your answer. I will start filtering power supply in both sides. I haven´t do fpv yet, only have revo, pdb and esc on the quad.
On transmitter I fill an empty module case with oplink, 5v reg and HC-06.
I'll check the antenna building tutorial and build some antenna.
My settings are the same 57600 and 100mW.

jdl

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Re: Revo-oplink Data+control unstable communication
« Reply #5 on: November 22, 2017, 08:58:39 am »
@ppnvedado

You may first try replacing the switched 5V regulator/BEC on the quad with linear 5V reg, and disable this switched one on the PDB, if this is your case. This way you will know if the switched BEC is the culprit.



Re: Revo-oplink Data+control unstable communication
« Reply #6 on: November 22, 2017, 07:39:34 pm »
ok, thanks. I´ll do that.