DSMX/DSM2- zero range [SOLVED!!!]

Edited 4/14. At this point I no longer feel as tho the receiver is my issue as I've replaced the in-question lemonRX (which never bound in DSMX) with a orange R615X and it functions EXACTLY the same (besides the fact that it does allow binding in DSMX mode). I'm pretty sure all that's left is the factory devo module in my 7E. If you're also experiencing this issue please feel free to post any and all info you find while we try to pinpoint this.



Hey guys, couple weeks ago I posted this thread about this 6Ch Lemon Rx I had just bought. Note this is the first and only DSM2/DSMX equipment I have so I cant test it with other parts.
It was marked (both on the retail packaging and on the little plastic board protector) "DSMX' but with DSMX selected as the protocol in the mixer it wouldnt complete binding. At mikemacwillie's suggestion I switched the tx to DSM2 and it bound within a couple seconds and does work. Problem is I'm only getting literally a few foot range. I moved the Rx outside of the 3D printed body thinking the PLA was somehow disrupting the signal but that didnt improve it any. I've went as far as replacing the Rx's antenna's (trimmed to the EXACT same length as stock) and adding an external antenna to the factory module of my 7E but that didnt improve things any.

I have done the range mod so I'm able to select output power and it is the same at every level so I dont think I'm overloading it.
Edit: to specify I get around 8' (~2M) range before it cuts out, it then will not link back up till I walk within 1-2'. Also I have the range mod done in a way I cant reverse it (i.e. the "diode" [which BTW is really just a 10k resistor] totally removed and pads solder bridged) and am running the 3/5 nightly. I have a real antenna for each of my 3 modules and to further troubleshoot I have unscrewed the 2 other SLA antennas (from the A7105 and NRF modules) to make sure that wasn't the issue.

I could really use any ideas you guys can give me. If that's buying an orange Rx that's fine too as I'm very suspicious this lemon was in-fact a lemon from the get go, the never binding in DSMX thing really bothered me, even tho it came from a trusted dealer (BuddyRC, which also happens to be my LHS). What can I do to pinpoint the source of the low range without ANY other spektrum based stuff?

Ok I've done some more testing hanging the model from my fan and testing range. On 100uW I get about 3-4", on 300uW I get about 6", 1mW = 14-18", 3mW = 24", 10mW = 3', 30mW = 4-5', 100mW = 7-8' and 150mW = about 8-9'. Please see youtube video posted a few posts down!

I'm starting to think it may be tx related. I notice the lemon drops signal when I simply move my hands around the transmitter but as long as I'm leaving the tx sit still I can block the RX any way I wish and it still maintains signal.

Cereal_Killer wrote: . What can I do to pinpoint the source of the low range without ANY other spektrum based stuff?

Do you have ANY other CYRF6936 based RX?
e.g. some Devo RX, so we can exclude a hardware problem in your TX.

linux-user wrote:

Cereal_Killer wrote: . What can I do to pinpoint the source of the low range without ANY other spektrum based stuff?

Do you have ANY other CYRF6936 based RX?
e.g. some Devo RX, so we can exclude a hardware problem in your TX.

Unfortunately no, however within the next few days I'm meeting up with a local buddy who does so I can do a range test of my tx with his stuff.

I'm starting to wonder the current demands of the RX, does anyone know? I'm feeding it 5v off the arduino's on board regulator which also poweres the two i2c devices (GYRO and 128x64 OLED), when I get to it today I'm going to switch to an unused BEC output so it can have up to 1A if that's the issue...


Edit I have switched it to being powered directly from a 1A BEC, it's the only thing on that BEC so plenty of power. Still the same.

and am running the 3/5 nightly

3/5???
What nightly build version is that exactly?


1mW = 14-18"
Is that 14-18 inches? 0,46meter???

100mW = 7-8'
Is that 7-8 feet? 2,1-2,4 meter???

I tested successfully a range with Spektrum AR6210 at 1mw of ~60-65 meters: www.deviationtx.com/forum/3-feedback-que...ions?start=120#31014

Without checking FlightLog fades, FrameLosses and Holds you can not really tell what is going on...

You get Holds after 3 meter???
Have you made any error on soldering??

Even on 7-10mw @Devo7E range limitation the full range should be much more?!?

I would suggest to get a AR6210, AR610 (not sure if it has 2 counting RX or 1 RX like AR600) + TM1000 and re-test.
You must at least have 30-35 meters with no FrameLosses, no Holds with ground range test.
In the DSMX range thread we started to believe that 1mw output power might be mapped to Spektrum trainer reduced range test mode.

I can at least tell you that this kind of behavior is not normal for the lemon RX receivers. I have a whole bunch of DSM2 6-8 channel receivers and two DSMX Sats from them that all perform great and outrange the OrangeRX counterparts.

My buddy wasn't able to meet up today, hopefully in the next couple we can get that done.

@ Arakon, I was wondering a few things about the lemon specifically. Had you heard of anyone having a DSMX RX not completing binding in DSMX mode and having to be switched to DSM2? Also how sensitive is your lemons (DSM2 if applicable) to interfeance from regular in-home 2.4ghz wifi? I was able to get nearly 15m outdoors today testing before dropout and it regained link after just a few steps back towards it. Again indoors in my workshop I couldn't regain a link till the antennas were within inches and orientated the same.


Will a sat received added onto the lemon standard RX (possibley with antenna orientated a different way) help increase range when there's background interference?

Here's a video showing how truely laughable my range is.



At this point I would be willing to ship my devo and/or RX to someone here for them to test. What's the chances of the stock Walkera module in mine being bad? And further more, could it (assuming it is tx related) be anything other than the module or would replacing that pretty much have to fix it (again assuming it is a radio issue)?

FWIW, my lemon RX's are behaving oddly as well. WIth a couple of servo's plugged in, they tend to lag behind the Tx stick movement by a quarter-second or more. Swapping them for an OrangeRX receiver solves the problem.

mwm wrote: FWIW, my lemon RX's are behaving oddly as well. WIth a couple of servo's plugged in, they tend to lag behind the Tx stick movement by a quarter-second or more. Swapping them for an OrangeRX receiver solves the problem.

Thank you for the definitive answer... So my question to you is; if it were your stuff, spending your money what would you buy first? An orange? A new Walkera devo module? A different protocol of RX?


I'm an engineer- I understand the code aspect, I understand the HW side of it, where I'm stuck is that I'm to new to this hobby to have the experience. Please guys, don't be scared of giving me the wrong answer and having it not fix it. I won't hold that against anyone, just please, some of you more experienced guys, you see my problem, tell me if it was your own stuff/money what would you go out and but first? What's your gut say the issue is?

Cereal_Killer wrote: My buddy wasn't able to meet up today, hopefully in the next couple we can get that done.

@ Arakon, I was wondering a few things about the lemon specifically. Had you heard of anyone having a DSMX RX not completing binding in DSMX mode and having to be switched to DSM2? Also how sensitive is your lemons (DSM2 if applicable) to interfeance from regular in-home 2.4ghz wifi? I was able to get nearly 15m outdoors today testing before dropout and it regained link after just a few steps back towards it. Again indoors in my workshop I couldn't regain a link till the antennas were within inches and orientated the same.


Will a sat received added onto the lemon standard RX (possibley with antenna orientated a different way) help increase range when there's background interference?

I do my flight tests either in my room, directly next to two 2.4 ghz routers, or outside near 8 or 9 wifi networks. At work I fly during break times next to 3 buildings of which one has 8 wifi networks on each floor plus a whole bunch more from the others. Never had an issue.
Sat only helps if you use it to i.e. get out of a carbon fibre canopy or to double as a secondary antenna on a large model. It doesn't actually extend the range.
I'm guessing you simply have a defective receiver or transmitter (although the latter would also mean that i.e. a devo receiver had very low range only).
I also had my lemonRX 8 Channel DSM2 receiver out 300m without signal loss.

Grab a cheapo orange or lemon receiver to verify if this is the issue.

Arakon wrote: Grab a cheapo orange or lemon receiver to verify if this is the issue.

Seconded. Since you've already got a LemonRx, get an OrangeRx one this time. HK may even have a suitable one in a warehouse near you.

Alternatively, take your Tx to BuddyRC, and see if they have a Blade 'copter or E-Flite airplane or a Spektrum Rx on display you can test against. Take your model along if you want to check a receiver. Since they sold you the LemonRx, they ought to be willing to help diagnose the problem.

Bought a orange off ebay from a different local vendor. Going to pick it up today.

Thanks guys.

Bad news, while the orange RX (R615X) does infact easily bind in DSMX mode the range isnt improved, still EXACTLY the same poor (few foot) range and dropout from stuff as thin as a cotton shirt

I guess next I need a new module in my devo? Is there anything else I can do? Any other resistors / diodes that can be bridged / removed / stacked on or anything? At this point it seems the factory module MUST be screwed so I dont mind experimenting.

Does anyone know how I can wire in this genuine spektrum tx module for testing purposes? Even if I loose other devo protocols for now, is there a way to make this work as the tx for DSMX/DSM2? If not does anyone have a universal board I could buy? I'd rather not buy a replacement devo module and have to wait 3-4 weeks.

And the factory module.

Note antenna and shield removed in this pic for testing purposes, they've both been in place for all testing.


And new video from just now showing zero improvement.

Looking at this solder blob, it reminds me of this thread.....
www.deviationtx.com/forum/3-feedback-que...each?start=120#28414
and post...
www.deviationtx.com/forum/3-feedback-que...each?start=140#28720

aMax wrote: Looking at this solder blob, it reminds me of this thread.....
www.deviationtx.com/forum/3-feedback-que...each?start=120#28414
and post...
www.deviationtx.com/forum/3-feedback-que...each?start=140#28720

I will give that a try right now however it's not actually a solder blob, it's a brass header pin.

Not saying it's a bad idea tho, I'm getting up right this second to try after all, will report back...

Edit: couldn't come up with an 0402 000 jumper but I managed to squeeze a 0603 in there. First off you're right in that the solder coated brass pin was actually measuring ~1 and 2ohms! After swapping in this jumper I zerod my DMM leads out and am measuring right at 0.000 ohms but it's still exactly the same result. I really thought you had it there for a minue man thanks for the suggestion tho!

Is this the right stock module (obviously I'll have to airwire it) or is there a direct fit 7E module I should buy instead?

m.banggood.com/Walkera-WK-DEVO-S-MOD-Upg...8S-12S-p-922596.html

Yes, this is the right one.....
www.hacksmods.com/2014/10/wk-devo-s-mod-...evo7e/#comment-34113

Edit:
.... please check the current draw before buying a new rf module to make sure the pa is not working.
www.deviationtx.com/forum/6-general-disc...-draw?start=20#24359
Left old wiring, right new wiring ( A7105-D03)...for the complete tx into Devo mode.

aMax wrote: Yes, this is the right one.....
www.hacksmods.com/2014/10/wk-devo-s-mod-...evo7e/#comment-34113

Edit:
.... please check the current draw before buying a new rf module to make sure the pa is not working.
www.deviationtx.com/forum/6-general-disc...-draw?start=20#24359
Left old wiring, right new wiring ( A7105-D03)...for the complete tx into Devo mode.

Will do later today but can you explain what you mean "to make sure the PA is not working" I don't follow...

Edit: RESULTS!
So I'm just guessing here that there should be a difference in consumption between the power output settings? That's definitely not the case, with back light on I'm getting a rock steady ~100mA (90mA with light off) on the devo module. Then I switch to an A7105 based module (non-PA A7105 pulled from a WLToys Tx) and I get 130mA draw.
Does that point to the devo PA not functioning?

[YT video uploading now, will be available shortly]


Edit2: I'm currently updating to yesterday's nightly. Dont expect any other results but I figure I should stay the course while I wait WEEKS for the new module I just ordered from banggood.
Finished, now running the 4/14 nightly (devo7e-v4.0.1-67b36f4) and everything is still the same (including current draw). Oh well, it was a thought.