I recently dropped a line to the DIYDrones store folks when I noticed that images posted for the 915Mhz Air module in the store are different to the ones in the documentation and also picture shown of this module in the 3DR Telemetry kit.  I am mainly interested if there was an change in the design / version release of the hardware and would like to know what is shipping currently?  In other words is there an updated air module to correct some problem?  Below are the comparative images. You can clearly see the main board in one version is purple and the other is green.  What is clearly evident is the orientation of the HM-TRP module.  For the all green circuit board design (photo shown in the store for the 915 Air module on its own) the HM-TRP module connector is parallel to the main board edge connector (FTDI-style pinout).  In all the other photos of the Air module (included in the kit photo and manual)  the HM-TRP module is oriented 90 degrees to the FTDI-style pinout.  

I can make out v1.2 on the all green board.  But cannot see the version on the purple main board version with  HM-TRP module on top and at 90 degrees to the FTDI-style pinout.

I just want to understand why there appears to be two different versions of the 915MHz airmodule? Does anyone know? When I tried to get a sensible answer from the store contact they thought I was referring to the air and ground module.



Note the differences between the HM-TRP component orientations in the above two images of the same item (3DR Radio Telemetry 915MHz Air Module).

Has anyone recently received their 3DR radio kit and can confirm what version of the air module they have.  I have not picked up on any other forum discussion on this.  Somewhat of a mystery to be solved.


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Today I received my 3DR 915MHz Radio Telemetry kits, but both appear to have build quality issues.  I firstly want to point out the diydrones folks do a fantastic job in providing these products and I am sure I can fix the problems, so I don't want this to be taken the wrong way.  Below is a photo of one of the ground modules I received and the main problem is the soldering or lack there of in places.  In the photo below you can see solder missing on some of the pads (near the usb connector) and there is excessive flux and overheating signs on the antenna connector.  I compared this to the store photos and there are no signs of this issue. One of my main concerns is the HM-TRP module which on all 4 boards is not lined up with the main board pins and there is virtually no sign of soldering filets between the upper and lower board in some places.  So I am concerned about reliability, with a little in flight vibration over time.

In this post I had asked about the two different board designs and it would appear there are build quality issues with the later model (green board) modules.   I will have to re-solder all the modules to fix the issues.  The tricky bit will be the HM-TRPmodule. Perhaps it would have been better to take more time building the purple style boards versus using a fast build process for the new version and different HM-TRP module orientation?

A few other issues I noted include the right angled pin edge connector which is supplied with the Air Module.  Instead of the gold plated pins shown in the 3DR Radio Telemetry documentation a tin plated alternative is supplied.  I will need to go out and buy a suitable replacement.  Again no big deal but annoying not getting the quality expected.

Finally could someone comment on the current telemetry antennas supplied.  They store notes say they will swivel but the four I received are all fixed and I dare not try an turn the screw base for fear of braking the internal antenna wire.  So for now when I screw on the antenna I am stuck where the antenna points as it appears it cannot be turned?  

So a few issues for the suppliers to sort out.  Hopefully I can re-solder the boards to fix the issues.

Another quick question.  Does anyone have photos or notes on how they mounted the 3DR telemetry radio on the arducopter?  The air module is tiny and unlike the xbee pro does not have any way to nylon screw fix the circuit board to the frame.  Also because the surface mount components are so delicate I would not risk using tie traps. I thought of using a piece of double sided tape but worry the sheer weight of the antenna, when the arducopter is flying and accelerating, might break off the antenna connector or lift the board off.

Its worth noting the ground module version I received in both kits is version 1.0 and the air module is marked v1.2  I assume this is related to the air module design change and the ground module remained the same?  I certainly hope there is no version mismatch.

Hi Greg, I'll try to address your concerns.

Re: the version numbers, the version numbers printed on the boards indicate physical design revisions and have no relation to the firmware version. All 3DR radios, air and ground modules, are compatible with each other, provided all of them are running the same firmware.

Re: mounting the air module, you should have received a piece of clear shrink tubing with your radios, you can use that along with some double sided tape or velcro (what we use). We have not experienced any problems with the antenna and antenna connectors.

Re: the antennas, they do swivel but it's a bit tight. You can see that when you swivel it, the antenna wire rotates with the plastic casing, as does the center pin contact inside the connector. The wire doesn't twist.

Re: the build quality issues, all radios are functional when they leave the warehouse. If you are having problems with the radios you can email help@3drobotics.com. Regarding the HM-TRP module solder, the reason you don't see a filet on the solder joints is because during reflow the solder accumulates inside the through-hole part of the pad instead of against it's side. There is sufficient solder on the joints though. I've attached a photo that shows the size of the pads on the bottom board.

Sam thank you for the clarification on the board issues I raised. I did look at all my boards and even the through hole soldering is non-evident in many of the holes.  I had considered this before I wrote my previous post.  It could be ok as you say, but though I better highlight it. If your happy I am happy :-)

If you do have a photo or anyone for that matter of their mounting of the air module, that would be appreciated.  I plan to do some testing today and will let the group know how it goes.

Any news on 915 MHz availability? It’s need quite a while since I have seen any news. Any estimates on when it will be available?

I saw the same issues you mention with mine.  This is typical of Chinese made boards.  There's really nothing to worry about.

These are IPC class 1 boards.  If they work they pass, there's no quality control on the soldering whatsoever.

I thought about redoing mine, but ended up deciding it was more of a risk and waste of time than it was worth.  If I were producing a commercial end-user product I would certainly try to hit class 3 standards, as that is what is appropriate when you're putting injuries and significant investment at risk.  However, it's not too bad for experimentation and as a first stab at a cool new product.

There's a few design issues I've pointed out and I'm sure they'll redesign a bit for the next major hardware revision.

Since you've got soldering skills you might want to order a few HopeRF modules as spares or to do your own board.  They're only $10, and with a little bit of coax to a bulkhead RP-SMA connector and a couple resistors for 3.3->5v signal matching you probably don't need the 3DR carrier board.

Hey Jake,

Thanks for the good tips on putting together a custom module.  Having a steady hand at soldering does come in handy sometimes.  Like you I thought long and hard about the re-soldering and in the end it was tempted to see if I could get away with it :-)  I will certainly get a few spare modules for a rainy day as they say.  Cheers

Hi Jake,

Where to get the HopeRF modules? I've only found them in Europe for $16 plus shipping.



Try http://www.hoperf.com/

They quoted me $10 each.  That was just for 1 unit.  If you want a dozen or two you can probably get a small deal.

Just remember that the Si1000 needs 3.3-3.6v (maybe 3.8 max).  So you will need to add a resistor/regulator/level shifter or the like in your cable.  Or you could build your own carrier board.

Are the 900 radio sets every going to be in stock? I have been waiting for a very VERY long time but it always gives me that goofy WHOOPS!  message.

They should at least open it up to per-orders so I can get one when they are back in stock.




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