The product page for the 3DR radios is full of bogus specs!  Could you please post the REAL specs?

For example, the page claims "Receiver sensitivity to -121 dBm".  That is the spec for the SiLabs chip radio.  HopeRF lists the specs for their radio module as significantly less sensitive, and obviously you can't obtain the spec of the module when used within another product, like the 3DR radio.

Also, what's with the range claims?  I see you've changed it at least once, but why not make a realistic range claim.  These radios should do around 8 km.  So why only say one or a few?  Have you really not properly tested them over a few km?

Also saying "with Si1000 8051 micro-controller and Si4432 radio module" sounds like the product page writer may not have a good grasp of the hardware.  It has one Si 1000 radio chip in it.  I guess you can argue that statement is sort of true, but it certainly could cause someone to misunderstand and think it has two chips on board.

Don't take this as a rip.  I just see a lot of radio retailers out there that either flat out lie about the specs or have such a poor understanding of the technology that they mistakenly put wrong specs.  I don't think DIYdrones is either of these, so I thought I'd offer some constructive criticism to help you guys get going.

I also kind of feel responsible since I recommended using these chips in a radio design in several posts last Sept..  So if you need any help, just ask.

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Polarity is usually about 3db.  That is, antennas parallel to each other get about 3db better signal than crossed antennas.

The radiation pattern of an omni like the sock antennas looks like you dropped a doughnut right over the antenna.  


Where are you flying?  country area or city...

I routinely fly 1.5 miles in the country on the 915 Mhz radios.. stock antennas

default settings,   You must have interference with other parts of your gear or from somewhere.

I think the 433 should maybe go farther than the 915...

Can you try moving your antennas?  the ground one should be high as you can get it and away from other ground station things.  the one on plane.. maybe just move it as far as you can from  whatever is the closest transmitter to it?


The xbee pro in the store claims, "Up to 6 miles (10 km) RF LOS with high gain antennas"

That's not outrageous. I had 14 km with a pair of XBee Pros. Antennas were a quad biquad that I had put together without any kind of testing it for the ground end, and a simple stripped-coax quarter wave GP at the UAV. It wasn't a very reliable connection but it was a connection. The problem is, of course, that I had to fly quite high to stay within line of sight from the ground station and this might not be what I wanted to do or was allowed to do.

Now I use GPRS mobile data with my home made code library.

As an radio amateur, I had 2 way conversations between Denmark and England a few times, while with the same radio and same antenna I had problems reaching people in the other end of town.

There is not really any such thing as range... just good or bad equipment and ditto conditions.



Hi guys,

I have been away for a year and just picked up a couple of apm 2.5 kits. All i can say is wow! Amazing progress on the multirotor performance!

I have two 3DR kits 900& 433 an unfortunately i would be lucky if i got more than 400 ft with either - my settings are exactly above for the 900 version. It seems some are getting excellent results with stock antenna and some (like me) are getting very poor range.

There must be some other factor???? In the 3dr radio application, my floor noise is about 30-40 at most and my 900 signal value is about 160 with the quad 2 feet away. The signal drops rapidly with distance. I assumed it was poor antennas but even with a good 900 rubber duck and a 900 patch, i am seeing similar results.....

Is it possible that some of these radios are transmitting at a significantly lower power than those that seem to be working well???

I am at a loss - i have several xbees and they have readonsble range - albeit at significantly greater cost

Any advice would be greatly appreciated!


The 433MHz band is really polluted in Europe. 433,92MHz is the standard frequency for wireless switches, garage doors and a million things more, like traffic lights, industrial remotes, etc. Add to that interference from PCs and stuff... LPD radio, PMR radio...

If you have a scanner or wideband receiver, monitor the spectrum - you'll be surprised.

Now, remember that a plane is in the air, that means, it's in line of sight with all and every source of interference in a wide area.

433MHz - in my opinion - is absolutely unsuitable for long range telemetry in Europe, at least, with license-free power levels. 868MHz should be much better there.


There's a paper from Trafi which recommends 868MHz for UAS telemetry in Finland.

wow, that is high for the ground antenna, so I doubt that is the problem, haha.

No , I just left the number of channels at whatever was default.  I see other people having low ranges too. I don't know whats the difference.. I guess I have to be glad I got good radios or something?

Those look pretty interesting:

XBee-footprint, encryption, ... and you can easily remove the whip and solder an SMA connector on.

You probably got a lemon.  The radios range should be measured in kilometers, not feet.

The Chinese modules used on the 3DR carrier boards can suffer from quality control issues.

And who knows, maybe you even got the wrong frequency module.  I'd send them back since it's pretty difficult for you to do any real testing without a lot of RF gear.

Would an ezUHF conflict with the 433MHz module? It's possible to change the power level in the firmware or only with external amp?


Just as a FYI. Today I was able to go out and get a good solid 1km out of the telemetry set. This is up from the sketchy signal I was getting at 500 meters. On the ground I'm using a 3dBi antenna from L-Com..

In the air I'm using the standard stock antenna. Both radios were set to an air speed of 24, down from 64. I'll test out to 1.5km next weekend. 

I've measured the active element of the 3DR 433MHz antenna at 42mm (1.65") but it's coiled (see pic). 160mm should be quarter wave for 433MHz so does the coiling make 42mm equivalent to 160mm, would uncoiling it make it better?

Probably a dumb question, but I couldn't find the answer anywhere.  For the stock antennas that come with the 3DR, which way should they face?  Right now, I have them both pointing up.  One comes out of the laptop and points up, and one is mounted pointing up on the copter  Thanks!

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