Hi All,

Has anyone experienced range problems with the 433Mhz 3DR radio?  I get a solid initial connection but I can only get about a metre of distance before the signal drops out. I also have a 915Mhz radio and that works fine.

Here are the current settings. The remote also has the exact same settings.

I am hoping it is just a setting I have not set correctly.

Thanks

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Are you using the base station transceiver with the integrated USB FTDI? That had some known issues with interference...

No. I have two air modules as sold in the 3DR store and am using the provided USB cable to connect to my pc.

Tx Power

I have both set to 14. The maximum I am allowed in Aus.

Dear Michael,

I have the same problem. Both modules (locale and remote) do connect fine each other but I only get about 50 m range before rem.rssi drop down to cero. I have tested several configurations of air speed and TX power, and even with air module completely outside the airframe but all unsuccessful. I don't know what else I can do. I am still looking for a solution

I noticed in the picture that you're using firmware version 1.5.  I believe the current firmware version 1.6.

-Mike

Hi Michael,

You should get much better range than that. Can you post a tlog of a range test? Start it up with the air radio and GCS close to each other, and with GPS lock on the air side, then walk it away and the tlog will allow me to see the signal and noise levels on both ends.

There are lots of possible causes for why range would be poor. The two most likely are large noise levels (eg. USB noise) and antenna connector problems (eg. using SMA antenna with RP-SMA radio).

I've also seen cases where the power amplifier has been damaged by transmitting for too long with no antenna attached (or an antenna with the wrong connector).

Cheers, Tridge

Hi Tridge,

I think I have the same problem. Yesterday I was testing radios on the ground and I also updated firmware from 1.5 to 1.6, but I didn't notice any improve in range. I lost signal after 40-50 m.

You can find here uploaded two tlog of range test before and after firmware upgrade. In both cases I left the airplane on the ground and I moved GCS with my car for 25-50 m and then I got back.


Cheers,

Eladio

Attachments:

Hi Eladio,

It is better in a range test to move the aircraft instead of moving the GCS, as that way I can get a plot of signal versus distance (by looking at how far the GPS position moves). Here is the plot anyway for your first tlog:

the main thing we can see in this is that the noise level on the ground radio is significantly higher than the noise level in the air radio. The difference is about 12 RSSI, which is around 6dB. A 6dB difference makes a difference of 2x in range.

Now let's look at your 2nd log:

that log shows the opposite problem, which is strange. Did you swap the two radios for these two tests? Or did you swap antennas? The firmware change should not have affected the signal level.

You also mentioned that you moved the GCS "with my car". The wavelength of these 433MHz radios is around 70cm. If you have them in or close to a car the performance will be very poor. You want both radios to be well clear of the ground (at least 70cm, preferably more), and well clear of any metalic structures.

Also, what transmit power level do you have set on each of the radios?

Cheers, Tridge

Hi Tridge,

Thank you very much for your analysis. I agree that is better to move the aircraft instead of moving the GCS but I was alone and it was easier to do it in that way and also because I could see the evolution of RSSI values by MP tuning. Regarding the distance, as it was so short I could estimate directly by sight.

Well, regarding your questions:

1st log-  ground radio is connected to my Tablet PC by a the original FDTI cable so it should minimize noise contamination from the laptop (in teory).

2nd log- you are right. I swapped both the two radios and antennas between tests (sorry for not mention it but I was doing too much changes, although I recorded all combinations in a paper notebook and when I did each one, so I can check it out now). So, in relation with my previous comment, does it means one radio (the ground one in the first test) has a noise problem (not noise from the laptop)? or an antenna?

And I set the "Ground" radio in the roof of my car during tests, so it probably affected the quality of the signal. Anyway, when flying in "normal conditions" I usually install the laptop in an folding table and the radio in the top of a metal tripod, but mounted over a foam piece (not directly attached to the metal). Maybe I usually seat down no enough far away from my car (aprox. 1 -1,5 m because I use its shadow) but I suspect that car effect by itself should not be so important to explain the really poor performance of my radios.

On the other hand, in both tests radios were transmitting at maximun power (20db 100 mw). One interesting thing is the rapid and step drop of remrssi in only 20-30 meters from GCS

Hope all this help you to perform a diagnostic or a way to find the problem.

And all your comments are very usefull for next tests and for everyday deployment of the system in the field.

Thanks again,

Cheers, Eladio

Hi Eladio,

Can you try one more test for me - this one you don't need to go outside for.

Setup both radios to transmit at 20dBm, and run them at a distance of 1m apart, with both antennas pointing up. Open up mission planner and the 'status' tab under Flight Data.

With the two radios 1m apart, look at the "rssi", "remrssi", "noise" and "remnoise" numbers, like this:

With both radios at 20dBm and about 1m apart, I'd expect the signal numbers for both to be around 200 RSSI.

The reason I'm asking you to do this is that the high part of your graph, where you presumably were standing very close to the plane, was only 120. If you were within 1m or so of the plane at that point then something is badly wrong.

If you don't get a number close to 200 then it means that either your antennas are not working correctly (eg. they aren't 433MHz antennas or the connectors are not right), or your radios are damaged. For example, if you had been running a radio with no antenna attached then the PA (power amplifier) in the radio could be burnt out. I had that happen to one of my radios when I accidentally ran it with the wrong type of antenna connector, so the power reflected back into the radio and burned out the PA.

Cheers, Tridge

Hi Tridge,


I'll do that test and I'll tell you but I think that I have never reached a RSSI value over 200

Cheers, Eladio

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