I am having problem with upload command from flight data. Eg Change altitude, restart mission ect. I do not have this type of problem with the previous Mission Planner. When I try to change altitude, a fail massage window appear. I also can not write param to APM while flying. But if the plane had landed and close by my computer, there is no problem. Anyway I can establish connection between the two data modem with ease.

I'm using RDF900,  am I doing something wrong in 3dr radio setting ? Thanks for your help.

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If you didn't change your RFD900 settings, it should work as before. Is your RSSI and link quality good in the air?

The link quality is very good, more than 95 %. For the recent flight I just fly within a few hundred meter at 100 meter altitude.

I do a test flight this morning with two notebook. One with the recent Mission Planner another is older .62 version. Both have the same problem. I can change mode from flight data action tab when the plane is close to me. Once in the air, nothing can be done. I have 90 to 99 % link. 

Is it some param setting problem with my RDF900? 

Did you ever figure this out? Also I was thinking of getting a RDF900 have you been happy with it? What range do you get. Thanks!


RFD900 works great. At the moment I use the RFD900 on ground and 3DR in air. Getting over 4 miles.

I am hoping to get a solid signal at 6 miles. Seems like if it gets 4 with only the ground station side with one in the plane too it should get 6. Hope so!  

You can Google and find the RFD900 will get over 20 miles easily if you have them on both ends of the link.

Hi Steven,

I'm having range problems with my RFD900 - perhaps you can help. Could you post your settings perhaps?

If you have the time here are details on my issue -> http://ardupilot.com/forum/viewtopic.php?f=94&t=7811&p=1740...

Your settings look okay but I would change the airspeed to 64. Use the tool on the RFD900 site and set to default values to be sure. http://rfdesign.com.au/downloads/

You also realize your Tx and Rx power settings are not maxed out, which would be 30dBm. On the ground side you shouldn't have a problem but in the air you may be better off with your lower setting due to the impact on other RF sensitive devices, like the GPS Rx.

Here is what I see as your problem. If the picture is correct or I should say if I'm seeing it correctly, your airborne antenna are going to be out of phase with the ground antenna. In fact, they would be the worst possible way to have them. The ground, which should be the longer 1/2 wave dipoles, need to be roughly vertical. The smaller 1/4 wave monopoles on the Air modem need to vertical as well. Both antennae can be in a slight V to help keep max polarity while the plane is turning. Hope it helps. If not, reset to defaults and try again.

Also, local noise on the plane will not affect the ground receive, only the Air receive and vice versa. It's another way to check where your noise is. But from your plot, noise looks low. Change the Rx antennas to vertical...


Thank you for your reply, very much appreciated! I will make this change immediately.

Should I be using both antennas on the air side? As i was searching around I see people use 1 on the air side; not clear why. 

In the manual it says:

They are required to be mounted on a ground plane of approx 20cm diameter

or more to operate as intended.

 Does this mean I should be taking a 20-30cm piece of copper tape and stick it on the bottom of the airplane, with a peice of the copper tape touching the ground of the antenna?

You can make a ground plane but really not necessary. I would use two antennas. Sometimes you can get a strong on board signal and lock onto the side without the antenna. Of course you would then be screwed as far as getting signal from the ground RFD900.

This is the antenna you should be using. http://store.rfdesign.com.au/antenna-900mhz-2dbi-right-angle-monopo...

With the one you got, you will have to mount the whole unit vertically. I don't know why they don't give people a choice when purchasing. When I bought mine, long ago, I asked for the 90 degree antennas.

awesome - I did recently order those antennas so I have these two: they look different than what you linked.

And as for the ground plane - i'm glad it doesn't make a huge difference, but in the position I am in now +  the use of "required" i'm inclined to try.. just to be sure:

-can I put this 20cm diameter copper ground plane on the base of the wing, under where the rfd900 is mounted? or does it have to be literally under the rfd900?

-does it matter if I physically connect the ground plane to the ground of the antenna?

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