RFD900, RFD900+ - New long range radio modem - Discussions

Hi All,

I would like to introduce you to a new radio modem that we developed for very long range datalinks!

http://rfdesign.com.au/RFD900.php

Some of the key features of the RFD900 are as follows:

Multi point and point to point link capability.
Long range >40km depending on antennas and GCS setup.
2 x RP-SMA RF connectors, diversity switched.
1 Watt (+30dBm) transmit power.
Transmit low pass filter.
> 20dB Low noise amplifier.
RX SAW filter.
Passive front end band pass filter.
Open source firmware / tools, field upgradeable, easy to configure.
Small (30 x 57 x 13 mm), light weight (14.5g).
Compatible with 3DR / Hope-RF radio modules.
License free use in Australia, Canada, USA, NZ.

These modems are designed to support long range applications, while being easy to use and affordable.

These modems have been flying in various platforms and have demonstrated excellent performance in real applications.

RFD900 modems are now available at: http://store.rfdesign.com.au

Support within APM planner and the radio configurator from Michael Oborne is already available.

It works seamlessly with APM planner, all radio Mavlink parameters are available.

Update, December 2014: The RFD900+ with improved specifications is available now at:

http://store.rfdesign.com.au/rfd-900p-modem/

Seppo Saario

rfdesign.com.au

Dear all,

I have two questions regarding the ¼ wave length monopole antenna that comes with the RFD868+ and ground plane. Thankful for any comments!

- The antenna:

http://store.rfdesign.com.au/antenna-900mhz-2dbi-right-angle-monopo...

1) The antenna needs accoring to the description a ground plane for optimal performance, but how do you usually mount the GND plane when the connector is 90 degree turned?

2) We intend to use the RFD868+ radio modem on a flying wing for long range telemetry and I am considering different antenna options. My question is, if I place the monopole antenna facing downwards and add a ground plane, then I will gain in antenna performance (compared to no GND plane) but this will also restrict the radiation to the lower part of a sphere centered at the airplane. So as soon as I am in a rolling motion turning towards me I will have zero connection since the ground plane is between the transmitter and receiver. Is this something any of you have experienced and if so how do you usually mount the antenna and the ground plane to avoid it?

Thanks!

Replies

James tate August 10, 2015 at 3:50pm

Got mine already wired in to a 3DR Pixhawk, but connecting to the usb cable to Laptop on Base station it connects at Com Port 6 57600 but I get a error message saying;

"Failed to load Command Mode"

And the Led on the 900+ stays Solid Red.

What's happening ??
Dan Ho August 10, 2015 at 12:42pm

Hi Carl,
I've never added a special ground plane. The cable shield acts as one half of the antenna so that, although it's called a monopole, it's really a dipole. If the antenna and cable are mounted so that they are in-line, the radiation pattern will be fairly omni-directional. But for your antenna, the cable is probably at a 90 degree angle to the antenna which is going to have a lopsided pattern that's stronger in some directions than others. I've always used tranceivers that have two diversity antennas like the RFDs and mounted them at 90 degrees to each other with one vertical and one aligned horizontally along a wing. This has given very good reception regardless of the plane's orientation to the ground station. If you do add a ground plane, then I would think it would be best to mount two of those antennas at 180 degrees from each other, on opposite sides of the ground plane. But I don't know why go to all the trouble (plus add the extra weight) when there are easier ways to do it.
- Ikaros > Dan Ho August 11, 2015 at 12:55am
  
  Hi Dan,
  
  Thank you for the comments. I will start without ground plane and see if I can improve the performance later after some range tests.
Ikaros August 9, 2015 at 11:28pm

Dear all,

I have two questions regarding the ¼ wave length monopole antenna that comes with the RFD868+ and ground plane. Thankful for any comments!

- The antenna:

http://store.rfdesign.com.au/antenna-900mhz-2dbi-right-angle-monopo...

1) The antenna needs accoring to the description a ground plane for optimal performance, but how do you usually mount the GND plane when the connector is 90 degree turned?

2) We intend to use the RFD868+ radio modem on a flying wing for long range telemetry and I am considering different antenna options. My question is, if I place the monopole antenna facing downwards and add a ground plane, then I will gain in antenna performance (compared to no GND plane) but this will also restrict the radiation to the lower part of a sphere centered at the airplane. So as soon as I am in a rolling motion turning towards me I will have zero connection since the ground plane is between the transmitter and receiver. Is this something any of you have experienced and if so how do you usually mount the antenna and the ground plane to avoid it?

Thanks!

Antenna 900MHz 2dBi Right Angle Monopole (RPSMA)

RFDesign designs and manufactures the Antennas, RF Electronics and the RFD900 radio modem
juan pablo gayoso August 6, 2015 at 4:42pm

I have a RFD900 modem Bundle working in my UAV. Now, I am build a new DIY UAV, so my question is: can I use my old RFD900 modem as ground station, and binding with new RFD900+ version in the UAV. It mean that my present Ground modem will be working with both UAVs, one at time?...it will be possible?
Ikaros August 6, 2015 at 8:51am

Hi,

I have another question regarding the AT commands. Now when I connect the FTDI cable to the modem and write '+++' I get 'OK' back. However, then when I try any command, e.g. ATI5 I only get the exact same letters back and no information. Is this normal operation and I am missing something?

Thanks in advance!

Regards,
- James Churchill > Ikaros August 6, 2015 at 7:19pm
  
  The +++ mustn't have <enter> after it, but the AT commands need it! Did you change your serial console settings back after you got into AT mode?
  - Ikaros > James Churchill August 9, 2015 at 2:35am
    
    Thanks again :) now it works!
Henri August 5, 2015 at 10:54am

Much better link than the 3dr modem.

Seppo: I do have a number of RFD900 and they all perform very well except one.

As I was setting the channel number and other various parameters through mission planner, the on board LED got solid red and nothing I have tried changed this?

It is the new version (black PCB with version I written).

I even downloaded RFDtools V 1.5 but it looks like this one refuse to communicate.

What should I do?

Thanks and regards

Henri
- Henri > Henri August 6, 2015 at 5:38pm
  
  Perhaps Seppo took long holidays in a paradise island?
  
  :-)
  
  Henri

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