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

Here is a handy tool for figuring out your link budget:

http://www.pasternack.com/t-calculator-link-budget.aspx

Also you can easily make your own antennas like the V antenna in Richard Kennedy's second post.

It isn't hard to make really good high gain antennas either like these:

http://www.wa5vjb.com/pcb-pdfs/Yagi900.pdf

Here is a good tutorial on making PCB antennas

http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-...

You can also quickly and easily make a bi-quad feed for a dish and use a surplus satelite TV dish to get outstanding links with low power radios. I have done this for Wifi links,but the idea is easily scalable to 900MHz:

http://trevormarshall.com/biquad.htm

Replies

Ivan R April 14, 2015 at 9:52am

hi...i am looking into this radio for added range....but do I need two of them, for ground and quad? or just one for TX on the quad with a regular 3DR on the ground?
- Richard Kennedy > Ivan R April 14, 2015 at 3:58pm
  
  Here's another good one http://www.droneshop.biz/900mhz-3dr-radio-telemetry-v-antenna.html
  - Joe Street > Richard Kennedy April 15, 2015 at 5:29am
    
    Here is a handy tool for figuring out your link budget:
    
    http://www.pasternack.com/t-calculator-link-budget.aspx
    
    Also you can easily make your own antennas like the V antenna in Richard Kennedy's second post.
    
    It isn't hard to make really good high gain antennas either like these:
    
    http://www.wa5vjb.com/pcb-pdfs/Yagi900.pdf
    
    Here is a good tutorial on making PCB antennas
    
    http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-...
    
    You can also quickly and easily make a bi-quad feed for a dish and use a surplus satelite TV dish to get outstanding links with low power radios. I have done this for Wifi links,but the idea is easily scalable to 900MHz:
    
    http://trevormarshall.com/biquad.htm
    
    http://www.pasternack.com/t-calculator-link-budget.aspx
    - Richard Kennedy > Joe Street April 15, 2015 at 8:10am
      
      Wow great info / links thanks!
    - Joe Street > Joe Street April 15, 2015 at 5:36am
      
      Something important to keep in mind. Typically when people who aren't RF design people (and even some that are) think about improving a radio link, the first thing they consider is upping the power. Boosting the power requires more battery, better cooling, more weight and often ugly problems start rearing up such as interference with other electronics and it may help you be heard but it doesn't do anything for your own ability to hear. An antenna that has 3db of gain is equivalent to doubling your transmitted power BUT ALSO makes your receiver hear twice as much so it benefits both directions of the link. You are always better off to spend more time, money and effort to get the best possible antenna for the job than investing in transmitter power. Food for thought.
      - Joe Street > Joe Street April 15, 2015 at 6:16am
        
        There is a really awesome highly directive yagi antenna for 900MHZ you can build at home with simple tools for about 5 bucks included in this group of antenna designs. You can mark the elements and wood boom so you can take them in and out for travel:
        
        http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf
        
        http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf
- Richard Kennedy > Ivan R April 14, 2015 at 3:55pm
  
  You can just use one on the ground and it will be noticeably better. Might want to just try this first and see if it helps you out enough. If not get one for the RX side. But also keep in mind antenna's play as much of a role as the radios do. Most of those little antenna's that come with the eBay '3dr radio' are junk. Check out some of these antennas. I noticed a huge improvement with some of these. http://store.rfdesign.com.au/antennas/
  
  Antennas - RFDesign
- Joe Street > Ivan R April 14, 2015 at 11:33am
  
  Depends on your application. If it is simplex then one should do but for duplex you have the same link budget from both ends so you better have two!
- Dennis Okeefe > Ivan R April 14, 2015 at 11:20am
  
  As I understand it you only need one - TX for sure. Folks say it works better with two however....
  
  dennis
Bill Isenberger March 14, 2015 at 6:07am

I got this error message in Mission Planner 1.3.16 when I tried to update the firmware on my RFD900P.

I hit the Yes button to report the error.

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