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

Hi Seppo

Help me to understand a little more how these things work.

When you say

1. "Telemetry plus concurrent PPM passthrough." what does that exactly mean? Same modem ca be used for different functions?

2. "Modems with higher data rates and encryption (finally) are in the works." What is the advantage of these features?

My additional question is that, I figure that some GSM networks use the same band 900MHz, or even other broadcast could be using this band or near it. Now remembering from when i was a child, we grew up near the border with Malawi, some of National radio Channel when listening to the radio, you would also hear in low voice in the background another channel talking. I remember back then radios had a fine tuning knob, so to get rid of the background interference we had to fine tune with the fine tuning knob. In the AUV operations how does interference with other broadcast that may be using same band or nearly same band play part? is there even interference at all? Enlighten me a little on this one please!

Replies

- IronDOME > Seppo May 11, 2016 at 11:53am
  
  Hi Seppo
  
  Help me to understand a little more how these things work.
  
  When you say
  
  1. "Telemetry plus concurrent PPM passthrough." what does that exactly mean? Same modem ca be used for different functions?
  
  2. "Modems with higher data rates and encryption (finally) are in the works." What is the advantage of these features?
  
  My additional question is that, I figure that some GSM networks use the same band 900MHz, or even other broadcast could be using this band or near it. Now remembering from when i was a child, we grew up near the border with Malawi, some of National radio Channel when listening to the radio, you would also hear in low voice in the background another channel talking. I remember back then radios had a fine tuning knob, so to get rid of the background interference we had to fine tune with the fine tuning knob. In the AUV operations how does interference with other broadcast that may be using same band or nearly same band play part? is there even interference at all? Enlighten me a little on this one please!
  
  ID
  - kent Martin > IronDOME June 4, 2016 at 9:22pm
    
    ID,
    
    1. PPM is a pulse coded output that holds R/C channel information about servo positions. It is a single pin output that can be interpreted by the filght controller to read the positions of your Radio control stick/switches/etc. What is it for? Well if it is used and you have a flight controller on board, then you will no longer need the R/C receiver, or the R/C transmitter. It will need some small circuit to interface to the output of your R/C controller. We'll be working on that, or users can hack some simple resistors to try it out. The ppm input/output pin is separate to the serial input output pins, and both ports can be used at once.
    
    2. Higher data rates? Well why not, but seriously there may be many people who want this, for example passing low quality video, or just more/faster rate data they want to pass to/from flight controller. Of course there's always a loss of range with higher rates, but usability depends if it is still within your requirements at the desired rate. Encryption? Well I guess just link visibility is an issue for some people.
    
    Kent
  - Dan Ho > IronDOME May 11, 2016 at 12:24pm
    
    Hi ID,
    
    A good thing about these modems is that they use spread spectrum whereas GSM is narrow band. When a spread spectrum receiver de-spreads the incoming signals, narrow band signals are significantly spread out and therefore reduced while the desired spread signal from the RFD modem is increased. In other words the RFD modems should not be impacted too much by GSM signals, even if their frequencies overlap, IMHO.
    
    Dan
    - IronDOME > Dan Ho May 11, 2016 at 12:42pm
      
      Thanks for this clarification mate
      
      Would you have any comments about the first two questions?
      
      ID
IronDOME May 9, 2016 at 12:13pm

Hi Seppo

Whaat does this statement mean "Long range >40km depending on antennas and GCS setup.". What GCS setting and antenna would ensure this range?

Thanks in advance
- Admin
  
  Thomas J Coyle III > IronDOME May 9, 2016 at 12:15pm
  
  @IronDOME,
  
  It might imply a tracking antenna mount controlled by the GCS and a Yagi antenna.
  
  Regards,
  
  TCIII AVD
  - IronDOME > Thomas J Coyle III May 9, 2016 at 12:19pm
    
    Thanks Thomas for quick reply.
    
    So, would Yagi antenna be better than that the Omni? If so would you recommend which make and model of the yagi? I am preparing to assemble an X-Talon so presently I'm putting together a list of what is needed.
    
    Thanks once again.
    - David Boulanger > IronDOME May 9, 2016 at 12:29pm
      
      IronDOME,
      
      Antenna theory and matching components properly is something you may want to look into. A Yagi is directional and the Omni is not. It also depends on the airspeed, duty cycle, and a variety of other factors you program into the radio.
      
      Regards,
      
      David R. Boulanger
      - IronDOME > David Boulanger May 9, 2016 at 12:34pm
        
        Hi David
        
        Your advise is really appreciated, thanks; as you have been aware that this no field of my expertise. In this case I think I will for now stick with Omni using the RFD900 modems.
        
        Many thanks.
        
        David Boulanger > IronDOME May 9, 2016 at 12:42pm
        
        I'm no expert. Read as much as you can and there is a lot to learned on YouTube video's about antenna's and matching equipment properly. The antenna's that come with the RFD seem to be of good quality.
        
        Regards,
        
        David R. Boulanger

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