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

This is a basic RF theory question, nothing specific to the RFD900.

You need to calculate a link budget; there's plenty of information available online, and there's even a calculator I found with little effort (http://www.afar.net/rf-link-budget-calculator/).

The minimum information you need is your transmit power (in dBm), the gain of your transmit and receive antennae (in dBi) and your receive sensitivity (which from the RFD900 specs is -121dBm for low bitrates.) Using that calculator I can easily get 25km even with really low gain 2dBi omni's on each end and not even full transmit power.

If you needed antennae with higher gain in order to get the distances you need, then you'll have to look at the beam patterns of the antennae and ensure they overlap at your max distance. That's basic geometry.

Beyond that, you actually have to do physical testing at your location to determine the best configuration; theory only goes so far.

Replies

- Ivan R > Karthik July 15, 2015 at 6:53pm
  
  would definitely use a yagi on GC.....
- James Churchill > Karthik July 15, 2015 at 1:18am
  
  This is a basic RF theory question, nothing specific to the RFD900.
  
  You need to calculate a link budget; there's plenty of information available online, and there's even a calculator I found with little effort (http://www.afar.net/rf-link-budget-calculator/).
  
  The minimum information you need is your transmit power (in dBm), the gain of your transmit and receive antennae (in dBi) and your receive sensitivity (which from the RFD900 specs is -121dBm for low bitrates.) Using that calculator I can easily get 25km even with really low gain 2dBi omni's on each end and not even full transmit power.
  
  If you needed antennae with higher gain in order to get the distances you need, then you'll have to look at the beam patterns of the antennae and ensure they overlap at your max distance. That's basic geometry.
  
  Beyond that, you actually have to do physical testing at your location to determine the best configuration; theory only goes so far.
jean-luc July 6, 2015 at 6:09am

Hi Seppo,

I receive my RFD868+ bundle.

But when i'm connecting the modem with RFDtools 1.5, i can't see and change the 868Mhz frequency, i have only the choice between the 902/928Mhz band.

Is there an hardware frequency band error with these modems or i need another software tool for configuration??

Regards,
siyamand moloudnejad June 20, 2015 at 11:26am

thinking if i can hook up my tx "which is running uhf433" to this data radio and get rid off uhf 433. is that actualy possible i have searched alot about it and still searching. feiyu-tech is selling remote adapter which can be connected to the rx and the fy-60X after a certain range controling plane over datalink. but not sure if its gonna work with RFD ? anyone?
Ivan R June 10, 2015 at 11:43am

all sudden my RFD900 range has been drastrically reduced to a few hundred meters and I cant figure out why? I tried resetting all parameters to default, reflashing the firmware, checking all connection and no luck....what would be some reasons for this?
- Admin
  
  Thomas J Coyle III > Ivan R June 10, 2015 at 11:53am
  
  @Ivan R,
  
  Maybe the final power amp in the transmitter section is failing or the sensitivity of the receiver section has fallen off drastically. Since you have reset all parameters to their defaults, it is probably not firmware/programming related.
  
  Regards,
  
  TCIII AVD
- Raph > Ivan R June 10, 2015 at 11:47am
  
  HI Ivan,
  
  Many things can cause this, usually interference from other devices on your copter. Check for any new equipment you may have installed (BEC's, VTX's etc), and start unplugging them until you find a cause. Good luck!
arga firmansyah May 21, 2015 at 6:18am

I have RFD900 both on the hexa and the ground control. TX power from the default setup is 20dbm. I have tried to change the tx power to 30 dbm with success but unfortunately it can't connect on mission planner if the tx power is 30 dbm.
I have tried to use 30 dbm only on the ground while the air unit 20dbm but still can't connect. It can only connect on mission planner if both has 20dbm tx power.
Is there anything that i missed?
- Joe Street > arga firmansyah May 21, 2015 at 7:24am
  
  you could try putting some Ferrite beads on the communication leads as close as possible to the ends. It could be that RF that strong is coupling into the com lines and causing the problem. If you can shield the boards it might also help if this is the cause of the problem.
  - arga firmansyah > Joe Street May 21, 2015 at 5:00pm
    
    Somehow i'm not really that will help, but will try that this weekend.
    I have try to use 3 different computer and came out the same result.
    I have 2 hexa and both of them bahave the same as well.

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