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

Nice work! The 3DR radios are decent, but they didn't really incorporate that many of the features I had initially planned when I proposed the idea of creating a Si1000 based telemetry radio. They chose to go with the HopeRF module instead of creating an original design or using the reference design. It's good see there's still some good engineers out there willing to do more than slap a module on a carrier board.

A few questions come to mind...

Have you done any tests to check your actual receive sensitivity? 3DR claims to have a sensitivity even higher than the HopeRF module they use, despite the fact that I pointed out how foolish and obviously false that claim is.

Which amplifier chip did you use (RMFD, Skyworks, Maxim, etc.)? Or did you use a discrete design?

Is there a passthrough? That is can you turn the amp on and off?

Can you vary the RF output by changing the Si1002 output? Or is the amp gain controllable in some way?

How much current does the unit draw at various output levels?

I see there seem to be at least 6 pins exposed. Have you thought about using your unit as a RX replacement? That is do you think you could output PWM or PPM or even some simple relay/GPIO control?

Sorry to hammer you with so many questions, but it looks like you've actually produced a unit very similar to the one I envisioned and suggested on this forum last September and I'm excited!

Replies

Seppo July 4, 2012 at 9:39am

What kind of range can be achieved?

We did some preliminary tests with the radios at full power, 1 Watt to see what is possible.

This was of course done in the middle of the night in the freezing cold (Winter in Brisbane, Australia).

One radio was on Mt Cootha, just to the northwest of the city, and the other radio was out of a car window on a wooden stick, connected to a laptop. (at ground level). This is quite nasty for multipath and noise at ground level.

We achieved a bit over 25km with this configuration, at standard air data rate settings (64k).

The picture below shows the two locations where we had a stable link.

The range can be significantly improved with getting the antennas raised above ground level and reducing air data rate which will reduce noise in the receive channel due to narrower filters.

The antennas used were the standard 1/2 wave dipoles at each end of the link.

Next tests will be to an airborne platform, with the GCS antenna elevated a couple of meters.
Seppo June 28, 2012 at 4:17am

RFD900 Modems are now available for purchase from the RFDesign online store : http://store.rfdesign.com.au

End of last week we ran through SMT production in Melbourne, Australia and this week we have run through testing and finishing of the radios.

So far they have flown with a few open source autopilots, with nice range

RFDesign

RFDesign designs and manufactures the Antennas, RF Electronics and the RFD900 radio modem
Greg June 8, 2012 at 2:33am

Seppo,

I thought I would check in and see how your testing is going? Are you getting close to production units yet :-)
Jake Stew June 1, 2012 at 1:01am

That MAX2235 looks like a pretty decent PA. 47% efficiency isn't the best, but it seems like you just can't find everything you want in one PA chip anywhere.

Are there any heat issues with it? I'm guessing it just has thermal vias under it?
hamadivo May 29, 2012 at 5:00am

Hi all,

i have 2 DNT900 module for sale.Contact me if you are interested.

Thanks.
Nick Arsov May 29, 2012 at 12:16am

Hi Seppo,

Do you intend to manufacture RFDxxx for Europe....868MHz...433MHz..etc.?

Best regards

Nick
Jake Stew May 28, 2012 at 9:53pm

Nice work! The 3DR radios are decent, but they didn't really incorporate that many of the features I had initially planned when I proposed the idea of creating a Si1000 based telemetry radio. They chose to go with the HopeRF module instead of creating an original design or using the reference design. It's good see there's still some good engineers out there willing to do more than slap a module on a carrier board.

A few questions come to mind...

Have you done any tests to check your actual receive sensitivity? 3DR claims to have a sensitivity even higher than the HopeRF module they use, despite the fact that I pointed out how foolish and obviously false that claim is.

Which amplifier chip did you use (RMFD, Skyworks, Maxim, etc.)? Or did you use a discrete design?

Is there a passthrough? That is can you turn the amp on and off?

Can you vary the RF output by changing the Si1002 output? Or is the amp gain controllable in some way?

How much current does the unit draw at various output levels?

I see there seem to be at least 6 pins exposed. Have you thought about using your unit as a RX replacement? That is do you think you could output PWM or PPM or even some simple relay/GPIO control?

Sorry to hammer you with so many questions, but it looks like you've actually produced a unit very similar to the one I envisioned and suggested on this forum last September and I'm excited!
Seppo May 28, 2012 at 4:41am

Hi Greg,

The radio is a clean-sheet design. It is based on a Si1002 transceiver from SiLabs which allows a software solution called "SiK" to be used on it.

SiK is also used on the 3DR radios, so protocol, framing, hopping etc. is identical which allows them to talk to each other (900MHz versions only).

One thing that I needed was long range and diversity. Diversity being especially useful as it automatically chooses the best antenna for each packet it sends/receives. For UAV or mobile applications, having two antennas, one in each polarisation, reduces the chance of link loss significantly. I have not seen any ISM band radios to date that support diversity by default.
Greg May 28, 2012 at 4:14am

Seppo very nice product. I just started using the 3DR Hope-RF based Radios (915 MHz)and was looking to purchase an amplifier from Shireen to increase the range and here is the perfect soultion for me and in one module. When you say 100% compatible, is your RFD900 using the Hope RF module or some thing else?

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