RFD900, RFD900+ - New long range radio modem

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

 

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sarkis,

A default key is set but obviously this is not very secure.

To change it you must set both ends with a new key that is the same.

Encryption is 128 bit or 16 bytes of hex data (32 nibbles of ascii hex characters)

The command is

AT@E=0123456789ABCDEF0123456789ABCDEF

change the string to any 32 hex characters (0-9,A-F) of your choice.

You must set all 32 characters. you can also set the remote end via RT instead of AT ( and don't forget to save AT&W)

make sure to set remote end first and reboot before doing local end or you will lose the link.

reset local end and check that you have connection again.

If you lose link set each one locally to the same key and try again.

i.e.

RT&E=0123456789ABCDEF0123456789ABCDEF

RT&W

RTZ

AT&E=0123456789ABCDEF0123456789ABCDEF

AT&W

ATZ

please assign your own unique KEY for security purposes.

Kent

ok, thank you

All in the know about RFD900 radios with Mavlink based telem data.

So believe it or not I'm having some range issues with my RFD900+ radios.  I keep reading and reading and hearing about how folks are getting 10km or 15km or more with the 30dBm setting and 64kbps bandwidth, but I'm getting ~1000ft!  No problems actually connecting, just really short range before degradation, details on setup below.  I'm putting ample power into both RFDs so I just can't figure out what the problem is.  Wondering if anyone has experienced something similar or maybe I just have defective radios?

I got my antenna tracker up and working with a 900MHz biquad attached to the rfd900+ but my telemetry link is marginal at best even at 1000ft away.  My tracker actually stops pointing due to data loss at anything more than that.  Any thoughts?  I have quarter wave dipoles on the "tx" end and on the "rx" end I've got my tracker with one biquad and one larger whip.  I'm only running the radios at 20dBm power output (default) but I should still get much further than 1000ft!  I put tx and rx in quotes since the link is obviously bidirectional.  Here's a couple photos of my setup.  Any help would be greatly appreciated. 

What is the signal quality if you check with MP or radio tools ?

In MP the signal quality drops to below 40% at 1000ft from home.  :(

Jeremy,

I can't see the photos you added.

From your description I assume you have something moving your antennae on the air side.

Is it both or just one antenna?

Might be best to go back to basics to find the problem.

Install standard antennae on the air side without position control.

Set power to 30 dBm (both ends). i.e. a normal set-up.

Check how this performs. 

Also send though a log of both your radio's config (ATI5).

If this test works then there is a problem with your controlled antennae somewhere.

If not then need to check anything else non standard ( antennae, and fitted securely).

Let us know how you go.

@Kent and @Paul thank you for the reply.  

Here's a link to the photos so you can see exactly what I'm talking about.  It has all my ATI5 params posted there as well.  BTW, the air side antennae are NOT pointing, simply using some quarter wave dipole omnis.  However, even using the 20dBm settings I should be getting more than 1000ft range before my signal quality degrades below 40%!  I'll have to try some of the tests you mention when I get some more free time this weekend.

http://imgur.com/a/56EfW

Also here's a video of my previous test that was obviously pretty close in range so you can see the tracker actually working.  Now to sort out that pesky telemetry signal problem.  

https://youtu.be/xzkEgagkWFE

Hi Jeremy,

Following on from Paul, if you check the signal quality in mission planner in the tuning page.  RSSI, Remote RSSI, Noise and Remote Noise are the parameters of most interest.

Generally noise is around 40-60 counts, and when both radios are set to 20dBm, in reasonalble (say 0.5m) away from each other, with dipoles, or monopoles, you should see around 205 to 217 on both modems for RSSI.

If both modems are showing similar values, then the hardware is OK.

If one is showing something significantly less, say, 150 to 180, while the other is at 217, then there is a modem issue, which we will sort out for you.

The biquad looks pretty nice, It will be interesting to hear how that works on the tracker..

On the copter side, to get the best results there, it is better to use a dipole (a little big I know), or, a flex 1 antenna on a plastic strip.  The monopole antennas, both straight and 90 deg versions are designed to work with a ground plane.

When mounted straight onto the modem, the performance is degraded, but, certainly not to the level you are seeing now.

With best regards,

Seppo

Seppo-

I'm also running into range issues with two RFD900x's purchased from Aero Systems West, but I think my issue is related to noise.  I'm running at txpower=20 on both sides of the link, and I get the following from an ATI7:

L/R RSSI: 238/238  L/R noise: 106/101 pkts: 189  txe=0 rxe=13 stx=0 srx=0 ecc=0/0 temp=28 dco=0

I see similar results (noise >90 anyway) both indoor and outdoor, and in the same location a 3DR radio will report noise of 30-60.  The radios are running:

ATI
RFD SiK 2.53 on RFD900xR1.1
RTI
RFD SiK 2.53 on RFD900xR1.1

Thanks in advance,

-Allan

I should mention as well that a spectrum analyzer I have is indicating a noise floor of -105dB in the 915-928mhz range, which is pretty close to what the 3DR is reporting.

Allan Matthew said:

Seppo-

I'm also running into range issues with two RFD900x's purchased from Aero Systems West, but I think my issue is related to noise.  I'm running at txpower=20 on both sides of the link, and I get the following from an ATI7:

L/R RSSI: 238/238  L/R noise: 106/101 pkts: 189  txe=0 rxe=13 stx=0 srx=0 ecc=0/0 temp=28 dco=0

I see similar results (noise >90 anyway) both indoor and outdoor, and in the same location a 3DR radio will report noise of 30-60.  The radios are running:

ATI
RFD SiK 2.53 on RFD900xR1.1
RTI
RFD SiK 2.53 on RFD900xR1.1

Thanks in advance,

-Allan

Seppo, 

Thank you very much for your reply.  I finally found some time to run this test, which I did in my enclosed garage here in San Diego, with no more than about 1m distance between the vehicle and antenna tracker.  Here's a quick pic of the plots, but to summarize, both noise and remnoise are running right around 50 counts and rssi and remrssi are steady (and nearly right on top of each other) at 190 counts.  Both my radios are running RFD SiK 1.12.  My apologies for not having a  spectrum analyzer laying around, but I could probably borrow one if that was necessary for this troubleshooting.  

I'd love to try a flex 1 antenna on the plastic strip... I'll tell you what, if we sort this range issue out I'll buy 2!  

The only thing that comes to mind to do next is crank up the power to 1W and see what kind of range I get from that, but really thought I'm about certain that isn't going to solve anything given I can only get 1000ft without quality issues.  Any other ideas to try Seppo?  I think given the range that others are reporting this is a bizarre problem.  Its not as if I have an issue connecting in the first place... Everything works EXCEPT the range.  Anyhow thanks all for the responses, pretty anxious to fly more than 1000ft!

Jeremy



Seppo said:

Hi Jeremy,

Following on from Paul, if you check the signal quality in mission planner in the tuning page.  RSSI, Remote RSSI, Noise and Remote Noise are the parameters of most interest.

Generally noise is around 40-60 counts, and when both radios are set to 20dBm, in reasonalble (say 0.5m) away from each other, with dipoles, or monopoles, you should see around 205 to 217 on both modems for RSSI.

If both modems are showing similar values, then the hardware is OK.

If one is showing something significantly less, say, 150 to 180, while the other is at 217, then there is a modem issue, which we will sort out for you.

The biquad looks pretty nice, It will be interesting to hear how that works on the tracker..

On the copter side, to get the best results there, it is better to use a dipole (a little big I know), or, a flex 1 antenna on a plastic strip.  The monopole antennas, both straight and 90 deg versions are designed to work with a ground plane.

When mounted straight onto the modem, the performance is degraded, but, certainly not to the level you are seeing now.

With best regards,

Seppo

Additionally, here's what Mission Planner spit out for my settings for the ground side.  Sort of a duplicate of what I previously posted, but there are a few more details here:

L/R RSSI: 204/205  L/R noise: 54/46 pkts: 838  txe=0 rxe=3 stx=0 srx=31989 ecc=0/0 temp=-270 dco=0 pwr=20

See the image link above for more a screenshot.

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