Espritmodel.com Telemetry Radio
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Old Feb 21, 2013, 12:45 PM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
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Actually, I think what I wanted to ask is are they "serial UART" ie, the same serial data interface as the XBees?

Jimmy
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Old Feb 21, 2013, 05:11 PM
Registered User
Australia, QLD, Brisbane
Joined Nov 2011
110 Posts
Hello Jt,
The RFD900s have a standard hardware serial port (UART) which is electrically the same as on XBees etc. -
It is a TTL level serial port, it can accept 3.3v, or 5v signals. If you want to connect to an RS232 port, you will need a level translator, which will convert the +/- ~9-~12v RS232 signal levels to +5, or +3.3v...
Hope it helps!
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Old Mar 01, 2013, 01:42 AM
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Australia, QLD, Logan
Joined Aug 2011
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Fyi: I've visited Seppo twice (at work), bought a fair bit of his gear and found him to be a pleasure to deal with. His service is efficient, he's very patient with my many questions, considerate of my requirements and reasonable with issues. And a thorough gentleman, to boot. M.02
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Old Mar 01, 2013, 07:05 AM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
We're going to start carrying the RFD900's as an option for our systems and I've also found the Seppo is very responsive to answering requests for assistance with his products. Really appreciate the support!

Jimmy
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Old Mar 10, 2013, 09:37 AM
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Reasonable noise level

Hi Seppos

I got my RDF900 few weeks ago and today I try a 2 KM flight at 200 meter ASL. The link is solid throughout the flight but upon check with Mission Planner graft log, the remnoise radio and rssiradio is almost touching. The remnoise level is about 100. I would like to know if the noise level is acceptable or I'll have to move around with the antenna.
The initial signal level is at about 220, the drop to 100 at the 2 KM turning point. The link drop may due to this is not a LOS flight. There is a hill about 80 meter high 500 meter in front of us.
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Old Mar 10, 2013, 10:00 AM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
I would bet that it's an LOS issue. 2 km at 200m can be challenging even on flat terrain. The further out you go, the higher you have to be.

Jimmy
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Old Mar 11, 2013, 06:47 AM
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Australia, QLD, Brisbane
Joined Nov 2011
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Hi Keeyen,
the remote noise level is quite high, so definitely relocating the antennas is worth looking into. Typical noise levels can get to 60 or so, depending on whats around. What was the localnoise level at? If you are able to fit the dipole antenna into the airframe, it is worth using it as it has it's own ground reference and will not couple as much noise through the feed coax. The hill will definitely reduce coverage as well..
Cheers,
Seppo

Quote:
Originally Posted by keeyen View Post
Hi Seppos

I got my RDF900 few weeks ago and today I try a 2 KM flight at 200 meter ASL. The link is solid throughout the flight but upon check with Mission Planner graft log, the remnoise radio and rssiradio is almost touching. The remnoise level is about 100. I would like to know if the noise level is acceptable or I'll have to move around with the antenna.
The initial signal level is at about 220, the drop to 100 at the 2 KM turning point. The link drop may due to this is not a LOS flight. There is a hill about 80 meter high 500 meter in front of us.
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Old Mar 11, 2013, 09:56 PM
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Thanks for the answer. I'm not quite sure about " fit the dipole antenna into the airframe " are you means fit the antenna directly into the radio modem without extension? I install both the monopole and dipole antenna into the modem. Is it better to use only one dipole ?
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Old Mar 11, 2013, 11:32 PM
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Australia, QLD, Brisbane
Joined Nov 2011
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Hi Keeyen,
I meant that if there is enough room in the airframe, to use a dipole is preferred if possible.
The monopole connected directly to the modem will utilise the modem and attached wiring as the antennas ground reference - this will couple more noise into the receiver, giving higher remnoise levels... It would be better in this case to use only one dipole in the airframe.
To get the best performance out of a monopole, a groundplane on the external surfaces of the airframe is needed with a bulkhead connector mounting the monopole externally.
Seppo-
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Old Mar 13, 2013, 03:36 PM
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Hi all,

Just wondering if anyone has had experience with this and the autoquad FC? Are there any issues? Has anyone managed to carry out a range test?

Also, mounting on a hexakopter frame what antenna's are recommended? I'm guessing two dipole 3db antennas facing down located on opposite arms would be ideal? Or is it better to have 1 dipole and 1 monopole located on opposite arms?

Cheers

James
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Old Mar 17, 2013, 03:40 PM
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Joined Mar 2013
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RFD900 max data throughput?

Hi all,

RFD900's max air data rate is given as 250kbit/s, but seeing that it's UART interface is max 115200 baud, I guess that the max data throughput becomes 115200 bit/s in any case. I know that 1 baud is not always = 1 bit but given no other information to go on, it would seem to be the case here, right?

Regardless of the above, would it be possible to operate 2x2 RFD900 on different freq's in parallel if one wanted more data thoughput?

Cheers,
C
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Old Mar 17, 2013, 11:36 PM
Registered User
Australia, QLD, Brisbane
Joined Nov 2011
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HI Copenhagen,
Yes, we have successfully run 2 modems in one air platform - There was a notable increase in sporadic noise levels when the channels clashed from time to time, but maintained link well at around 7km. The best way to test it is to try it in your application - we were sending Mavlink telemetry data so the link was not heavily loaded.
Hope it helps,
Seppo..
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Old Mar 18, 2013, 03:29 PM
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RFD900 max data throughput, 2x2 RFD900

Hi Seppo,

Thanks for the info! A 2x2 setup could be a useful option then.

Regarding the max data throughput, is it that 250kbit/s is a theoretical limit of the si1000 tranceiver while the uart 115200 baud is closer to the practial max transfer rates, given various losses? Or can true 250 kbit/s be realized under optimal conditions (modest range, good antennas, LOS etc) if e.g. the uart is disabled and flow-control is done by e.g. a external embedded computer connected to the RFD900? Or even if just bit-banged, if assuming optimal RF conditions?

Cheers,
C
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Old Mar 25, 2013, 09:55 AM
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Perth, Western Australia
Joined Dec 2005
327 Posts
Seppos.
Any update on the RCLink?
Regards,
Nick
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Old Mar 27, 2013, 07:40 PM
Registered User
Australia, QLD, Brisbane
Joined Nov 2011
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Hi Copenhagen,
The 250kbit/s is the maximum supported air data rate, and 115200 is the maximum supported serial interface rate. Going extreme, it may be possible to feed in more data via other ports and get that across the air at 250k. There is a slight amount of packet overhead, at an estimate around 10-15%, so around 200kbit/s may be an upper limit. Not exactly sure as haven't looked into it for a while.
Cheers!, Seppo

Quote:
Originally Posted by Copenhagen View Post
Hi Seppo,

Thanks for the info! A 2x2 setup could be a useful option then.

Regarding the max data throughput, is it that 250kbit/s is a theoretical limit of the si1000 tranceiver while the uart 115200 baud is closer to the practial max transfer rates, given various losses? Or can true 250 kbit/s be realized under optimal conditions (modest range, good antennas, LOS etc) if e.g. the uart is disabled and flow-control is done by e.g. a external embedded computer connected to the RFD900? Or even if just bit-banged, if assuming optimal RF conditions?

Cheers,
C
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