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Old Sep 11, 2014, 05:10 AM
A man with too many toys
United States
Joined Feb 2001
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Why is the RFD900u not sold in the US store? Is there a US certification problem?


I was thinking of a RFD900 ground station and RFD900u in the air to save weight and power. Will that combo work ok?


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Old Sep 11, 2014, 05:23 AM
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Australia, QLD, Brisbane
Joined Nov 2011
116 Posts
No reason apart from Jeff at Event38 hasn't ordered any to sell there!
Will see if he wants to buy some to sell there-

The RFD900 on the ground and RFD900u in the air works really well as a combo-
We will have some more 900u's in stock next week.
Cheers,
Seppo
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Old Sep 11, 2014, 10:57 AM
A man with too many toys
United States
Joined Feb 2001
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Ground Station Antennas

I just got my first RDF900 and was reading the instructions. Itís a little confusing about antennas. How are most of you arranging your two ground station Half Wave Dipole Antenna?


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Old Sep 11, 2014, 05:02 PM
A man with too many toys
United States
Joined Feb 2001
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RFD900u

Why did they eliminate ECC?

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Old Sep 11, 2014, 07:39 PM
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Australia, QLD, Brisbane
Joined Nov 2011
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Hi RC Man,

For the ground station antennas, a good configuration with 2 dipoles is to have one vertical, and one horizontal. This will give the best option for diversity with those.
If you have other antennas available, Yagis, Collinear Dipoles, etc, there are more options which can be customised, eg. pattern diversity, polarisation diversity and spatial diversity.

ECC was taken out in the current R9u tree due to memory map pain. It is planned to get it back in there at some point when there is more time available. The memory architecture on the 8051 is quite messy, it uses a banking system which we have working OK, but, in terms of efficient placement of code, the build system still has scope for improvement.

The source code is available online so any contributions from the community would be welcomed!
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Old Sep 12, 2014, 07:11 AM
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United States, CA, Los Angeles
Joined Nov 2010
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Quote:
Originally Posted by RC Man View Post
I just got my first RDF900 and was reading the instructions. Itís a little confusing about antennas. How are most of you arranging your two ground station Half Wave Dipole Antenna?


I wouldn't worry it too much unless you are going really long distances, like over 6 miles. I set mine with a 20-30 degree V and 10 degrees forward to backward. It's called the drunken rabbit ear style. Using the original RFD900 Ground and a 3DR Airborne, I still get 95 RSSI at 5 miles on the Ground. The air is not quite so good but your down link is usually the priority unless you flying with Joysticks and a computer.
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Old Sep 12, 2014, 07:21 AM
A man with too many toys
United States
Joined Feb 2001
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I was wondering if there is any difference in performance between V and one vertical and one horizontal. I will try it both ways and see if I get any RSSI diference.


I was looking at my APM telemetry log and the rssi in not 0 to 100%. I recorded between 80 and 170 on my first mission. Does anyone know the conversion factor?


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Old Sep 12, 2014, 10:16 AM
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Hi Seppos,

Any news on RCLink? Is it something you are still planning to offer at some point, or is it off the table?
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Old Sep 12, 2014, 11:52 AM
A man with too many toys
United States
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Originally Posted by Seppos View Post
Hello All! -
Thankyou for patiently waiting for updates on the RCLink addition to the RFD900 - it has been squeezed between projects and is very much under active development.

It was test flown on an AXN clouds in terribly windy weather a week ago and it flew OK - there are improvements we need to reduce latency. These are related to the RFD900 firmware at the moment - one thing that is under consideration is a low latency mode on the radios where they are optimised for low delay.
The delay through the link has been measures at 4 to 100ms -- 100ms is a bit slow for where it needs to be I feel, so it's under the oscilloscope to understand the delay trough the chain to reduce it as much as possible.

Interface wise, we did find some intereting things - related to how different receivers behave.. Currently we have been testing on Turnigy T9x and FRsky D8RII's. The input stage on the RCLink board is using the TXB0108 level translator which needed some tuning of thresholds to get reliable bidirectional servo PWM to happen. The next revision of boards will support this..

At the moment we have 12 PWM channels and one PPM channel.
There is also a TTL level serial port which is intended for telemetry link transfer across the RC link at the same time - this has not been implemented yet.
Also is 6 general purpose analog inputs which can be used for things like voltage monitoring, or any other kind of analog sensor.

We're using an STM32 arm microcontroller which has heaps of processing power to do almost anything we can think of at the moment. It is field upgradeable.

The dimensions are: 46.5 x 69.5mm, weight is 21.0grams with all the headers loaded.

Below is a picture of the flight test setup with modems and FRSky receiver.

Planning on releasing an updated PCB shortly with the IO fixed up and any other really cool features you guys/ladies can think of! If there are any specs or things that we should try to aim for, let me know !

Will it work with my Futaba 14SG on the ground and Pixhawk in the air?

Will there be a way to still have mavlink data telemetered to my ground station?

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