42 replies to this topic

[dankers]

As a lot of long time UAV people know, there is a real lack of a good telemetry radios around that will do what we need. Most people get by with Xbee modules and these work to an ok level but have limited range, limited bandwidth, are expensive and also need expensive breakout boards. Furthermore they are closed source and the most suitable Xbee radio for our needs is the 2.4Ghz Pro module, this of course clashes with 2.4Ghz systems used for Radio Control and although they can work together, it results in range reduction and lost packets / retransmits.

With all this in mind we needed a good alternative, while there are some other nice radio modules around, they are mainly too large, too heavy or far out of the price range of most people. So we did what all good engineering projects do, made our own; something perfect for UAV use, something with good range and a great balance of features Vs performance. Hence, the PipBee Pro was born.

The PipBee has a series of very exciting features, here are just some highlights:

• No breakout board needed, USB port and micro serial socket on board.
• Has the very powerful STM32 Microcontroller on board at 72Mhz.
• Open Source firmware licensed under the GPLv3.
• 250Kb/s data rate.
• API mode.
• AES encryption.
• Digital Spread Spectrum and Frequency hopping.
• Small, versatile footprint which is the same as OpenPilot AHRS & GPS, can be mounted in a stack on a Quad for example.
• Plug and play with the OP Cable set, OP will also power the board from this connector.
• Standard SMA antenna connector.
• When using with a PC, just a single USB cable is required, this will power the board as well as provide a USB to serial connection.
• Cross platform configuration tool - Mac, Linux & Windows.
• OpenPilot GCS support.
• Will utilise PiOS and other OpenPilot technologies.
• Fully certified radio and legal for license free operation in the global ISM bands.

The following frequencies will be available:

434Mhz - Worldwide

868Mhz - Europe

915Mhz - USA, Australia & Israel

Power output is 100mw.

I'm extremely excited about these and it has been hard keeping quiet, there is still much testing left to do and code to write, more information to come as things progress.

[Gary Mortimer]

I'll have 100mW at 434 please, that should punch a little further, best we get an antenna section running!

[dankers]

I agree!! 434Mhz is where it is at for me as well, I expect this to be a popular frequency and the PipBee Pro was originally designed as a 434Mhz radio, but because of the very flexible and cleaver design (by Pip hence the name), it was very simply to add the other two ISM bands. I also think 868Mhz is a major achievement as well as the Xbees in this range are simply a waste of time, their duty cycle is so low that they are not usable for anything but extremely low data rates. People in mainland Europe are then forced to use Xbees at 2.4Ghz which clashes with RC but also means they have much less range. For the non-radio guys, the lower the frequency the more range for the same power level.

[Scooter]

I hate to say it but 900MHz is not open spectrum in Israel. It's in use by the GSM900 band. That being said, there is a lot of under-the-radar (:-) usage by American phones and the like. Discrete usage seems to not arouse any trouble. But organized usage would be a problem.

[Scooter]

By the way, this definitely sounds like a huge win. I'm new to the hobby UAV scene, and I noticed pretty quickly that the radio solutions available even today pale in comparison to the Ricochet modems (1990s tech) which offer 900MHz 1W (!) output at a peak 256kbps bandwidth. This is seriously old, understood tech, but for some reason no one is offering reasonably-priced solutions yet. I happen to have a whole bunch of GS modems, and one GT, that I bought many years ago and this happens to be a perfect use for them. That being said, they are heavy, closed source, and long out of production, so they aren't appropriate for wide usage.

[dankers]

That's good to know about Israel, thank you. At one point this was allowed in Israel for sure, also in Australia we have 900Mhz for mobiles as well (Vodafone use it), the thing to watch for is that the PipBee device must accept interference from these licensed operators. The radio modules are certified for this so here they are legal, it might be worth checking but anyway there is 434Mhz anyway.

The Ricochet modems were awesome, I've linked offices together with them running NetWare back in the day, ok, I feel old now.

[Scooter]

Dankers, I could be wrong about the 900MHz status in Israel, as I never heard of it being open. Either way, I'm definitely interested in the 434MHz version.

One other thing. What is the RF device for the PipBee?

[Scooter]

Okay, I am happy to be wrong, according to this:

http://en.wikipedia.org/wiki/ISM_band

[dankers]

Makes sense. There has been a load of testing done with many RF vendors and a lot of literature from most of them states their modules in the 900Mhz ISM band is legal in Israel. Nice to know Wikipedia agrees as well.

[Gary Mortimer]

Remember that the World Radio Council meeting is this year I think and will discuss frequency allocation for UAS. For sure ISM will be fine but maybe they did not forsee lots of Aeronautical Mobile operation 30 years ago!

[Lew Payne]

Scooter, on 08 August 2010 - 05:49 PM, said:

By the way, this definitely sounds like a huge win. I'm new to the hobby UAV scene, and I noticed pretty quickly that the radio solutions available even today pale in comparison to the Ricochet modems (1990s tech) which offer 900MHz 1W (!) output at a peak 256kbps bandwidth. This is seriously old, understood tech, but for some reason no one is offering reasonably-priced solutions yet. I happen to have a whole bunch of GS modems, and one GT, that I bought many years ago and this happens to be a perfect use for them. That being said, they are heavy, closed source, and long out of production, so they aren't appropriate for wide usage.

Hello Scooter - Thanks for spoiling my day. Your mention of the Ricochet modems reminded me of what an ancient dinosaur I am. I lived in Silicon Valley when they were being rolled out, and the Ricochet modems (along with their AT-command compatible dial-out service) were pretty neat. I still have a pair of them stored in a box somewhere, as a testament to the era I grew up in.

There are many viable (and inexpensive) solutions to the wireless modem these days, suitable for UAV's. I maintain a list of them in my technical blog, which you're welcome to check out. In particular, look at the DNT-900 under "RF Transceivers." 900 MHz ISM band, FHSS technology, FSK modulation, .01 to 1.0 Watt, 1.2 to 460.8 kb/s, and very good (-108 dB/m @ 38.4 kbps) receiver sensitivity. Price... $69/each (less than the price of a Ricochet)!

de KA6RBJ

[Pip]

The older type RF modems most likely have better strong signal and adjacent channel signal handing properties than the all-in-one UHF chips (like the CC1100's etc) around today.

Keeping the on-board 100mw/1W 1.3GHz/2.4GHz/5.6GHz etc video transmitter energy out of the on-board data modem is the main problem I think that people will have.

I'm also not sure if the GPS receiver has a filter on the it's antenna to filter out any of the on-board transmitters.

I will be mounting the UHF 1/4wave data-modem aerial upside-down on the underneath of the quad to keep the radiation away from the GPS, and also mount the 2.4GHz video aerial upside-down as well underneath. This makes sense anyway to me as the UAV is most likely always above the ground station, so you want the communication antennas to have there radiation patterns biased towards the ground rather than biased skywards.

[Lew Payne]

Filter for GPS L1 1570 and for 2.4GHz Design and Measurements

Conclusion: "A 7 pole low-pass filter perform better then conventional readymade filters for this type of application! But this type of filter can not be used if the video transmitter is operating at 1Ghz, then the frequency spacing is too small."

Yes, I know... the above wording leaves a lot to be desired (from a technical perspective).

Some more cute-looking pics can be found here.

[dankers]

Lew Payne, on 09 August 2010 - 05:23 PM, said:

In particular, look at the DNT-900 under "RF Transceivers." 900 MHz ISM band, FHSS technology, FSK modulation, .01 to 1.0 Watt, 1.2 to 460.8 kb/s, and very good (-108 dB/m @ 38.4 kbps) receiver sensitivity. Price... $69/each (less than the price of a Ricochet)!

The DNT-900 are heavy buggers with their metal shielding and fairly large. Lew, you know OpenPilot, you know we evaluate everything, we did not select these units . Unlike some other projects that just slap shit on a board and throw it out of the door without testing, we spend a lot of effort and money on R&D to get the best solution, we take pride in what we do, a lot of pride. The PipBees will be awesome, they won't be released until they are, its that simple. The DNT-900s are also just the module, like the Xbees and friends they also need breakout boards of some type and this adds to the price and weight as well.

The specs you list are not right, for 500 kbps this unit has a max output of just 85 mW. You only get 1W at 200 kb/s which is slower than the PipBee and the big concern is that 1W is simply too powerful when mixed with everything else on a UAV. We did consider amplifying the PipBee to 1W and might still might as part of of our testing but it is a lot of RF power when mixed with everything else, there needs to be a balance between usability and hassle for users Vs range. Not sure we really need 40 miles to be honest

[Lew Payne]

dankers, on 09 August 2010 - 08:16 PM, said:

The DNT-900 are heavy buggers with their metal shielding and fairly large.

Yes, I figured form factor (and form - in terms of its metal RF shield) would nix it from being selected for OpenPilot. The pic shows the bare board, which may lead some to believe that's the entire form factor (somewhere on the pic page, it mentions "shown with RF shield removed" or such). For someone who's looking for a cheap and off-the-shelf solution, the DNT-900 is a formidable $69 (USD) performer. But again... if form factor and integration is a consideration (which for OP it is), then you can't beat a custom-designed solution.

dankers - Please help me figure out a way to mount my Henry 1K RF amplifier on a FunJet. I have already acquired the 400' (FAA/AMA ceiling) extension (mains) cord to power it.

[Lew Payne]

Pip, on 09 August 2010 - 07:12 PM, said:

I will be mounting the UHF 1/4 wave data-modem aerial upside-down on the underneath of the quad to keep the radiation away from the GPS, and also mount the 2.4GHz video aerial upside-down as well underneath. This makes sense anyway to me as the UAV is most likely always above the ground station, so you want the communication antennas to have there radiation patterns biased towards the ground rather than biased skywards.

pip, I'm curious about something... if you have the 2.4GHz video aerial mounted upside-down, with a ground plane (even if it just consists of several radials) between it and the GPS unit (with the GPS antenna sitting above, centered on the ground plane), how much signal separation does that give, in terms of increasing the front-back ratio for each respective antenna?

Does inverting the antennas, and separating them with a ground plane, afford better attenuation between them than opposite polarizations (horizontal/vertical)? Not that polarizing them is an option... but just from a strictly theoretical perspective.

[dankers]

You're going to need a bigger Funjet for that Henry 1K.

The shielding caught me out on the DNT-900, they don't make it clear at all. They would be suitable for very big UAVs only, 1.5M+ wing span stuff and they would be fine.

Lew Payne, on 09 August 2010 - 09:37 PM, said:

Yes, I figured form factor (and form - in terms of its metal RF shield) would nix it from being selected for OpenPilot. The pic shows the bare board, which may lead some to believe that's the entire form factor (somewhere on the pic page, it mentions "shown with RF shield removed" or such). For someone who's looking for a cheap and off-the-shelf solution, the DNT-900 is a formidable $69 (USD) performer. But again... if form factor and integration is a consideration (which for OP it is), then you can't beat a custom-designed solution.

dankers - Please help me figure out a way to mount my Henry 1K RF amplifier on a FunJet. I have already acquired the 400' (FAA/AMA ceiling) extension (mains) cord to power it.

[dankers]

A thing of beauty

[PeterG]

Does it use the 802.15.4 protocol?

[Pip]

PeterG, on 10 August 2010 - 08:00 AM, said:

Does it use the 802.15.4 protocol?

It doesn't use anything at the moment, I've not written any firmware for it as yet.

I will have to take a look at the 802.15.4 protocol to learn about it first. But to start with it will use it's own basic packet format (at least to get going).