Cool Pixhawk-compatible long-distance directional radio

Pharos matches a dynamic directional (beam shaping) radio on the air with another on the ground, with the two tracking each other for multi-mile range for video and telemetry. Coming to Kickstarter in 2-3 weeks. 

The Pharos is a newly-developed smart antenna. Unlike conventional omni-directional antennas that waste energy in all directions, the Pharos concentrates the available power where you need it most. Working in conjunction with the Pixhawk autopilot (a version with its own autopilot is being also developed), the antenna activates the side facing your UAV, boosting reception and range. A second Pharos can also be used on the aircraft, quadrocopter or UAV, keeping ground control in aim at all times.  The Pharos is also circular-polarized, granting immunity to polarization losses and multipathing signals, an optimum choice for challenging environments.

Air:

Ground:

Views: 4694

Comment by Monroe King on May 6, 2016 at 8:45pm

Hummm perhaps I misjudged at least for some applications?

Now it makes a little more sense. Perhaps I can do some testing?

Comment by Hugo Chamberland on May 7, 2016 at 10:45am

This is the pattern of a single Pharos elements.

This is an elements with typical pattern of an omni antenna (in red)

This is the total coverage of the Pharos.

-Hugo


Developer
Comment by Bill Bonney on May 7, 2016 at 12:41pm
How about the elevation beam. Since a dipole is spherical. Most directional beams have poor performance in elevation plane.
Comment by Monroe King on May 7, 2016 at 2:46pm

Nice Hugo, good come back. That's the kind of information we really need. Thanks!

Comment by MAGnet Systems on May 7, 2016 at 3:55pm

Let me also mention a specific set up that we have tried which gives optimal results on extending not only the video but the telemetry link as well through the Pharos antenna:

Connecting the Pharos antenna input to the Microhard 5.8GHz digital modem output will allow streaming both video and telemetry from the same unit. (a.k.a. a single radio and a single antenna is used on each side of the link).  These modems have 2 available serial ports at TTL levels and an IP port.

We use one serial port for the MAVLink telemetry just like using the standard telemetry radios and the spare one for additional serial devices (i.e. RTK GPS). We also use the modem’s IP port for streaming video. Here, you can directly plug an IP camera board i.e. a RasPi day or night camera or you can use a tiny analogue-to-IP video converter and plug any analogue camera without restrictions.  We use a low cost 38x38mm OEM converter board that works explicitly well.

Since these modems are bi-directional, we can both sent MAVLink commands to the drone and receive fast telemetry to the GS plus hi-res video. The available bandwidth is up to 12Mbps but in most cases we don’t exceed 1-1.5Mbps fact that allows the modems to retain a high Rx sensitivity.

The downside of the above set up is that these modems are pricey as their capabilities exceed the average use. But summing up the costs of telemetry radios, FPV radios, antennas, motorized tracking units, etc. the budgets required for the two different systems converge a lot, not to mention the reduced complexity, reduced weight, digital quality etc that the digital modems offer. More information and connection diagrams on the specific set up above you will find here, at the bottom of the page.

In any case, it is up to the users to decide which set up suits them best according to their needs and budget (purely hobby Vs more upscale) but the Pharos antenna will improve the 5.8 GHz link in all cases.  

 

Evangelos 

Comment by Monroe King on May 7, 2016 at 4:12pm

That radio is very interesting indeed.

Comment by Hugo Chamberland on May 8, 2016 at 12:33pm

This is the elevation plane of one pharos element.

One advantage of the crosshair type antenna is it's excellent axial ratio (circularity) which is maintained even at extreme beam angles. Unlike a helical, for example, that is only really circular within a 50-60 deg. beam. Observe the red pattern in the picture above that depict the cross polar component.

-Hugo

Comment by Art on May 9, 2016 at 5:13am

You increased complexity of the system for no quantifiable gain.  Since it is touted as a multi-mile range solution I assume that intent was to improve range of communications.  Well let's just try to use math instead of colorful superlatives to see if the goal can be achieved with this solution.


Free path loss for your system at 4 km  is (lets assume that you have your antenna at both ends and include gain of 10dBic of both antennas) - 99.75dB


Now let's look at any other currently used 900MHz telemetry link with two 2dB whip antennas at 4 km - 99.57dB

So I see no advantage to this solution at all.


You might get slightly better noise figure at the receiving end because of circular polarization but not by much unless you are flying in urban jungle and multi-path is an issue.  But then you are not really going for a long distance in the first place.  For normal operation (aircraft high in the sky base station antenna elevated) that shouldn't be an issue.

Comment by Fnoop on May 9, 2016 at 6:24am

Really cool idea!  Can it be used with 5.8ghz wifi, assuming the adapter has sma connector?

Can one end be something like an immersionrc rhcp mushroom or dish antenna?

Comment by Hugo Chamberland on May 9, 2016 at 8:43am

Yes, it have a SMA and can be used with any 5.8GHz Rf device be digital or analog.

The other end of the link can be anything, analog Vtx with RHCP omni or high gain dish.

The ultimate version of this antenna contain it's own microhard modem (1W Fcc compliant) that provide two serials and one IP link. A all-in-one solution for video/control/telemetry.

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