Amazing FPV R/C flight over New York.

[flecom]

If you watch the interview video, this claims to have obtained 120 mile range for both control and video streams. That is the amazing thing.

I am sure that is LOS

[dnar]

I am sure that is LOS

Yep, I am sure too.

[buffo]

120 miles line of sight? Where on earth did they test that?

Using a simple LOS calculator, both the transmitter and the receiver would have to be 1800 ft above ground level in order to get an LOS distance of 120 miles. (Curvature of the earth and all that...)

Since I doubt that the guy running the transmitter was able to get that high (the tallest accessible rooftop in New York is well under 1000 ft), that would put the plane at over 3000 ft. And if he was standing on the ground, the plane would need to be at nearly 7000 ft!

Seems a bit far-fetched for an RC aircraft...

OK, maybe they went out to Kansas where it's nice and flat, but even so, they'd need to be way the hell up in the air. I'd like to know more about how they tested that range...

Adam

[dnar]

Not necessarily. Without knowing the frequencies I am only speculating, but the ionosphere could be a factor.

[buffo]

The frequencies that are authorized for RC vehicles are all in the VHF band or higher. The standard band for RC planes is at 72 Mhz. DSM and spread-spectrum radios are several orders of magnitude higher (UHF). In both cases, the waves will shoot straight through the ionosphere.

Adam

[mixedgas]

The ham radio record for tropospheric ducting is 1,675 miles at 10 Ghz.
Cape Verde Island to Portugal, and the direct path record is around a fifth of that. These records used one or two meter dishes at 10.

The 2.4 Ghz ham record is 145 miles. These are all done by mountain topping or ducting or refracting the signal off terrain. At 2.4 Ghz the required dish is huge.

You may not need more then 250 feet of terrain for a long ham microwave shot, but it sure helps. If you want a consistent shot, you get out Buffo's path calculator and follow it.

They also use a very narrow bandwidth for those records, for signal to noise reasons. Much narrower then RC needs. Basic RC is about 10 khz wide, and the new spread spectrum ones, much wider then that, probably a Meghertz or more.


I can get at 10 Ghz summer shot from Cleveland to Michigan or Cleveland to South Ontario, at lake level, a form of water vapor ducting but not consistently. Doing it at ground level, over land, no way, maybe once a year.

One thing with microwaves, water vapor and oxygen adsorption wreck havoc with your signals, depending on the band you use. That is why 2.4 Ghz or 5.6 ghz is used for WIFI, without big antennas with lots of gain, it cant get far because of water adsorption. Put a tree in the way and the signal is just gone. This allows for reuse close by, which is why 2.4 is used.


However when you need direct links, that are 100% reliable and do not suffer from weather fading, the system of choice aka AT&T or Sprint's old microwave scheme, is a 250 foot tower, a 30 max mile spacing, and a second set of dishes to pick up the fades from Fresnel zone effects and index of refraction effects, spaced at least 200 wavelengths down from the main dish.

So the idea of a 120 mile test happening once is not far fetched with large antennas, but the idea of a affordable wide band RC data link at a minimum of a few tens of kilohertz or more doing a consistent 120 miles is BS without really, really special skills, antennas,a tower and care. Certainly not with anything antenna wise that would fit on that tiny bird.

DNAR,

AS for HF, he'd have to use a military style NVIS* scheme for the controls, and that is not going to be reliable enough, nor would he get real time video back. With 0-30 Mhz HF AM or SSB, and the military 20-55 Mhz FM, you look up your distance on a chart and change frequency accordingly. So that is not that viable.

I'm with Buffo, it does not add up. I can easily see a GPS autopilot do it, but not a direct path RC.

*Near vertical incident Skywave.

Steve

[dnar]

Fair enough. It would be interesting to conact thre pilot and ask how he achieves such range.

[f22warzone]

I can go up to a mile LoS on my FPV platform, the radio is good for 2 miles while the 500mw video 900mhz feed is only good for about a mile before it starts cutting out ( have to do range test before attaching it to the bottom of the helo) All i have to do now is make the camera mout and i will have a said FPV platform, the video, rx, tx was only 100$ to.

[lasersbee]

I can go up to a mile LoS on my FPV platform, the radio is good for 2 miles while the 500mw video 900mhz feed is only good for about a mile before it starts cutting out ( have to do range test before attaching it to the bottom of the helo) All i have to do now is make the camera mout and i will have a said FPV platform, the video, rx, tx was only 100$ to.

I could use a link to where you got your equipment... I'll try something
new..

Jerry

[dave]

Very cool man!..