Omni 3+ Mile FPV Quadcopter System
I would like to present an FPV base system optimized for Quadcopters that I have been working on for several months. The system uses standard off the shelf components. The key characteristics are:
1) Omin coverage range >3 miles when flying at High Altitudes. No antenna tracking.
2) Non line of sight Landing coverage (0.5 meter) up to 1 mile.
3) On screen RSSI for FPV Video RX levels (both channels of diversity).
4) On screen RSSI for Futaba FASST control system.
5) Indoor base station using outside antennas with Omni coverage.
Unlike gliders and airplanes, most Quadcopters do not have the speed or flying time to go great distances. They do have the ability to hover close to the ground providing unique video and photography opportunities. The low altitude, often with non line of sight conditions, presents a control and video signal challenge unlike the high flying planes.
Although an amateur radio license is required for my particular implementation, elements of the system (like the RSSI for Video & FASST) could be useful in other FPV systems. Here is an example of a Quadcopter 1.4 miles away being controlled from inside my home via video on a large screen TV:
Note the two bar graph in the lower left corner of the FPV video. That is showing the signal level in dB for the two diversity receivers. The scale is calibrated such that that a signal just above the 0 level mark is still flyable. You can see that at 1.4 miles there is at least 12 dB of margin. (I am VERY conservative in my calculations).
During the development of this system I made extensive use of a Longley Rice modeling program to predict the control and video range for my local area. Here is an example showing the expected coverage for Quadcopter landings in my area:
Of course the high altitude coverage is MUCH wider:
Since all the details of the system is too much for one post, I'm going break it into multiple posts with an index link from here:
- Futaba FASST TX modification for Driving 2 Watt LCOM amplifier
- Futaba FASST RX modification for RSSI
- CPOD Antenna First Tests
- CPOD Radiation Plots
- Demostration of -95 dBm Video Signal
- Demonstration of Preamp for -99 dBm Potential
- 1.2 Ghz RX modification for RSSI
- Dual Video Receiver RSSI on OSD
- Using Longley Rice Model to Predict Range for Your System
- Collinear Antenna System
- The Ultimate Future FPV Video System: DVB-T (COFDM)
The above Index will allow thread discussions while maintaining a direct link to the primary information posts.
Bear with me since this might take a while to complete. I also expect some evolution of the design, especially with the antenna and multipath mitigation solutions.
Last edited by Old Man Mike; Dec 29, 2010 at 12:51 AM.
Futaba FASST TX modification for Driving 2 Watt LCOM amplifier
This modification is rather simple. After removing the battery and back cover, a cable assembly is used to provide an external connector (Gold RP-SMA on top of TX) to drive a 2 Watt amplifier:
The original U.FL cable from the mounted antenna is just rolled up on the left side in case I ever want to return to the standard configuration.
I used this U.FL to RP-SMA connector assembly so that a standard RP-SMA rubber duck could be used when not using the amplifier:
A cable with a Male RP-SMA and N Male connector is use to interface the 2 Watt amp.
Here is the 2 Watt amp I am using:
Now some may ask why have the 2 Watt amp when the standard system can do almost two miles. The reason is that 2.4 Ghz is easily attenuated by trees and the objective is to have control for low hovering even when there is non line of sight. My measurements show a reduction of 17 dB when there is 150 feet of trees blocking the signal and over 30 dB for 500 feet of trees! Here is an example of a test where the quad was mounted to an ATV and a run was made covering areas of dense tree blockages (colored yellow):
The Red area shows where the standard 100mw FASST signal dropped out. Area 1 and 3 had 300 to 500 feet of tree blockage. Area 4 had blockage by a barn and some trees. The same test run with 2 Watt amp had no dropouts anywhere.
I'm using a 6 dBi Collinear antenna from LCOM currently mounted at 6 meters just above my roof:
The 6 dBi antenna is about the maximum gain omni that can be used before the higher nulls become a problem for high altitude flights close to home. This antenna will eventually be mounted up 20 meters on my tower to provide even deeper coverage into wooded areas.
Thanks Jack, Rusty, Jesolins, Frederic, Tony and OMD for the nice comments!
Tell me what additional info you need about the FASST amp and I will try to clarify my post.
Also, Simon posted this in another thread:
This is the quad:
Total cost of everything shown above is around $1900.
Here are some notes about the specific items on the quad:
1) KPC-VBN190NH FPV camera - This bullet type camera seems is a bit clearer with a higher line count than the previous KX-171 camera. I use a f2.97 mm lens instead of the stock 3.6 mm.
2) Eagle Tree OSD system provides the Voltage, Current and GPS information overlay for FPV flying. This is a very light weight system compared to other OSD systems I have tried.
3) Range Video 900 Mhz, 500 mw FPV transmitter - Works well as long as you have a good antenna matched to the TX frequency. Now using 1.2 Ghz Transmitter
4) OMM Vertical is my light weight dipole antenna design which replaced the poorly performing vertical that came with the transmitter.
5) Loc8tor Tags - I use two just in case one breaks during a crash since the Loc8tor is critical to finding a lost quad. Typical detection range is around 500 feet.
6) FASST 2.4 Ghz Futaba Receiver - No doubt in my mind that Fubaba has the best designed Spread Spectrum system for RC. (I use to design spread system radios for the military). I designed the OMM converter to provide a very high precision (no jitter) serial interface used with most of the quad controllers.
7) BL Controller 1.2 - The original controllers were produced with a lower than expected current limit. They were intended to have a 12+ current limit before foldback protection started. Instead, they typically are below 10 amps. I used a parallel shunt to increase the limit to aprox 14 amps.
8) OMM Foam Camera Mount with FX-35 HD Camera - Here is the link showing how it works:
9) Turnigy 2213/22 motors mounted with Brashley grommets - These motors are rated #3 as evaluated in the test platform here:
Now using 2217/20 motors.
10) EPP1045 Prop - A favorite of many quad builders. Now using APC1047 props because of inflight failures of the the EPP1045 props.
11) MK ME Flight Controller - NGhobbies is a great source for this and other MK parts.
12) 4900 mAh Rhino Battery - Great battery which provides 12+ mins of flight time for the 60 ounces system.
13) Rusty Frame - Built like a battleship. Rusty's frame design really protects the most expensive components. The repair cost for that crash video I just posted was under $30. The three CF legs helps to offset the extra rear weight from the FPV camera and also allows a clear forward view for the HD camera.
I'm using 1/2 inch Andrews Heliax for the 2.4 Ghz FASST and 1/4 inch Andrews Heliax for the 1280 Mhz receive. These are fairly short runs of 50 feet to my roof top. Eventually I will be mounting antennas on my tower at 66 feet and will be using 7/8 inch Andrews Heliax for most of those runs.
Try doing this with a fix wing (apologies to my quad friends for the repeat post):
By the way, here is the outlined area in the FPV view which corresponds to the HD camera view:
Last edited by Old Man Mike; Nov 25, 2009 at 06:37 PM.
Thanks for taking the time for writing all that up! I was wondering if you were using an additional amp for such long cable runs? Not necessary it appears? What's up with the DTV mods?? Whenever you catch your breath from all your detailed writing of course...
Again, thanks for this tutorial (and all your others, too). It is fantastic!
I recall reading your excellent thread on buiding a notch filter to lessen GPS interference from the 900MHz Tx a while back and I'm curious - does the TXF-900 low pass filter accomplish the same thing?
Also, what are you using now that you've switched to 1.2GHz? Or, is it not a problem up there.
Finally, I have a 2nd Class FCC license from back in the day, but I don't think it's relevant today. Will a Technician Class license make me legal to use your setup?
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