1.3GHz FPV with High-Gain Helical Antenna

We usually look for a high or open spot to stand when flying long-range FPV to avoid our signal being attenuated by obstacles. This allows us several kilometers of range in the countryside without needing a directional (high gain) antenna. Sometimes you might not have such an ideal spot to fly from though, so it helps to use an antenna with a narrow beam to focus that weak signal.

We attached a handle, video receiver, and battery to the back of this Circular Wireless helical antenna so it could be held by one person and manually pointed toward the copter, while the other person flies FPV:

Circular Wireless Heliaxial 1.3GHz antenna with video receiver, battery, and handle mounted to back

On the video tx side we used the Circular Wireless Skew Planar Wheel. In our long-range mountain flying test, we started from a low point near the base of the valley, in a location with obstacles such as trees and buildings. We were still able to fly over 2.0 km away with a clear video signal.

Flew FPV in the mountains of Changhua to a peak 2.0 km away.

A drawback of the Heliaxial is that it is bulky, needs to be transported carefully to avoid breakage, and is probably too heavy to be mounted to most antenna trackers.

Fortunately, Circular Wireless has come out with a new Circularly Polarized 1.3GHz Patch Antenna that should be much more convenient. We plan to test it out on a flight soon!

1.4 km away, FPV Touch-and-Go behind Hill in Rain...

Flew in the rain 1.4 km away over a hill and did an FPV touch-and-go... followed by a 2-km SplineNav scenic flight back, and near electrocution of the copter (oops!)—and all of that in one single epic flight!

It's very hard to get good FPV range flying near the city: even with 1.3GHz and a high-gain (directional) antenna on the receiver, we only get about 1 km range hugging the terrain (much longer range is available flying high, but that doesn't make for as interesting videos).

So we headed out to the countryside to find radio quiet, and left the bulky high-gain antenna at home. With just a Circular Wireless SPW12 on both tx and rx, we were able to fly 1.4 km away, duck behind a hill, make a touch-and-go, and still get perfect video back the whole time.

Unfortunately the video still doesn't work well flying behind broad-leaf trees, even at much shorter ranges. Evergreen needle trees don't seem to be a problem though, perhaps due to their lower moisture content. We're now using a Lawmate 1000mA 1.3 GHz transmitter, which seems to work a lot better than the ReadyMadeRC tx, and is much lighter. We use RangeLink UHF for radio control, which seems to be pretty much invincible at any distance.

After doing the the touch-and-go on the grassy hill 1.4 km away, we engaged SplineNav and did a 2-km scenic flight back on autopilot. The rain was really picking up, and moisture got into the gimbal electronics, which made the GoPro twitch wildly from time to time, but otherwise the water didn't cause any harm.

Note the temple with the four characters 周氏宗祠 we fly over at 5:18. That's where my wife attended elementary school, long since abandoned and with trees growing up inside it.

The change in weather on the flight back seems to have affected the barometer, because where SplineNav was supposed to have gone under that last power line, it went straight through inside. Really amazing that it made it through that narrow gap with no damage other than a split prop tip. These high-voltage wires are bare of insulation and carrying the power for the whole village. Fortunately the electricity didn't arc across right through the aluminum arms of the copter!

First Flight with GoPro Hero 3+ Black

The colors are quite drab and dreary in the mountains over the winter, and filming with the GoPro Hero 3 Silver just makes the colors even more washed out. So we swapped it out for the GoPro Hero 3+ Black, hoping to get some more vibrant, true-to-life color in our videos.

This was literally our first ever flight with this brand-new GoPro, so I was flying conservatively, not wanting to make a mistake that would result in lens scratches on the new camera, or worse. So sorry I didn't get in closer to that massive ridge of granite going up the mountainside. Maybe next time!

The winds were very high through this valley today, the GoPro was in Narrow FOV mode (1080p @ 60 FPS), and the gimbal only stabilizes pitch and roll, so those factors combined to create a whole lot of shakiness in the yaw axis. So although we were very impressed by the image quality in Narrow mode, it looks like for future flights we'll want to stick to Medium FOV. That is until we can get a 3-axis gimbal for our GoPro.

The colors certainly came out a lot better than with the old GoPro, but since there was so much haze and leafless or frostbitten vegetation, the video still came out looking fairly dreary and lacking in color. Good thing Spring is almost here!

WIN a FREE HoverThings Flip FPV Frame with a $136.95 Retail Value

Starting Wednesday, January 22, 2014 and ending Saturday, February 1, 2014 (23:59 PST), MavBot is running a Facebook Page Promotion 'WIN a FREE HoverThings Flip FPV Frame with a $136.95 Retail Value' at http://bit.ly/1f7sRKz . This page contains this Promotion's Official Rules.

'WIN a FREE HoverThings Flip FPV Frame with a $136.95 Retail Value' Sweepstakes - OFFICIAL RULES

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SWEEPSTAKES DESCRIPTION

Mavbot is giving away a FREE HoverThings Flip FPV Frame with a $136.95 Retail Value: a frame designed with TWO things in mind: strength and simplicity. The "FLIP FPV" is incredibly stiff and light, yet STRONG. The arms do not twist like cheap plastic arms, and they do not bend like expensive aluminum arms. It includes "snap-on" landing gear that can be installed and removed in seconds.

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1.3 GHz FPV Testing

Although our 5.8 GHz FPV setup works fairly well, I would prefer a video system that doesn't get all scrambled just flying behind a few trees, and that has much better range than just 2 km.

I thought we could do better with 1.3 GHz, so we've been experimenting with that. The first major test was this flight a bit over 2 km up a mountain valley near Baiguo.

1.3 GHz FPV Equipment used:

2x Circular Wireless 1.3 GHz SPW12 Skew Planar Wheel antennas
ReadyMadeRC 800mW 1300MHz Transmitter (2-channel US-legal version)
ReadyMadeRC 900MHz-1.3Ghz Receiver SAW w/1258 Custom RMRC Version 3
ReadyMadeRC Low Pass Filter for 1.3GHz Antennas (on vtx to help prevent GPS dropout)

Unfortunately, my tests so far have shown that the range is about the same as we used to get with 5.8 GHz and the Circular Wireless 5.8 GHz helical antenna. Of course it is nice to no longer have to keep turning your head to track the aircraft, but I'd prefer a solution where I can fly behind a few trees without losing most of the video signal. And in terms of that, 1.3 GHz FPV seems to be performing even more poorly than 5.8 GHz.  At least with 5.8 GHz I could fly behind maybe 6 to 10 trees before losing the signal completely. But in recent 1.3 GHz tests I lose the signal through just a couple of the same trees, and get glitches in the video just flying behind a single tree only 50 meters away!

So what's going on here that 1.3 GHz seems to have such poor tree penetrating power compared to 5.8, when supposedly it should actually be better? Interestingly, I've noticed the 1.3 GHz does penetrate concrete walls and rocks quite well, in fact much better than 5.8 GHz! So it's only trees in particular that seem to not like 1.3 GHz and prefer 5.8 GHz instead!

So if I want to reach my goal of flying FPV through trees with good video, maybe I'll need to try a high-gain antenna and an antenna tracker with 1.3 GHz, or perhaps move to 900 MHz video.

FPV Camera Wiring and Power Filtering

Here's a cable we made for our SecurityCamera2000 CMQ1993X FPV Camera (also works with the PZ0420). This cable powers the camera from a 3S LiPo battery, filters the power with a capacitor, diode, and ferrite choke, and sends signal and power to your OSD or Video Tx.

Make sure to get the wiring connections right: capacitors and diodes are polar devices. Also, they are heat sensitive, so make your solder joints quickly, before the devices have time to get super hot. Cover all solder joints and exposed wires with heat shrink to avoid a short that could shut down your whole aircraft and make it fall out of the sky, or even start a battery fire! Note also that power thru the diode in this circuit is only powering the camera; the diode should not be powering anything else besides the camera, as it may overheat and burn out.

1. Batt power (red) to positive (no white stripe) side of diode.
2. Negative (white stripe) side of diode to Positive (no white stripe) side of capacitor.
2. Negative (white stripe) side of capacitor to Batt GND.
3. Camera power (red) to Positive side of capacitor.
4. Camera GND (black) to Negative side of capacitor.
5. Camera signal (yellow) to OSD or Video Tx.
6. GND (black) from Negative side of capacitor to OSD or Video Tx GND reference (important: this wire runs straight to the OSD or Video Tx; don't use a ground reference coming via some other indirect connection that will result in a corrupted video image).

The resulting circuit is the same as the power filter for the camera in the project described here: http://www.rcmodelreviews.com/fpvbackpack02.shtml

And in the schematic at http://www.rcmodelreviews.com/filestore/Schematic.pdf, the upper left hand portion is this exact same circuit, with the capacitor and diode filtering the power for the camera.

Longer Range FPV for Cheap

I've been experimenting with ways to improve FPV range inexpensively, and here's what I've come up with:

1. I replaced the 5.8 GHz clover leaf antenna on my FatShark goggles with a helical antenna (and learned to use my own head as an antenna tracker).

2. I boosted my 2.4 GHz radio control signal with a 2-Watt WiFi booster.

The Antenna

I used this 7-turn Right Hand Circular Polarized (RHCP) helical antenna from BEVRC. It's cheap (only about $16) and has a 10 dB gain. I found this works better than using a patch antenna because interference from reflected signal is less of a problem. Make sure the direction of polarization matches that of the cloverleaf antenna on your aircraft.

Cheap 5.8 GHz RHCP 7-turn helical antenna from BEVRC

This antenna gives excellent range as long as I point it directly at the aircraft and it has line-of-sight. Reception through trees is still quite poor. It takes some practice to get used to pointing your head at the aircraft while flying FPV, but soon it becomes second nature.

WiFi Signal Booster

This cheap 2-Watt WiFi signal booster works with any 2.4 GHz radio, just connect it between tx module and antenna with the included coax cable.

Cheap 2-Watt WiFi Signal Booster

The WiFi signal booster came with a wall adapter for power. I cut the output cord off the wall adapter and soldered it to the outputs of a SkyRC 10-Amp BEC, which in turn is powered from the 3S transmitter LiPo. I installed the signal booster and BEC to the back of my FlySky TH9X radio using zip ties:

WiFi signal booster and BEC installed on TH9X radio

Range Test

In order to test the FPV range, I took a flight up in the mountains. The quadcopter got 2.3 km away and 600 meters up from the launch point before its battery was half exhausted and I had to turn it back. But the video and RC control were still great at that distance, so I was unable to determine the absolute range of this setup. Enjoy the video recovered from the GoPro:

Other Hardware Used

Airframe: ArduPhantom (DJI Phantom case, stock ESC, props, and battery)
Motors: T-Motor MN2214 upgrade for DJI Phantom
Autopilot: 3DR APM 2.5 with ArduCopter 3.0.1 firmware
Gimbal: Hummer 2-axis brushless gimbal for DJI Phantom
Camera: GoPro Hero 3 Silver
GPS: 3DR ublox LEA-6H
Telemetry: 3DR 433 MHz
R/C: FlySky TH9X(ER9X FW) + 2.4GHz FrSky DJT module, V8R7-II rx
FPV: ImmersionRC 5.8GHz 600mA tx + CL antenna, FatShark Predator goggles
Ground station: Mavbot Finder