Aircraft Antenna Mod

[wynnhoj]

Decided to take apart the factory antenna and check it out. Interesting design I have not seen before. They have what looks to be a reflector or similar device sandwiched right next to the antenna in the front leg. Whatever it is DJI came up with a fantastic result. From prior testing, the factory antenna is nearly as good performance as a high gain external 10 times its size.

I rerouted the factory coax cables from the antennas out the topside next to the amp's. I think this will be my final design and waiting on an SMA-U.FL adapter that is on order.

Beautiful work.

Why haven´t you tried using clover leaf antennas?

 

[beanbubba]

Beautiful work.

Why haven´t you tried using clover leaf antennas?

I ordered a pair but they sent me 5.8gHz. Haven't gotten around to hunt down a 2.4 version and I probably won't because the 2.4 varieties are triple the size and too cumbersome for this application.

 

[beanbubba]

Here is the adapter to go straight from the factory antenna to the external amplifier. I could only find a china supplier on eBay.

 

[KD8ICQ]

You guys all need to get on Ham radio so we could all talk together. That's another not so cheap hobby of mine.

KD8ICQ here. Nice to see someone else who shares another elegantly expensive hobby.

73

 

[beanbubba]

I bought the payload release kit from:

Gimbal-Guard

And just started to play around with ideas for the battery jettison idea. With little to no changes, you could literally hang the 5.2 LiHv from the mechanism and have it swinging in the wind. The drag from this would be considerable and a fair chance of it getting tangled in the wind. But in this thought experiment, I would make an educated guess that you could add a couple miles to a range run test and jettison the battery around the turn around point. Lube up the battery connectors with dielectric grease and the battery should come clean loose after the servo releases the load when the front lights are activated from the remote controller.

Something to ponder and continue to figure out a way to streamline this idea.

 

[beanbubba]

I bought the payload release kit from:

Gimbal-Guard

And just started to play around with ideas for the battery jettison idea. With little to no changes, you could literally hang the 5.2 LiHv from the mechanism and have it swinging in the wind. The drag from this would be considerable and a fair chance of it getting tangled in the wind. But in this thought experiment, I would make an educated guess that you could add a couple miles to a range run test and jettison the battery around the turn around point. Lube up the battery connectors with dielectric grease and the battery should come clean loose after the servo releases the load when the front lights are activated from the remote controller.

Something to ponder and continue to figure out a way to streamline this idea.

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I would challenge wynnhoj to consider adding one additional servo to his contraption design to accommodate the option for a battery jettison solution.

 

[beanbubba]

Could anyone help me with a delicate problem:

If we use a helical antenna with 60* angle i should mount it 90* because after 1km the base of the cone should be apprx 1.1km right? Only problem as I see it is that we get theoretically radio shadow within a radius of apprx 400m.

I found this illustration on the RC forums from the user Aspranger.
"Lets assume you had a combo of a CL and a Helical Antenna, then this image would show the areas, where you'd have video reception when using e.g. a 100mw tx like I do.

The green circle shows the area of the CL Antenna, using this, you can pretty much fly around your ground station in any direction, as long as you stay in the green circle. Even though the range is limited.

On the left you can see the Gain pattern of a 4 turn Helical. As you can see, you can fly further out, but the further you fly, the narrower becomes the area in front of you, where you'd have good reception of your video signal. With the 4 turn, the beam is very wide, thus it is suficcient, if the antenna points in the aproximate direction of your plane, or you can put the antenna on a fixed stand and fly everywhere in front of it, as long as you stay in the red area.

On the right you can see a high Gain pattern of a e.g. 9 turn helical. Due to the higher gain, the max range rises ( every 6 dbi the range is doubled ) but due to the strongly directional gain pattern of the antenna, you need to be carefull where you fly, or better have a spotter or an antenna tracker, pointing your antenna in the right direction."

Below is a 3D visualization of a 30x30 degree 2.4 gHz panel antenna coverage pattern. It doesn't take a rocket scientist to figure out where your bird needs to be for a strong signal. The holy grail would be to have the bird and the home point remote both with high gain directional antennas pointed at each other at all times.

Circular polarized antennas have great value for close range performance flying, but I have found little additional benefit over vertically polarized directional panel antennas for this application. I encourage you to test and investigate but I doubt there will be a significant improvement. I challenge you to prove me wrong!

 

[MesaAZGuy]

Totally impressive!! I read through this whole thread. Awesome work and dedication. I too, would love to get more range. I wouldn't mind starting off with a base station antenna system. My area is pretty flat but i still get interference when less than a mile away and have to return. Really frustrating.

 

[Samuelson]

After some advice guys.
Tried installing 2 of the cheap 4w amps from AliExpress to my RC that already had a nanosync installed and was working brilliant on its own.

The amps I could never get both to work at the same time only 1 would ever give a green led to show connected.

So I removed the amps and went back to the nanosync on its own.
Now I'm struggling to even get a mile in rural conditions.

I have checked the cables and stripped the RC down to check there but still the same.
Is there a way to test the signal strength without specialized equipment or could I have fried the nanosync??
Any ideas. My brain is starting to hurt

 

[beanbubba]

The darn antenna adapters from China FINALLY showed up. I will get this tested by tomorrow. I have high hopes this is the final and best configuration for this mod. I will probably sugru the adapters in place with the factory antenna coax and hopefully protect the fragile U.FL connectors.

 

[beanbubba]

Here is the mod total weight for reference:

 

[MrsTreat]

The darn antenna adapters from China FINALLY showed up. I will get this tested by tomorrow. I have high hopes this is the final and best configuration for this mod. I will probably sugru the adapters in place with the factory antenna coax and hopefully protect the fragile U.FL connectors.

View attachment 20726 View attachment 20727 View attachment 20728

Impressive - thinking it will work great!

 

[beanbubba]

***************************************************************************
***********THIS IS THE FINAL MOD FOR THE THREAD***********
***************************************************************************

Alrighty race fans, my final mod configuration is done!!

I had to move the amp from the topside to a sidecar configuration. No matter where I placed it on top, it would interfere with the GPS significantly. And as others have suspected, there is little to no benefit having 2 amp's on the birdside. I actually went down to 1 amp on both the remote controller and aircraft and overall performance was nearly the same.

I am in the middle of running many tests to document this with facts and numbers, but the initial results were good enough to call this mod a big success. I just did a test run out 20,000 feet at 200 feet altitude and lowered my home point mast down to 15 feet. There is a small forest in between and it blasted right through it. This was the intent for this mod, to allow more distance when you live in the woods.

 

[lwg38671]

Alrighty race fans, my final mod configuration is done!!

I had to move the amp from the topside to a sidecar configuration. No matter where I placed it on top, it would interfere with the GPS significantly. And as others have suspected, there is little to no benefit having 2 amp's on the birdside. I actually went down to 1 amp on both the remote controller and aircraft and overall performance was nearly the same.

I am in the middle of running many tests to document this with facts and numbers, but the initial results were good enough to call this mod a big success. I just did a test run out 20,000 feet at 200 feet altitude and lowered my home point mast down to 15 feet. There is a small forest in between and it blasted right through it. This was the intent for this mod, to allow more distance when you live in the woods.

View attachment 20949 View attachment 20950 View attachment 20951 View attachment 20952 View attachment 20953

Does it help to boost the RX side? How does it fly with the amp on one side?

 

[Haloweenhamster]

Thought this would be the place to ask, do you need both aerials?
what's the difference between the white and black?

 

[beanbubba]

Thought this would be the place to ask, do you need both aerials?
what's the difference between the white and black?

The white antenna cable comes from the starboard front leg antenna and is the birdside RX (receive) radio. The black antenna cable comes from the portside front leg antenna and is the birdside TX (transmit) radio.

From extensive testing, the birdside TX radio needs no amplification and it far out performs the RX radio without mod's. After you boost the RX radio, they perform almost identically (assuming you boost the RX radio the same on your remote controller). I have found little to no evidence that amplification of the TX radio on BOTH the bird and remote controller is needed. Many folks do it, but the net gain is tiny and not worth the effort and complexity IMHO.

 

[beanbubba]

Does it help to boost the RX side? How does it fly with the amp on one side?

The amp is so light there is no noticeable effect.

 

[beanbubba]

I took my bird out for a quick 5 miles out and back (with dual 3.0 LiHv's) and at max distance I still had 3/4 bars signal at 400 feet altitude. On this same course before, I had to climb to 1500 feet and only one bar of signal. This is my new long range mod and I am stoked!!

 

[MrsTreat]

I took my bird out for a quick 5 miles out and back (with dual 3.0 LiHv's) and at max distance I still had 3/4 bars signal at 400 feet altitude. On this same course before, I had to climb to 1500 feet and only one bar of signal. This is my new long range mod and I am stoked!!

View attachment 20977

View attachment 20978

Simply awesome!!

 

[Haloweenhamster]

Good to know, cheers
On my original mavic the video dropped out when I still had full RC signal quite a few times, I have just bought a second one second hand crash damaged to try some mods and the left leg is ripped off
The black cable is fine it ripped the pads off the antenna PCB, anyway the center core hadn't been stripped and it was soldered to the insulation.
I wonder if that was the reason my original had such bad signal especially for video