Aircraft Antenna Mod

[Haloweenhamster]

Which aircraft antennas do people rate the best for general flying? Not to directional

what thermal compound do you use when reassembling?
Been advised no silicon, and thought silver stuff has to much capacitance or electrically conductive

Thanks

 

[MacIak]

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!!

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Just checking back onto this thread (and I heard what you said about me and MM!). Great piece of work you got there. Good hope for the ones that need to beam thru trees! Stronger onboard TX is the answer for sure.
Not much time for me to play these days.

 

[MacIak]

Sorry to beat a dead horse, but this is confusing a lot of folks.

I believe Maciak and others only refer to TX/RX in relation to the remote controller. Throughout this entire thread I have been using TX/RX (radio transmit and radio receive) from the aircraft radio perspective. From my view the aircraft onboard radio needs stronger RX (not TX) and same for the remote controller too.

Nobody is right or wrong here, just explaining different viewpoints on a confusing topic.

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Bub you just woke up or somethin' ? Now you confused EVERYONE! You wanna pump watts into the Aircraft TX (transmitter) and the remote TX.
I also use TX/RX from the point of the unit under mod which in this case is the aircraft.

 

[beanbubba]

I have been told I do that sometimes . Let me try to re-word a response.

 

[beanbubba]

I removed the guts of the amp from the heavy case and shed 34 grams!!

The entire mod is down to 24 grams.

The board is so light that the seated power cable firmly holds it in place enough that I was not at all worried it would come loose in flight. I just completed a 5 mile out run with it and works great.

NOTE: you do have to re-solder the RPSMA connectors and solder a tiny ground wire to the ground on the board.

 

[RolandS888]

That wont work very well. The case forms a shield to keep the noise IN and provides a common ground between input and output. You fly with that the way it is and your range will be severely reduced as the noise from the exposed board will drown out your transmitted signal from the ground. .
A little bit of knowledge is a dangerous thing.

And yes, you need to join the outside of the connectors together, and ground the board as well, at the very least.
Still a very bad idea. Leave the case on.

 

[beanbubba]

I just did a range test and had identical results. Well before this test, I concluded long ago that I had to position the amp in the sidecar position. Any other position had severe RF interference.

Just flew this a couple hours ago, results don't lie.

Airdata UAV - Flight Data Analysis for Drones

I did have to solder the ground to the board:

 

[beanbubba]

That wont work very well. The case forms a shield to keep the noise IN and provides a common ground between input and output. You fly with that the way it is and your range will be severely reduced as the noise from the exposed board will drown out your transmitted signal from the ground. .
A little bit of knowledge is a dangerous thing.

And yes, you need to join the outside of the connectors together, and ground the board as well, at the very least.
Still a very bad idea. Leave the case on.

Here are the airdata results. I had nearly identical RF performance on both flights. I am surrounded by trees and fly as low as I can until I nearly lose signal. For whatever reason, I did not experience any negative effects. I suspect that in the sidecar orientation, that the battery shields the amp enough from the main boards.

 

[Haloweenhamster]

If you are worried about interference just insulate with something like Mylar and wrap some foil around it

I've had to do it to a few DC/DC converters in the past

 

[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.

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If anyone wants to attempt this mod, the pictures in this post are incorrect. The correct setup places the amp on the other side of the bird (port side using the black coax cable from the mavic antenna). I mistakenly used this picture when I removed one of the amps from previous tests and I forgot to update this thread. I have been flying daily since then with the amp on the port side and can assure you this is the configuration required to gain the bird side TX benefits.

 

[beanbubba]

PART-1

I have been wanting to do this mod for months but my day job kept getting in the way. Having a week off for the holidays gave me some time to play this out and leverage the efforts in the weight reduction mod in the other thread.

All of us know and love the Sunhams amplifier and use this great product regularly in different configurations. There is another amp that has no brand name but you can find it from many China based sellers. It is recognizable by the jet black case and the shape of a dragon (I think) that makes a heat sink on the front case. This thing weighs a ton and is not suitable for birdside applications.

However, if you take this thing apart it is super light weight and actually out performs the power output of the Sunhams. I measured this months ago with a spectrum analyzer but didn't have the time to properly explore the options for this mod.



I also wanted to explore using a higher gain antenna than the factory ones in the front legs of the Mavic Pro. After examining many different units, I settled on this one that you will find bundled with many products and was popular with phantom mods in the past.



I stripped down the board from the "dragon" amp and direct soldered the antenna and lead to the mavic main board. This saved 10 grams of weight in connectors alone! I then epoxy'd the fragile solder points since the metal case is no longer part of the solution.



This board produces a lot of heat from the TX/RX chips and I fashioned a heat sink from folded up copper tape and covering one side with thermal putty. This saved the upcoming covering from overheating and melting the material.



Continuing this post in part 2 due to the picture limit per post.

 

[beanbubba]

PART-2

Now that the structure of the mod is intact, I decided to use industrial velcro as a super light weight covering for the board and connectors.



This version of the mod only requires a tiny hole drilled through the rear LED lens for the coax cable to connect to the Mavic main board TX/RX connector. Then power the unit by your preferred method (battery clip in this example).



You will notice that the antenna angles ~45 degrees forward and this is to offset the angle of attack the bird has with forward flight. For high gain antennas you need the antenna to be vertical during normal operation to realize the benefit of the mod. A high gain antenna omni coverage pattern is flattened which give greater reach in the horizontal plane (and reduces coverage in the vertical plane). The images below depict a rough estimation between the difference in this mod and the factory antennas on the Mavic.



And finally, this mod weighs in at a minuscule 17 grams!!! This even surprised me and you won't find anything anywhere with the weight/performance of this mod.



I did some preliminary flight tests tests tonight and they exceeded my expectations. I need to do a full battery of long range tests but I am confident that this mod is a keeper.

 

[Banned]

PART-1
I have been wanting to do this mod .

You my friend, win.

 

[lolo780]

@beanbubba what's your opinion on using these for the RC side?

 

[beanbubba]

@beanbubba what's your opinion on using these for the RC side?

They work great for that, but they are very heavy. Some report their longevity isn't as good as the Sunhams, but you can get a half dozen for spares for the same price

 

[lolo780]

They work great for that, but they are very heavy. Some report their longevity isn't as good as the Sunhams, but you can get a half dozen for spares for the same price

I mean uncased. A compact boosted RC on stock antennas would be cool. Power off the internal battery and still fit anywhere a stock RC would normally pack.

 

[beanbubba]

I mean uncased. A compact boosted RC on stock antennas would be cool. Power off the internal battery and still fit anywhere a stock RC would normally pack.

Oh yes, for sure.

When you take it apart and desolder the SMA connectors to get it out of the case, be very very carful. The contact point is just a thin/fragile piece of copper foil. When you solder the connector or coax back on, you must secure it somehow (I used epoxy). If you don't, the solder point will easily rip the foil right off the board and it is not fixable (already been there, done that).

Were you thinking about using the internal RC battery to power the amp?

 

[lolo780]

Oh yes, for sure.

When you take it apart and desolder the SMA connectors to get it out of the case, be very very carful. The contact point is just a thin/fragile piece of copper foil. When you solder the connector or coax back on, you must secure it somehow (I used epoxy). If you don't, the solder point will easily rip the foil right off the board and it is not fixable (already been there, done that).

Were you thinking about using the internal RC battery to power the amp?

Yes. Do you think it can all work? Disabling the charging via usb will free up some battery power.

 

[beanbubba]

Yes. Do you think it can all work? Disabling the charging via usb will free up some battery power.

That's a great idea. And for 95% of folks that use amp'd RC's, the panel antennas are complete overkill when paired with a good amp. We only did it because we had to tear the RC apart, and while it's opened up, you might as well go overkill (I do the same with big panel antennas).

With this alternate configuration you could have a thin and smaller than a credit card device velcro'd to the back of the RC. Have it wired to the factory antenna and RC radio and power supply. And as you say, it fits into any standard case and is super streamlined. Just gut experience with these devices, I bet the "dragon" amp will only degrade the RC battery no more than 20%.

One note for laymen radio enthusiasts. If 2 devices in a full duplex relationship are not equally paired with RF power and antenna characteristics, the lowest common denominator becomes the performance reality. If 2-way radio communications are required, having one end of the link with huge antennas and huge power output does not improve the overall performance of the end2end solution. But I do admit that its a lot of fun to over engineer at every chance I get

Lolo, I am not aware of the USB charging issue. Can you please elaborate?

 

[lolo780]

Just the USB cable trying to charge Android devices.