Mavic2 Radio & Antenna Mods

beanbubba · Oct 5, 2018

beanbubba said:
It is not a simple math equation. When using high gain directional antennas on one end of a point-to-point radio link, you can jack the signal and not worry about matching the other side (to a point). This typically only works in fixed radio/antenna positions, and when one or both of the radios is in motion/mobile, you absolutely need to match the radio capabilities on both sides of the link as close as possible.

But we are in strange territory here and fly our birds in perfectly straight lines and keep our remote antennas perfectly gazed on the air craft target. Therefore you can jack up the radio power and or antenna gain on both sides of the link as much as you can afford and you will still see benefit**.

**the bird side antenna needs to stay low gain omni - this is beyond the scope of this thread to explain.

To add some more color to the discussion... You have multiple "links" in a point-to-point radio system "chain". And you always pay most attention to the weakest "link" first, otherwise it is wasted effort to make other links stronger if you do not address the weakest first. The weakest link in our chain is the aircraft transmit/TX abilities. The RC TX and RX is more than adequate (with the sunhans 10W amp) and the aircraft RX is barely good enough. So we first flipped the aircraft antenna 180 degrees that will position the antenna vertically during normal forward flight. Then we added the bird side sunhans 3W amp that significantly bumped up the TX output and gave a bump in RX gain.

The aircraft is still by far the weakest link in the chain after these mod's, but it is MUCH better than before. Point being, there is approaching zero benefit upgrading the RC amp or antenna past the sunhans 10W and 14dBi panel antenna, until you can improve the aircraft TX output. I am trying to better answer Lolo's initial question. You could put a 20W amp on the RC and you would see incremental improvements, but we are now at the point of diminishing returns for RC upgrades until the AC can be correspondingly upgraded too.

SkyNinja · Oct 8, 2018

CyberNate said:
You can permanently force 2.4GHz by pairing the original DJI Goggles as the second Occusync device. This disables 5.8GHz band, even if you are not using goggles. I noticed this when I tried to use 5.8 and go app stated that I need to re-pair controller to enable 5.8. It wouldn't allow me to switch to dual or 5.8 mode.

Nate, can you explain the process you did to pairing the original goggles to maintain 2.4ghz? I’ve tried but I’m not having any luck maintaining 2.4 GHz.

CyberNate · Oct 8, 2018

SkyNinja said:
Nate, can you explain the process you did to pairing the original goggles to maintain 2.4ghz? I’ve tried but I’m not having any luck maintaining 2.4 GHz.

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I'll have to try it again. I have since re-pair controller to get 5.8 GHz band back. All I did was pair the Goggles as the secondary device. After that I only had 2.4 GHz.

CyberNate · Oct 8, 2018

CyberNate said:
I'll have to try it again. I have since re-pair controller to get 5.8 GHz band back. All I did was pair the Goggles as the secondary device. After that I only had 2.4 GHz.

I did fly with goggles once after pairing, but that shouldn't matter.

SkyNinja · Oct 8, 2018

CyberNate said:
I'll have to try it again. I have since re-pair controller to get 5.8 GHz band back. All I did was pair the Goggles as the secondary device. After that I only had 2.4 GHz.

Nate, I did a short flight with the goggles and change Go4 app to 2.4GHz with no loss of signal. When I restarted everything after the flight the Go4 app when back to dual.

When you open the Go4 app Does it say 24GHz or does it say Dual and you know it is staying on 2.4GHz by the goggle Signal?

mlash · Oct 15, 2018

beanbubba said:
@fileophile I see my favorite cable supplier now sells pre-made LMR195 coax with QMA connectors in case you still needed a source:

195 Series QMA Plug to QMA Plug Radio Pigtails

beanbubba, is there a very noticable difference comparing the 10' cables: LMR195 to the RG316?

mlash · Oct 15, 2018

SkyNinja said:
Nate, I did a short flight with the goggles and change Go4 app to 2.4GHz with no loss of signal. When I restarted everything after the flight the Go4 app when back to dual.

When you open the Go4 app Does it say 24GHz or does it say Dual and you know it is staying on 2.4GHz by the goggle Signal?

I paired my goggles the other day and didn't fly until today. Just checked tonight and it is still asking me to "re-pair" remote to bring back the 5.8GHz.

Edit: I've shut everything down a couple times and it still remains asking me to re-link the remote to get back the 5.8!

SkyNinja · Oct 15, 2018

mlash said:
I paired my goggles the other day and didn't fly until today. Just checked tonight and it is still asking me to "re-pair" remote to bring back the 5.8GHz.

Edit: I've shut everything down a couple times and it still remains asking me to re-link the remote to get back the 5.8!

View attachment 50152

****, I’ve never gotten that message. I’m going to try to unsync in resync my goggles and see if that works.

beanbubba · Oct 15, 2018

mlash said:
beanbubba, is there a very noticable difference comparing the 10' cables: LMR195 to the RG316?

No. On short cables there isn't enough loss difference to worry about.

beanbubba · Oct 26, 2018

I had some radio related updates on this other thread that over lapped here at this post and a few after that:

Mavic2 Motor Mods

beanbubba · Nov 23, 2018

Had to replace my old iPad-mini with an iPad to handle the M2. I had to rebuild my traveling rig in the process and here is some show-n-tell of my favorite parts to build the system:

DrPhilGood · Dec 4, 2018

Kilrah said:
Ugh, they went back to these usually ****** toy stick assemblies

cos cheap. Think of all the PS/XB controllers out there.

Deadleg · Dec 27, 2018

Can I ask you guys a general question: I notice antennas sometimes quote a maximum input power. For instance, the Aruba antenna that you use, beanbubba, has an input power spec of 6 watts, but you are driving it with a 10 watt amp. Is there any chance of overloading the antenna and causing distortion, or even damage, if you feed it with too much power? I'm also wondering how much power you can feed to the birdside antenna (no idea what the spec is).

beanbubba · Dec 27, 2018

Deadleg said:
Can I ask you guys a general question: I notice antennas sometimes quote a maximum input power. For instance, the Aruba antenna that you use, beanbubba, has an input power spec of 6 watts, but you are driving it with a 10 watt amp. Is there any chance of overloading the antenna and causing distortion, or even damage, if you feed it with too much power? I'm also wondering how much power you can feed to the birdside antenna (no idea what the spec is).

No, you can never damage the antenna like this.

I suspect that 6W max in the data sheet was all they tested. Typically, the antennas FAR exceed the specifications of the radios attached to them. Anyway, that is right about what we tested out at on the spectrum analyzer. You do no need to worry at all about this particular data point, I promise

Deadleg · Dec 27, 2018

beanbubba said:
No, you can never damage the antenna like this.

I suspect that 6W max in the data sheet was all they tested. Typically, the antennas FAR exceed the specifications of the radios attached to them. Anyway, that is right about what we tested out at on the spectrum analyzer. You do no need to worry at all about this particular data point, I promise

Many thanks

Deadleg · Dec 30, 2018

beanbubba said:
No, you can never damage the antenna like this.

I suspect that 6W max in the data sheet was all they tested. Typically, the antennas FAR exceed the specifications of the radios attached to them. Anyway, that is right about what we tested out at on the spectrum analyzer. You do no need to worry at all about this particular data point, I promise

So the antennas look safe, but what about amp input levels? My Sunhans 3W have an input spec of 0-20 dBm. Mavic 2 RC spec gives 26 dBm max FCC transmission power. Forced boost could push that up to 32 dBm. Is there a danger of overloading the amp? I like the idea of forced boost, because of the bird-side transmitter boost, but will I need to attenuate the RC output to avoid overloading the amp, and by 12 dB?

beanbubba · Dec 30, 2018

Deadleg said:
So the antennas look safe, but what about amp input levels? My Sunhans 3W have an input spec of 0-20 dBm. Mavic 2 RC spec gives 26 dBm max FCC transmission power. Forced boost could push that up to 32 dBm. Is there a danger of overloading the amp? I like the idea of forced boost, because of the bird-side transmitter boost, but will I need to attenuate the RC output to avoid overloading the amp, and by 12 dB?

You ask very good questions. I have tested every possible radio mod on the mavic and the DJI published FCC max of 26 dBm only happens in very brief moments of RC controls and telemetry (all video stream is at much lower power levels). All the amps positively have a max input dBm that they support and they also build in a ~20% buffer and these stats are meant for a 100% duty cycle. The mavic and its RC have tiny/breif moments of 26 dBm TX which equate to ~0.01% duty cycle. With all the mavic's and all the known amp's recently tested, you won't ever harm these amps with too much input power from the mavic or RC. I promise, been there, done that...

This thread has tons of info on these topics if you have not seen it:

Mavic Radio Mods Primer

Deadleg · Dec 30, 2018

beanbubba said:
You ask very good questions. I have tested every possible radio mod on the mavic and the DJI published FCC max of 26 dBm only happens in very brief moments of RC controls and telemetry (all video stream is at much lower power levels). All the amps positively have a max input dBm that they support and they also build in a ~20% buffer and these stats are meant for a 100% duty cycle. The mavic and its RC have tiny/breif moments of 26 dBm TX which equate to ~0.01% duty cycle. With all the mavic's and all the known amp's recently tested, you won't ever harm these amps with too much input power from the mavic or RC. I promise, been there, done that...

This thread has tons of info on these topics if you have not seen it:

Mavic Radio Mods Primer

Thanks again . . sorry if I'm going over old ground. Lots to read. I saw your test results on the Mav 2 radio, and it seems that forced boost is a good idea, if I can make it work. No need for attenuator, and stronger return signal from bird. I also gather from your tests that, like the M1, you only need one antenna for distance, and on the M2 it's the RH antenna. I must thank you for doing these tests, and for presenting your results so clearly.

Deadleg · Jan 22, 2019

Another design question: I want to mount an antenna on the roof of the car, with about 3m cable length. Currently testing different antenna/cable combinations. Does anyone have experience with this? I'm wondering if it's best to put the amp right next to the antenna, or leave it with the RC. I can do either, but not sure which is best.

Also has anyone tried the cheap 5W 5.8 MHz amp (~€40) from Aliexpress? I live in a congested 2.4 area, and want to see how well 5.8 works. I'm getting sporadic loss of video at 4 Km using 3W Sunhans, 2.4 GHz, and a/c set to fcc. Using stock RC on fcc I can get double this range on dual setting.

One other thing: Using cheap Chinese cable and connectors, because they can be ready-made to my length . . . but suspicious of results. Is this stuff ok, or better to use something else?

beanbubba · Jan 22, 2019

Deadleg said:
Another design question: I want to mount an antenna on the roof of the car, with about 3m cable length. Currently testing different antenna/cable combinations. Does anyone have experience with this? I'm wondering if it's best to put the amp right next to the antenna, or leave it with the RC. I can do either, but not sure which is best.

Also has anyone tried the cheap 5W 5.8 MHz amp (~€40) from Aliexpress? I live in a congested 2.4 area, and want to see how well 5.8 works. I'm getting sporadic loss of video at 4 Km using 3W Sunhans, 2.4 GHz, and a/c set to fcc. Using stock RC on fcc I can get double this range on dual setting.

One other thing: Using cheap Chinese cable and connectors, because they can be ready-made to my length . . . but suspicious of results. Is this stuff ok, or better to use something else?

I have tested many and this unit is the best roof mount omni out there. Don't try and make your own RF coax cables, buy what you need made from the factory (so double check all your connector types and gender when ordering. Place the amp near or on the RC.

2.4 GHz MGUR Series Vehicle Mount Omni Antennas