Mavic pro battery & antenna mod!!!!!!!!!!!!!!!

[beanbubba]

Actually, I wanted to ask you about amplifiers. The Sunhams 3W amp is only putting out 170mW. Do we need preamps to get the full 3W? It's basically 4 times the power of the controller, giving more than double the range when coupled with higher gain antenna, but still a tiny fraction of advertised power. I wonder if one could put the Sunhams amps in series to get full power. The first would act as the preamp. I suppose it might be to strong in preamp role, exceeding input maximum on the the second amp.

Cybernate, please help get me up to speed on this topic.

This is the first I have heard the the sunhams effective output is 170mW, how did you conclude this? I do not have one to test, but I just ordered a pair from amazon right now with delivery Friday and I will verify this coming weekend.

I am currently using 250mW amps from Hyperlink that easily handle the 6 mile run I just completed. If I had line of sight, these could just about handle 10 miles. The 3 watt amp's are complete overkill on paper, but I am intrigued why you suspect that the sunhams are only 170mW.

These are some examples of the amp's that I use in my day job:
WiFi Booster | WiFi Amplifier | WiFi Extender | L-com

Regarding your question about pre-amp's, this is not something that is practiced in this discipline. All of these devices have a receiver sensitivity and can easily be damaged if you exceed their rated input values. There are devices available to match any situation you could ever need in RF link budget planning and using pre-amp's is not something that is practiced because it adds unnecessary attenuation that can be easily avoided. I can help you with the RF math on how all this works and the parts required to accomplish the desired goal.

 

[CyberNate]

Cybernate, please help get me up to speed on this topic.

This is the first I have heard the the sunhams effective output is 170mW, how did you conclude this? I do not have one to test, but I just ordered a pair from amazon right now with delivery Friday and I will verify this coming weekend.

I am currently using 250mW amps from Hyperlink that easily handle the 6 mile run I just completed. If I had line of sight, these could just about handle 10 miles. The 3 watt amp's are complete overkill on paper, but I am intrigued why you suspect that the sunhams are only 170mW.

These are some examples of the amp's that I use in my day job:
WiFi Booster | WiFi Amplifier | WiFi Extender | L-com

Regarding your question about pre-amp's, this is not something that is practiced in this discipline. All of these devices have a receiver sensitivity and can easily be damaged if you exceed their rated input values. There are devices available to match any situation you could ever need in RF link budget planning and using pre-amp's is not something that is practiced because it adds unnecessary attenuation that can be easily avoided. I can help you with the RF math on how all this works and the parts required to accomplish the desired goal.

Well I'm going off the measurement that @JakeMaxxUAV made in this post:
NanoSync Antenna for DJI Mavic Coming Soon

I'm not sure what he used for input on the Sunhams. I've seen the output on the controller measured at 45mW for FCC power level, while Jake measured 170mW off Sunhams output.

 

[GTMonster]

With regards to the Mavic FPVLR long range antennas...
* Now Available!* DJI MAVIC PRO 8dBi Long Range antenna - FPVLR

I have been browsing this thread briefly. I have noted the FPVLR long range antennas that are being mentioned as pictured earlier in the thread and I apologise in advance if the below has already been mentioned.

The FLPLR antennas shown are a vertically polarised Yagi antenna type antenna (This is the type of antenna used on the roof of your house for TV reception but with less elements. On the roof of your house it is horizontally polarised). It basically consists of a tuned dipole antenna and an array of elements. In this application it is of a slightly unusual configuration with the elements of the antenna and the dipole angled forward (I'm not sure if this is to further focus the transition or alter its polarisation slightly for better signal rejection). If the dipole part of the antenna and the rest of the elements are tuned correctly to the middle of the controllers 2.4GHz transition bandwidth, then the antenna will be focusing the emitted EM field primarily in a forward direction appearing almost like a long narrow rain drop (round end of the rain drop pointing forward to the craft with the sharp end at the antenna). As the antenna has designed gain of 8db then the effective radiated power (ERP) will be amplified in a forward direction. This should extend the range slightly, but more importantly provides better signal strength and quality at all distances within the range of the standard antennas (currently on the remote) functionality. This last point for me was the most important... better signal strength at closer range than the standard antenna equals less signal dropout and greater signal penetration! The extended range is just to sell this to the people that only hear the word 'range'

With a standard antenna the EM field will be emitted equally in all directions around the antenna sort of like a ring donut. As the field from the standard antenna is not focussed it will dissipate quicker as it is dispersed over a greater area.

The FPVLR antenna is like shouting using hands cupped around your mouth to focus your voice.

The advantage of the Yagi design is that the transmitted signal is stronger in a forward direction, however it is important to point the controller in the direction of the craft for best signal. Signal will dissipate quickly behind the antennas so be careful.

With the standard remote antennas, the signal is omnidirectional so if accidentally flying behind yourself, then a reasonable amount of signal will be getting to the craft.

I've just rushed this in my dinner so will reread later to confirm that I am happy that I have written this correctly. If I am wrong, please let me know. I like to learn and I'm open to civil discussion and wisdom!

I have nothing to do with the designers of this antenna and am not endorsing it, however if they are happy with this I will accept payment or a free set of these Mavic antennas! (I can wish ;-Þ)

I hope this helps someone or gives direction for research.

 

[sprtbkrydr]

ordered a pair from amazon right now with delivery Friday and I will verify this coming weekend.

If you don't mind when you post the findings I'm curious as to how much current these amps require for full power out.

 

[GTMonster]

If you don't mind when you post the findings I'm curious as to how much current these amps require for full power out.

If I remember correctly... in this application, the power output of the transmitter would be fixed and therefore current draw would not change in the output stages of the remote. The antenna would effectively be amplifying outputted field strength in a given direction by focussing it.
From memory, if both antennas were operating side by side and a line was drawn along the path of highest field strength emanating from the long range directional antenna, then at any given point on this path, the 8db antenna would have approximately 6 times the signal strength of the non-directional antenna (The antenna would need to be pointed at the craft for full gain to be seen).

 

[CyberNate]

With regards to the Mavic FPVLR long range antennas...
* Now Available!* DJI MAVIC PRO 8dBi Long Range antenna - FPVLR

I have been browsing this thread briefly. I have noted the FPVLR long range antennas that are being mentioned as pictured earlier in the thread and I apologise in advance if the below has already been mentioned.

The FLPLR antennas shown are a vertically polarised Yagi antenna type antenna (This is the type of antenna used on the roof of your house for TV reception but with less elements. On the roof of your house it is horizontally polarised). It basically consists of a tuned dipole antenna and an array of elements. In this application it is of a slightly unusual configuration with the elements of the antenna and the dipole angled forward (I'm not sure if this is to further focus the transition or alter its polarisation slightly for better signal rejection). If the dipole part of the antenna and the rest of the elements are tuned correctly to the middle of the controllers 2.4GHz transition bandwidth, then the antenna will be focusing the emitted EM field primarily in a forward direction appearing almost like a long narrow rain drop (round end of the rain drop pointing forward to the craft with the sharp end at the antenna). As the antenna has designed gain of 8db then the effective radiated power (ERP) will be amplified in a forward direction. This should extend the range slightly, but more importantly provides better signal strength and quality at all distances within the range of the standard antennas (currently on the remote) functionality. This last point for me was the most important... better signal strength at closer range than the standard antenna equals less signal dropout and greater signal penetration! The extended range is just to sell this to the people that only hear the word 'range'

With a standard antenna the EM field will be emitted equally in all directions around the antenna sort of like a ring donut. As the field from the standard antenna is not focussed it will dissipate quicker as it is dispersed over a greater area.

The FPVLR antenna is like shouting using hands cupped around your mouth to focus your voice.

The advantage of the Yagi design is that the transmitted signal is stronger in a forward direction, however it is important to point the controller in the direction of the craft for best signal. Signal will dissipate quickly behind the antennas so be careful.

With the standard remote antennas, the signal is omnidirectional so if accidentally flying behind yourself, then a reasonable amount of signal will be getting to the craft.

I've just rushed this in my dinner so will reread later to confirm that I am happy that I have written this correctly. If I am wrong, please let me know. I like to learn and I'm open to civil discussion and wisdom!

I have nothing to do with the designers of this antenna and am not endorsing it, however if they are happy with this I will accept payment or a free set of these Mavic antennas! (I can wish ;-Þ)

I hope this helps someone or gives direction for research.

I have many sets of antenna including these FPVLR ya go type. They are descent, but no where near as good as the RexUAV

With regards to the Mavic FPVLR long range antennas...
* Now Available!* DJI MAVIC PRO 8dBi Long Range antenna - FPVLR

I have been browsing this thread briefly. I have noted the FPVLR long range antennas that are being mentioned as pictured earlier in the thread and I apologise in advance if the below has already been mentioned.

The FLPLR antennas shown are a vertically polarised Yagi antenna type antenna (This is the type of antenna used on the roof of your house for TV reception but with less elements. On the roof of your house it is horizontally polarised). It basically consists of a tuned dipole antenna and an array of elements. In this application it is of a slightly unusual configuration with the elements of the antenna and the dipole angled forward (I'm not sure if this is to further focus the transition or alter its polarisation slightly for better signal rejection). If the dipole part of the antenna and the rest of the elements are tuned correctly to the middle of the controllers 2.4GHz transition bandwidth, then the antenna will be focusing the emitted EM field primarily in a forward direction appearing almost like a long narrow rain drop (round end of the rain drop pointing forward to the craft with the sharp end at the antenna). As the antenna has designed gain of 8db then the effective radiated power (ERP) will be amplified in a forward direction. This should extend the range slightly, but more importantly provides better signal strength and quality at all distances within the range of the standard antennas (currently on the remote) functionality. This last point for me was the most important... better signal strength at closer range than the standard antenna equals less signal dropout and greater signal penetration! The extended range is just to sell this to the people that only hear the word 'range'

With a standard antenna the EM field will be emitted equally in all directions around the antenna sort of like a ring donut. As the field from the standard antenna is not focussed it will dissipate quicker as it is dispersed over a greater area.

The FPVLR antenna is like shouting using hands cupped around your mouth to focus your voice.

The advantage of the Yagi design is that the transmitted signal is stronger in a forward direction, however it is important to point the controller in the direction of the craft for best signal. Signal will dissipate quickly behind the antennas so be careful.

With the standard remote antennas, the signal is omnidirectional so if accidentally flying behind yourself, then a reasonable amount of signal will be getting to the craft.

I've just rushed this in my dinner so will reread later to confirm that I am happy that I have written this correctly. If I am wrong, please let me know. I like to learn and I'm open to civil discussion and wisdom!

I have nothing to do with the designers of this antenna and am not endorsing it, however if they are happy with this I will accept payment or a free set of these Mavic antennas! (I can wish ;-Þ)

I hope this helps someone or gives direction for research.

I have a set of these FPVLR antenna. They work decently well. They are better than stock unboosted for sure. For boosting, they don't work as well. I've found too much interference with this type boosted, resulting in poor video quality. For me the Circular Polarizing type work much better as with RexUAV or the FPVLR model which was originally for the 3DR solo which is also circular polarized.

 

[GTMonster]

I have many sets of antenna including these FPVLR ya go type. They are descent, but no where near as good as the RexUAV



I have a set of these FPVLR antenna. They work decently well. They are better than stock unboosted for sure. For boosting, they don't work as well. I've found too much interference with this type boosted, resulting in poor video quality. For me the Circular Polarizing type work much better as with RexUAV or the FPVLR model which was originally for the 3DR solo which is also circular polarized.

The down side to adding boosters to the Mavic that it effectively makes the setup less portable which IMO is the point of the Mavic.

Circular polarisation will provide better unwanted signal rejection than linear polarised antennas, however for correct functionality both the transmitter and receiver require circular polarised antennas. This which would require modification of the antennas on the craft as well as at the controls.

 

[CyberNate]

The down side to adding boosters to the Mavic that it effectively makes the setup less portable which IMO is the point of the Mavic.

Circular polarisation will provide better unwanted signal rejection than linear polarised antennas, however for correct functionality both the transmitter and receiver require circular polarised antennas. This which would require modification of the antennas on the craft as well as at the controls.

True, but it's phenomenal already even with polarization mismatch. It also works well unboosted.

 

[GTMonster]

True, but it's phenomenal already even with polarization mismatch. It also works well unboosted.

I've found using them CP on my racing quads really improves signal quality. I use IBCrazy Mad Mushrooms Right circular polorised mostly. But I found using a miss matched set of linear and circular reduces effectiveness considerably though you will still get a signal.

 

[CyberNate]

I've found using them CP on my racing quads really improves signal quality. I use IBCrazy Mad Mushrooms Right circular polorised mostly. But I found using a miss matched set of linear and circular reduces effectiveness considerably though you will still get a signal.

Well, I get solid signal at 54,000ft across silicon valley, so i guess it's barely working.

 

[GTMonster]

Thats some cool flight distance. I'm jealous! I've been considering doing similar for a while but its not possible in the UK with the available frequencies here and the power available on those frequencies.

That's also either a fair bit more powerful TX than I'm using on 5.8GHz or I'm guessing a far lower frequency with better penetration. I'm not so lucky round my way as in the past few years 5.8GHz has become more popular with WiFi users and in the UK lower frequencies are not free to use due to being utilised by other UK services. We are 'meant' to be limited to 25mW on 2.4 and 5.8 which really sucks. I can transmit on my HAM radio at 10W legally on these chanels. But its illegal to transmit on a HAM radio licence from the air!

 

[beanbubba]

Well, I get solid signal at 54,000ft across silicon valley, so i guess it's barely working.

I have been researching and this article summarizes the debate pretty well:

Circular or Linear Polarized Antenna For FPV - Oscar Liang

I have little experience with CP antennas, so I have ordered several models and look forward to testing and comparing.

Hey Cybernate, when you are at 54,000', how many bars of signal show on your remote controller?

 

[CyberNate]

I have been researching and this article summarizes the debate pretty well:

Circular or Linear Polarized Antenna For FPV - Oscar Liang

I have little experience with CP antennas, so I have ordered several models and look forward to testing and comparing.

Hey Cybernate, when you are at 54,000', how many bars of signal show on your remote controller?

I can't remember, but I have perfect video and control feed the entire flight and flew at 260ft all the way out.

 

[beanbubba]

I can't remember, but I have perfect video and control feed the entire flight and flew at 260ft all the way out.

Is it on youtube?

 

[CyberNate]

Is it on youtube?

No I can't post that. I was flying over urban environment. Don't want to draw attention to that. I did post some of the video in a secret group, but I won't make it public.

 

[beanbubba]

Well I'm going off the measurement that @JakeMaxxUAV made in this post:
NanoSync Antenna for DJI Mavic Coming Soon

I'm not sure what he used for input on the Sunhams. I've seen the output on the controller measured at 45mW for FCC power level, while Jake measured 170mW off Sunhams output.

Cybernate, I am still researching your 170mW statement (and getting the signal bar readout on your 54,000' run will help greatly). On your other statement, was the 45mW measured at the radio board, or out the factory antenna?

 

[CyberNate]

Cybernate, I am still researching your 170mW statement (and getting the signal bar readout on your 54,000' run will help greatly). On your other statement, was the 45mW measured at the radio board, or out the factory antenna?

45mW was measured off radio board, before antenna. There was an RP-SMA connector fitted on controller.

 

[Brojon]

Just my 2 cents - I keep seeing people refer to the antenna design in the original post as a "yagi". It is not.
A yagi has multiple elements to focus the beam forward. The pic in the original post appears to be a simple dipole in a "V" configuration with passive radiator. Maybe a small distinction but it defines the likely beam pattern should anyone care to look it up.
Y'all seen those Polar Pro antenna passive reflectors? Same principle. There was a free mod for wifi way back call the "WindSurfer". Same thing. I wouldn't doubt that Polar Pro resurrected that design for their product.
Anyway it would be likely that those would provide the same or better antenna gain.
Did a quick search - yup, you can build one for free. I made one for wifi ages ago and used stainless tape from Home Depot on heavy stock to make mine.

Make your own passive radiators for Mavic

 

[beanbubba]

45mW was measured off radio board, before antenna. There was an RP-SMA connector fitted on controller.

Cybernate, I have no doubt you witnessed that, but I would like to see the setup and check the calibration of the testing equipment. DJI publishes on the mavic datasheet 26 EIRP.

EIRP = Radiated power output from antenna ( Transmitter (dBm) - Cable_Loss (dB) - Connector_Loss (dB) + Antenna_Gain (dBi) )

Making a safe assumption that the controller has 0.5 db loss in cable/connectors and 3.8 dBi antenna gain, that would equate to the radio transmitter at 22.7 dBm, or 186 mW.

45mW is only around 1/4 of the FCC allowed EIRP for this type of setup. It is possible that DJI may dynamically adjust transmit power when the aircraft moves away from the remote. I know other technologies do this, but I am purely speculating trying to understand this low measured power output.

 

[GTMonster]

Just my 2 cents - I keep seeing people refer to the antenna design in the original post as a "yagi". It is not.
A yagi has multiple elements to focus the beam forward. The pic in the original post appears to be a simple dipole in a "V" configuration with passive radiator. Maybe a small distinction but it defines the likely beam pattern should anyone care to look it up.
Y'all seen those Polar Pro antenna passive reflectors? Same principle. There was a free mod for wifi way back call the "WindSurfer". Same thing. I wouldn't doubt that Polar Pro resurrected that design for their product.
Anyway it would be likely that those would provide the same or better antenna gain.
Did a quick search - yup, you can build one for free. I made one for wifi ages ago and used stainless tape from Home Depot on heavy stock to make mine.

Make your own passive radiators for Mavic

Now you've said this, I stand corrected... it can't be a Yagi as there would also need to be a reflector behind the dipole and at least one radiator in front of the dipole. There are only 2 linear parts to this antenna. I may get one to have a
play with. Once fitted I'd then have the screw connectors in place so would be open to other antenna options.