More channels hack

[Foosy]

Foosy, have you tried it? I have read the posts that you have referenced and yours. You guys have valid points...but snake oil or shenanigans... My distance with video on the newly provided manual clean channel have greatly improved with this mod than without. As far as adding a certain amount of channels instead of the full 24...hey it is what it is unless you are a coder with SDK to make changes. Anyone here able to break down the channel spread on how we are getting better results with this hack? Someone has put the effort into providing this config file out for the community that has been jonesing for their 32 channels back. Now we have it and without ill effects. And you want to suggest smelling snake oil? OK I guess. It does take all kinds to make a community.

No, I have not tried it. But I am basing my comments on engineering data, being I am an engineer.
I am not arguing that a certain channel could be less noisy for you. I am arguing, that regardless of which channel you use, if you use a clean channel , either one of the 8 or one of the 32 enabled by the hack, you should get the same result. Whichever channel you use does not, and cannot increase the range.

I see some people have started to do experiments that will prove the point.
So, I also started to think, what could, engeeringly, cause you or others to actually measure a higher range ?
The only thing I can come up with, is if the RF amplifier is not linear, and has more power at certain frequencies. If that particular frequency is the one you are using, you will get more range, as range is a function of power. As a matter of fact, for the range to double, your power would need to quadruple.

 

[N017RW]

While the inverse square law is inescapable, transmit power is only one consideration so the non-linearity (if any) of the amp is really insignificant.
We will also ignore local or ambient conditions as this is difficult to categorize or measure and the receiver specs like sensitivity, selectivity, etc. as that is typically a function of hardware and remains constant with or without the 'hack' as well.

However, Signal to Noise Ratio and the resultant Bit Error Rate is a major contributor to transmission quality and what we experience a 'range'. When the SNR drops below about 20dB the BER increases. At some point the errors are too large to resolve so the data rate must be lowered or a threshold will be crossed and the signal is unusable thus the 'connection' is dropped.
When the SNR is greater than ~20dB the more useable or stable the signal becomes.

Based on data reported here by spectrum analysis it appears the 'hack' has enabled spectrum below and beyond the WLAN band. This moves the LB carriers away from the more congested part of the spectrum. The less 'crowded' the greater the SNR is likely to be which leads to better BER and this is seen as 'range'.

This is a oversimplification to make a point. If anyone can offer more insight please do as I welcome the discourse.

 

[Dronebow]

While the inverse square law is inescapable, transmit power is only one consideration so the non-linearity (if any) of the amp is really insignificant.
We will also ignore local or ambient conditions as this is difficult to categorize or measure and the receiver specs like sensitivity, selectivity, etc. as that is typically a function of hardware and remains constant with or without the 'hack' as well.

However, Signal to Noise Ratio and the resultant Bit Error Rate is a major contributor to transmission quality and what we experience a 'range'. When the SNR drops below about 20dB the BER increases. At some point the errors are too large to resolve so the data rate must be lowered or a threshold will be crossed and the signal is unusable thus the 'connection' is dropped.
When the SNR is greater than ~20dB the more useable or stable the signal becomes.

Based on data reported here by spectrum analysis it appears the 'hack' has enabled spectrum below and beyond the WLAN band. This moves the LB carriers away from the more congested part of the spectrum. The less 'crowded' the greater the SNR is likely to be which leads to better BER and this is seen as 'range'.

This is a oversimplification to make a point. If anyone can offer more insight please do as I welcome the discourse.

So...
More Channels = Better Range

Now, what I seem to notice is that even though there are more channels available the Auto setting will only select from the 13 - 20 range and anything above or below this will need to be selected manually. Is this correct?

 

[Oso]

So...
More Channels = Better Range

Now, what I seem to notice is that even though there are more channels available the Auto setting will only select from the 13 - 20 range and anything above or below this will need to be selected manually. Is this correct?

Yes, that is correct. You need to manually select the added channels.

 

[N017RW]

So...
More Channels = Better Range

Now, what I seem to notice is that even though there are more channels available the Auto setting will only select from the 13 - 20 range and anything above or below this will need to be selected manually. Is this correct?

No. More channels = more channels.

Shifting the band into less crowded spectrum = more 'range' as a function of signal quality.

 

[BudWalker]

......
By the rules you are still limited to 1W for telecommand under amateur radio rules. I would read the rule to limit power out from the transmit amplifier, so you would be free to increase EIRP by using high gain antennas.

I knew there would be a reason that I acquired 2 9 foot old style satellite TV parabolic antennas. I've been dragging these around through 2 moves for the last 15 years. A ham friend has a a repeater site about 13 miles from my house that I can hit on 70 cm if I stand on the hill next to my house. The path is over uninhabited areas. I'm thinking a one-way flight from his repeater using those two parabolics could be possible.

 

[43k]

I ran my spectrum analyzer before I installed the channel hack and then afterwards. The hack does not change DJI channels 13 to 20, it just adds more channels above and below the original 8.

The channels are 8 mHz wide with 2mHz spacing. The center frequency of a DJI channel is Fc = 2286 + (channel# -1) *10
the lower frequency is Fl = 2282 + (channel# -1) *10
the upper frequency Fu = 2290 + (channel# -1) *10
E.g DJI channel 7 spans 2342 mHz to 2350 mHz, DJI channel 32 spans 2592 mHz to 2600 mHz

DJI channels 13 to 20 are coincident with the US WiFi channels 1 to 13.

DJI channels 21 to 32 occupy 2482 mHz to 2600 mHz and are above the US WiiFi channels. I assumed that since DJI removed channels 21 to 32 it was because it was illegal to use those frequencies in the US. But now I'm not so sure. https://transition.fcc.gov/oet/spectrum/table/fcctable.pdf seems to indicate those frequencies are available for ISM use. It'd be good if others could interpret what that document says about those frequencies.

Thank you, very good confirmation.
It matches and confirms the channel table I posted in a previous post.

As I understand it, the distance between channels thus are 10 MHz, the used bandwidth is 8MHz per channel, and the unused bandwidth between channels is 2 MHz, correct?

 

[N017RW]

If I understand and assuming the freqs. measured are center, then the BW is +/- 5MHz on each side of center.

 

[BudWalker]

As I understand it, the distance between channels thus are 10 MHz, the used bandwidth is 8MHz per channel, and the unused bandwidth between channels is 2 MHz, correct?

Correct

 

[BudWalker]

It matches and confirms the channel table I posted in a previous post.

The freqs that you have shown in your table are the upper end of the channel. Eg.channel 1 is 2282-2290 MHz

 

[N017RW]

Clearly out-of-band and contrary to the P3P/A FCC test report.

 

[Daninho]

No, I have not tried it. But I am basing my comments on engineering data, being I am an engineer.
I am not arguing that a certain channel could be less noisy for you. I am arguing, that regardless of which channel you use, if you use a clean channel , either one of the 8 or one of the 32 enabled by the hack, you should get the same result. Whichever channel you use does not, and cannot increase the range.

I see some people have started to do experiments that will prove the point.
So, I also started to think, what could, engeeringly, cause you or others to actually measure a higher range ?
The only thing I can come up with, is if the RF amplifier is not linear, and has more power at certain frequencies. If that particular frequency is the one you are using, you will get more range, as range is a function of power. As a matter of fact, for the range to double, your power would need to quadruple.

I think that as well but th thing is that my P3 and many others are limited to a certain range of around 1300m which im totally fine with if im honest but more range is always nice to have because in case of a fly away it is like a peace of mind and you can track your quad longer if its getting nuts. It would be a shame when my P3 would freak out someday and fly of its own in one direction and the video or RC connection breaks at 1300m.

So DJI must have made some changes because i saw tons of videos of P3 reaching 4000, 5000,, 6000m in CE mode. I also think that they limited the channels to 8 before they released the Phantom3. I remember the pissed inpire pilots back then but as far as i can remember the Phantom3 never had 32 channels. What could explain the 1300m limit of many P3s?

 

[43k]

An updated frequency table based on BudWalkers findings, with interference mapping:

 

[BudWalker]

Updated frequency table with interference mapping:

Very convenient. Much easier than looking at my formula and wondering if Im doing the math right.

 

[BudWalker]

I did some additional spectrum analyses. The following is a baseline with the controller turned off.

The following is with the controller running. Phantom is not turned on.

The results seem to be independent of the channel chosen. I tried channels 1, 25, and 32. They all seemed about the same.

 

[hidaven]

Ok so we agree that your not getting any kind of boosted or added power but as posted, you are getting less congested channels that translates to added distance due to lower crowding of the existing stock channels. To all the engineers and analyze personnel, why is there no action on the upper channels 26-32? Are these channels as strong as the overlapping ones from 12-20 or so? And again my question is why would DJI have orig. had all of these channels working with better range at firm. 1.07 and then cut these channels out which coincided with numerous reports of signal loss and decreased distance? I get that "power" isn't increased with this hack but it is creating much less used frequencies that absolutely are translating into better distance and less drop outs.

 

[Daninho]

I did some additional spectrum analyses. The following is a baseline with the controller turned off.View attachment 27203 The following is with the controller running. Phantom is not turned on.View attachment 27204The results seem to be independent of the channel chosen. I tried channels 1, 25, and 32. They all seemed about the same.

So does that mean the "hack" is just a hoax and its mostly placebo effect going on here? Maybe it is only displayed in the app that you have 32 channels but not in the quad or remote controller FW and thats why it still uses the same 8 channels than before but just the app says 32?

 

[43k]

I did some additional spectrum analyses. The following is a baseline with the controller turned off.View attachment 27203 The following is with the controller running. Phantom is not turned on.View attachment 27204The results seem to be independent of the channel chosen. I tried channels 1, 25, and 32. They all seemed about the same.

Really cool, what kind of equipment is that?

 

[louforgiveno]

This is being way over-thought. No this does not increase power, but it seems that if you are running stock channels (without the hack) in a wifi congested area your fpv range will suffer, but running the hack you can get on a clean channel thus giving you back fpv range that otherwise might be compromised. So let's all take the term "increased range" add in a touch of common sense and celebrate the fact the option at least exists.

 

[hidaven]

It's NOT a hoax. Channel 30-32 are showing way less activity and get me notably further than any of the channels DJI is giving us stock. So unless my increased range is explained by some other unknown phenomena, these less crowded channels are in fact doing something.