Mi Repeater 2 moded

Stele · Jan 2, 2019

Hello,

First if all the following mod was not my idea. A user here in the forum did it first, but unfortunately never followed up with results. So I did it my self.

First I cut open the housing.
Fortunately you can disconnect the stock pcb-antennas simply by removing two solderbridges (shown in the red circles)

After that I soldered two 2.4 ghz Wi-Fi antennas from an old accesspoint to the convenient placed soldering pads on the back of the pcb.

After that I've reassembled the housing and taped the antennas to it for now. Later on I'm planning to print a new enclosure which contains the repeater and a powerbank.

At the moment I'm only capable of doing indoor tests because of wind and rain.
But it looks promising, in areas where my reception before dropped to 70 dB now it stays at solid 90 dB.
As soon as possible I'll follow up with an outdoor test.

Regards Stele

Flydrone · Jan 2, 2019

Very interesting change ... a short time ago, I was thinking of doing something similar, but then I left everything original.

Stele · Jan 2, 2019

Flydrone said:
Very interesting change ... a short time ago, I was thinking of doing something similar, but then I left everything original.

I had to give it a try. Its´s such a simple mod and easy reversable.
Depending on how good it performes I´ll switch the antennas for patch or high gain ones

Flydrone · Jan 2, 2019

Keep up to date on the tests you will do with Tello!
Greetings.

ChazBarros · Jan 2, 2019

Cant wait for the results. I expect at least a sightly range increase.

raulvolador · Jan 2, 2019

Opss...

I'm working the same concept.

I'm glad to share with you my own Xiaomi WIFI Extender mod. I use WIFI RP-SMA pigtails. That way I can easily plug/unplug different kind of 2.4 Ghz antennas.

All assambled into a cardboard box.

First test outdoor where very promising.

xiaomi wifi external antennas cardboard box.jpg

Stele · Jan 2, 2019

Great, more people trying to improve it.
I´ve tought about pigtails but didnt want to spend money before I don´t know that it works.

Have you done a max range test so far?

WalterH · Jan 2, 2019

Stele wrote “But it looks promising, in areas where my reception before dropped to 70 dB now it stays at solid 90 dB.”.
Maybe I am wrong, but I thought that Wi-Fi signal with lower dB was better than higher dB, or is that with just a cell phone signal?

SleepyRobo · Jan 2, 2019

@WalterH your correct I was going to mention this as well, a lower db for wifi means a stronger signal, usually a negative db. Closer it is to zero the stronger it is. What people don't understand is that a transmitter can only transmit so much watts. so modding and putting bigger antennas on will not give you bigger range.

Also I talked to Ryze support and the Tello uses a smart switching dual antennas with 2 little patch antennas in the back feet. Smart switching is nothing knew, but a drone with smart switching of this size is unheard of. This feature allows the drone to switch antennas for transmitting the WiFi db signal to the better antenna facing the phone. But that causes video lag too especially since they are patch antennas in the feet of the drone.

A rule of thumb is you don't mix dipole and patch antennas.

His db probably went to and stayed consistently at 90db instead of 70 due to the fact that the extender now has to run at Max watts just to maintain a signal with those dipole antennas which throw out a signal in a dome shape bubble, where as the old oem patch antenna used a concentrated calibrated pie shape transmission and reception.

SleepyRobo · Jan 2, 2019

Side note Tello was designed for selfie shots so the antennas are best used with camera facing your phone.

Stele · Jan 2, 2019

WalterH said:
Stele wrote “But it looks promising, in areas where my reception before dropped to 70 dB now it stays at solid 90 dB.”.
Maybe I am wrong, but I thought that Wi-Fi signal with lower dB was better than higher dB, or is that with just a cell phone signal?

You are most likely right.
I use the tellofpv app which showeds the reception in positive dB which is decreasing as further the drone gets away.

Stele · Jan 2, 2019

So I've managed to fly outdoors in calm 5 minutes.
Unfortunately in a residential area with 53 2.4ghz networks around. So heavy interference.
I've got 113m (according to tellofpv) until it got to fragmented to fly comfortably in an area with cars and people underneath (I know not good).
Up to about 90m the video feed was good with next to no dropped frames or fragments.
I'll try to do a second test in a more remote area.

WalterH · Jan 2, 2019

SleepyRobo said:
@WalterH
SleepyRobo said: Also I talked to Ryze support and the Tello uses a smart switching dual antennas with 2 little patch antennas in the back feet.

Thanks for post. Was not aware that Tello uses smart switching dual patch antenna. Lot of technology packed into this little guy.

Stele · Jan 9, 2019

I've tinkered even more and build a set of antennas.

They are called moxon antenna and are directional ( round about 90-120 degrees)
Once again I can't test outside but the inside test are very good.

Stele · Jan 10, 2019

My frankenstein moxons seem to work good. so I decided to build a second proper version. the 3D print will be done tomorrow.

when they prove to work good, I´ll share the STL of course

raulvolador · Jan 10, 2019

I'm working too into a harder enclosure for my "pigtail" Xiaomi repeater mod. Cardboard is not the best support for testing antennas

I hope I can perform better tests when finished.

raul

volate!lo · Jan 10, 2019

Stele said:
You are most likely right.
I use the tellofpv app which showeds the reception in positive dB which is decreasing as further the drone gets away.

Both of you are right but you are not talking about the same thing.
Absolute signal strength in dbm doesn't help. If I stand beside you in the office and shout you in the ear I bet you notice its a strong signal. If I do that same while we are standing in the first line at WOA Wacken the result is different. My signal strength is just the same but barely makes it through the music. The "signal to noise" ratio isn't good.

Tello does not report absolute signal strength in dbm but the "Signal to Noise Ratio" or SNR in db. SNR defines how clearly the signal stands out from the noise around it.
Tello reports this in a low granularity: 90,70,40,10 are the values I have seen IIRC. 90db is excellent, 10db is marginally and about to drop the link.

Excerpt from wikipedio on SNR:
Signal-to-noise ratio (abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise.