It could be a failed firmware flash. Please try to flash the RF firmware for the air unit.
Here is the firmware link: https://drive.google.com/drive/folders/1CuaIkqK7feOsAzeWUXoySw-Lo5eXUlHX?usp=sharing
Very weird. Since I didnât tried to flash anything. So, there is nothing to fail.
Can you give a brief instruction how to do a flashing ? In should be done with SIYI PC Assistance. Right ?
Yes, it can be done with PC Assistant.
By the way, when did you order and receive this unit? May I have some order information, please?
Frank Wang - Thank you a lot! Yes flashing helped! But still not clear why this fail happened. Since there was no changes in Air Unit from my side.
Have a question:
What firmware is the latest - 5.X.X or 0.X.X ? Since 0.X.X is latest by upload time
One more - telemetry input in Air Unit, itâs 5V, GND, RX ? What kind of protocol should be used to pass the data from FC ?
PS: Regarding my purchase - order was made at 22-04-15. Donât remember when I received it.
@SIYI
I just wanted to complain because the binding of 2 Airunits to one Ground Unit didnât work.
But then I remebered that Frank explained in post 511, that this will no work with Version 0.1.8.
An therefore I upgraded my system to the new Version. And that how it works.
It would be helpful for newbies to add in the Manual how to select in the Menu of the GU to get connected to the assistant. Video Mode > WiFi/Upgrade. Because a little bit strange to find it under VideoMod to transfer Data.
The associated Airunit has to select manually in the display of the GU.
Thank you Frank. 
By the way. all other links (Video by LAN, Data by Bluetooth and RC by PPM) worked immediatly
About this question, please check the below picture taken from the manual
The telemetry port on HM30 air unit and all other SIYI systems are UART port. Please check the below picture for pin-outs detail.
Mavlink protocol is used in almost all SIYI systems for telemetry.
Glad to know that you get binding to multiple air units worked.
It is related to the Type-C port, if it is occupied for video stream, then it cannot be used to connect PC Assistant.
Thanks for your suggestion, it is indeed very necessary to add this note in the manual to remind customers of checking the configuration of the Type-C port if they cannot connect to PC assistant.
thanks Frank I didnât see the answer.
I was wondering if the relay function is implemented yet? I have a bathymetry boat thatâs rarely line of sight lol.
Ah, I see that it is with the HM30 Dual Link Combo. But what does that include? Itâs pretty confusing looking at the different sites. Some show two HM30 units, others show a MK15 transmitter and a HM30. Canât find any detailed description of whatâs included. Price is all the same though lol.
Hi @SIYI I am going to re-attempt my 36km mission some time in the next month or so, using these 23db patch antennas. Please confirm if you recommend this. As a reminder, I went 22.6km with the Maple Wireless 17db patches
Are you using the âFlymydreamâ tracker? Pretty stupid name, but Iâve got one collecting dust lol.
The relay function is ready and it comes with the dual link combo only.
You can refer to the MK15 manual temporarily for the detail feature. It will be updated to HM30 manual very soon.
https://drive.google.com/file/d/1Ux-pSB-r36VDyioDd2M0fbhDwckk5YaF/view?usp=sharing
We never tested this antenna. Please try to judge by your professional knowledge.
If you need an option from SIYI, we ever tested a 26 dB antenna and it worked well far to 60 km.
So the HM30 Dual link includes a MK15 tx? So if I have the MK15 at my launch site and the HM30 at a remote location with line of sight to my MK15, if I lose connection from the mk15 to the air unit but have los from the air unit to the HM30 the MK15 will transmit/receive to the HM30? Like a radio relayđ Sorry for the crazy run on sentences!
This is how the RC Relay feature works in SIYI system.
There are three available combos for this purpose so far.
- MK15 Dual Remote Combo
- HM30 Dual Link Combo
- MK15-HM30 Dual Link Combo
After upgrading to 0.1.8 the Videolink Quality on the tablet is much better.
Is this a âhiddenâ feature? 
Packing List of MK15 Dual Remote Combo
Packing List of HM30 Dual Link Combo
Must be true 
what about fcc? is this product ok to use in north america for example?