Bluetooth radio frequencies
WILL interfere with the operation of the Spark, even though the Spark itself does not use Bluetooth.
Especially when flying without an OTG cable as the WiFi connection between the device and the RC is more vulnerable to a disruption.
There have been
numerous posts about that.
I"d like to see your RF analysis that shows Bluetooth WILL interfere with a WiFi connection. Unless a complete moron designed the WiFi receiver in the spark (and that's unlikely but possible) AND you are OPERATING IN A CROWDED WiFi area AND you are operating AT 2.4Ghz (vs. 5Ghz), it's virtually impossible for Bluetooth which is very low power, spread spectrum to interfere with WiFi which is multi-channel much higher power. Otherwise your phone, your computer, your car electronics, etc. would never work.
IF you are operating in an area that has a LOT of other WiFi sources AND you are operating at 2.4Ghz AND there are so many WIFI sources that YOUR SPARK CANNOT find a clear channel AND you have your phone Bluetooth ON and ACTIVE , it could contribute to the INTERFERENCE you are getting that is MOSTLY attributable to other WIFI sources because then BLUETOOTH is also trying to FIND a clear channels and can't because THEY are ALL CLOGGED. IF there are many WIFI transmitters around then BLUETOOTH searching for free frequency hopping channels will become noise and raise the RF noise floor. This should NEVER happen if you are a safe DISTANCE from other WIFI sources OR you operate at 5Ghz. There should BE PLENTY of clear FREQUENCIES for both WiFI and BLUETOOTH if you are in open areas, because this is how they were designed to WORK. Designed FOR cohabitation.
TECHNICAL explanation FOLLOWS.
BLUETOOTH uses Frequency Isolation: Adaptive Frequency Hopping (AFH) is a built-in coexistence feature that is found in most Bluetooth devices today (vs. Direct Sequence Spread Spectrum (DSSS) which is used by WiFi). With AFH, a Bluetooth radio scans the operating band for interference and adapts its frequency hopping patterns to avoid DSSS channels (used BY WIFI).
This decreases interference (and therefore increases performance) between Bluetooth and Wi-Fi radios.
ADDITIONALLY: Today's PROPERLY designed phones and tablets use Time Division Multiplexing (TDM) as a coexistence method where Bluetooth and Wi-Fi radios (embedded in the same device and linked together with input/output signaling pins or “wires”) take turns transmitting. An output wire is asserted by a radio when transmitting to indicate to the device on the corresponding input wire that it should refrain from transmitting during this time. TDM can be implemented between separate Bluetooth and Wi-Fi chips by linking them together via a printed circuit board. With increasingly popular combination Bluetooth/Wi-Fi chips, TDM is implemented within the same chip and therefore arbitrates between the two interfaces quickly. Poorly designed or MUCH OLDER phones and tablets may not have this but certainly all Apple and other major phone brands will have it.
Therefore, your phone/tablet to RC link should be far more reliable than your RC to drone link. That RC to drone link is operating at the margins of performance when the drone is at some distance and anything that blocks line of sight or another WIFI that transmits on the channel you are using could disrupt your connection.
However, none of this applies if DJI did something really stupid in their control apps or firmware.
