Micro 4 inch - Apex clone

By skydiverfpv on Feb 26, 2022

6  444  2


This is my first 4 inch micro build. The frame used is steel4 from banggood (a clone of micro apex 4). Wanted a durable frame and this is the one that I could get hold of. Motors are Eco II 2004 3000kv from Emax. A Chriss Rosser video on the same made me decide on this. I had a spare caddx vista unit with dji camera and is the one used in this build as video system. The electronics - FC (Aikon f7 mini) and ESC (Diatone Mamba F30 mini) are from another 2 inch micro quad that I had (these electronics were an overkill for the 2 inch). For propellers, there are not many choices and Gemfan Hurricane 4023 is the only one that was available with a t-mount. For battery I chose Tattu Rline 1050mah 4s 95c for a longer flight time.

Alt Tag

Build Highlights

  • The frame feels sturdy and the carbon is of decent quality, however was not of the best finish. Had to chamfer the sharp edges. A small file comes bundled with the frame and that will do for the job. I dipped the frame in water while filing to avoid inhaling any of that fine carbon dust.

Alt Tag

  • The camera plate does not fit well out of the box. Required some filing to get that fitted into the top and bottom plates.
  • The arms fit perfectly in the sandwiched design between two bottom plates. Once secured with screws, no wiggles and feels very sturdy.

Alt Tag
Alt Tag

  • The screws for the standoff are of M2.5, not the standard regular M2 or M3. Care must be taken not to lose it. May not be easy to get the same specs screws.
  • The FC-ESC stack required M2 screws and the M2 screws were a bit wobbly with the bottom plate. Added a silicone o-ring to get that firm in place (see the picture).

Alt Tag

  • The ESC is mounted with its battery lead and capacitor facing towards the front of the quad. This is because, when the vista unit is mounted, there is no space for the capacitor between the front and back stacks. This altered alignment required a remap of the motor resources in betaflight CLI.

Alt Tag

  • FC port is aligned properly with the ESC port for the FC-ESC connection, so no change required in the FC orientation. It stays default.
  • Though the FC has a dedicated DJI quick connection port, it comes on the sides and the wires were protruding out when it was connected. It didn't feel very durable and I did not want those wires to go lose and come between the propellers in mid flight. So the quick port is not used, vista wires are directly soldered to the FC.

Alt Tag

  • FC comes with a 10V/1.5A regulator which comes very handy for DJI. Vista unit is soldered to the FC 10V pad instead of soldering directly to the battery pads (VCC). Refer wiring diagram below.
  • Used foam landing pads to reduce scratches on the bottom plate during landing.
  • Happy Model EP1 receiver is used with the smaller length antenna (it comes with two lengths to cater to different builds). It is wrapped in a clear heat shrink and mounted on top of the vista unit with a double sided tape. I would have preferred to wrap the Rx in kepton tape considering the heat vista unit could generate (may be for later). A cable tie is also used to secure the vista unit, the receiver and the wires together.
  • Battery leads are secured to the middle standoff using a cable tie to avoid the tension on the ESC pads during battery removal (or crash).
  • The capacitor is slightly bent towards the bottom and a thick double sided tape is kept between the bottom plate and the capacitor to hold it firm in place. Besides the camera comes just on top of the capacitor which avoids it from moving around and breaking the leads in the long run.
  • Battery pad that comes bundled with the frame fits nicely with the cuts and edges aligned to the top plate.
  • Receiver antenna is mounted on the back edge of the bottom place using a cable tie. Did not use the tpu antenna mount that came with the frame (that's suitable for a 900MHZ antenna like crossfire or R9M).

Alt Tag

  • A caddx antenna mount is used to secure the video tx antenna to the tpu part at the back of the quad. The antenna tube is thinner than the mount, so used two heat shrinks one on top of the other to increase the diameter of the tube where it is secured with the mount.

Alt Tag

  • A heat shrink (blue) is used on the vtx antenna cap to improve the durability ( i have prior experience where the antenna cap easily comes off during a crash, this technique prevents that from happening).
  • The frame also comes with a gopro mount, haven't used it on this build yet.
  • Motors come with 2 sets of screws for mounting - M2 6mm and 8mm. Use 8mm when the tpu arm guard is used, otherwise 6mm should do.
  • The propeller T mount is secured with the screws that come with the motors (i think it is 9mm M2).
  • Dry Weight : 234gm
  • AUW with R-Line 1050mah 4S battery : 355gm

Wiring Diagram
Alt Tag


  • PID tune so far is the default betaflight 4.2 tune. Will update here when that gets changed.
  • ESC is blheli_S flashed with bluejay firmware.

Alt Tag

  • Motor resources are remapped to match the current orientation of the ESC

Alt Tag

  • In the ports tab
    • UART2 is enabled for Serial Rx (HM EP1 is soldered to T2 and R2 pads)
    • UART5 is enabled for Config/MSP - T5/R5 pads are soldered to Vista unit.

Alt Tag

  • Enabled Bidirectional DShot and rpm filtering

Alt Tag

  • Rates are changed to my usual "actual" rates.

Alt Tag

  • Filters are at betaflight default. No change so far.

Alt Tag

  • On the receiver tab, mode is set to serial based receiver, and the provider is selected as CRSF. Aux12 is set as RSSI channel (used to get the rssi value on OSD).

Alt Tag

  • Enabled OSDs are - Battery Average Cell Voltage, Battery Voltage & RSSI Value

Alt Tag

  • Maximum arm angle is disabled (set to 180 deg) in the config tab.

Alt Tag

  • Display and OSDs are enabled in the features section of the configuration

Alt Tag

  • Modes tab mapping is as given below.

Alt Tag


Part List


STEELE 3 154mm 3 Inch / STEELE 4 178mm Wheelbase 4 Inch Carbon Fiber Frame Kit 4mm Arm Thickness Support Vista Air Unit for RC D
See Site

Flight Controller

Aikon Electronics F7 Mini V2 MPU6000 MINI FC W/OSD Flight Controller For DJI FPV Air Unit FPV Multi Rotor Part
See Site


ESC-MAMBA F30MINI 2-5s 4 in 1 BLHeli_S Dshot600 Electronic Speed Controller (2 builds)


4 x 1PC EMAX ECOII 2004 4-6S 1600KV 2000KV 2400KV / 3-6S 3000KV Brushless Motor for FPV RC Racing Drone
See Site


GEMFAN Hurricane 4023 3-BLADE 4" Durable PROP 2CW 2CCW (CHOOSE COLOR) (8 builds)

FPV Camera

Caddx DJI Digital HD FPV Camera (163 builds)
See Site

FPV Transmitter

Caddx Vista Unit for DJI Digital HD FPV (No Camera) (92 builds)
See Site


Polar Antenna for Vista (20 builds)


HappyModel 2.4GHz EP1 RX Express LRS Receiver (73 builds)


Tattu R-Line 1050mAh 95C 4S1P Lipo Battery Pack with XT60 Plug (2 builds)


RadioMaster TX16S Hall Sensor Gimbals 2.4G 16CH Multi-protocol RF System OpenTX Mode2 Transmitter for RC Drone (82 builds)


DJI FPV Goggles V2 (169 builds)
See Site

Misc Parts

Caddx/True RC Singularity/Albatross Antenna Mount

Radio Module

Happymodel ES24TX 2,4 GHz ExpressLRS ELRS s dlhým dosahom, nízkou latenciou a vysokým opätovným blikaním modulu Micro TX p (6 builds)

Battery Charger

ToolkitRC M8S 400W 18A Charger

Soldering Iron

Sequre SQ-D60B MINI Soldering Iron w/ TS-B2 or TS-D24 Tip (2 builds)
Show stores (10)


Sign in to comment

KM|fpv   9 days ago  

Nice build.
Why did your enable "DISPLAY" in configuration, did your attach any oled screen?

skydiverfpv   7 days ago 

no oled display. i think that's a mistake, i had some trouble with osd with dji, so would have gone and switched on anything related to osd and display... 😀
will correct the write up soon. thanks for pointing out.

Guides & Reviews

Jun 21, 2021

AirbladeUAV has done it again and this time they've brought long range to the 5" class! Based on the popular Transformer Mini, the new Transformer 5" Ultralight adopts a lot of the same design philosophies with larger props and more payload capacity. It can fly upwards of 20 minutes on a 4 cell Li-Ion battery pack and in ideal conditions it's got a range of over 4 to 5 miles. In this guide I'll walk..

Read more
Mar 04, 2021

With the release of the DJI FPV Drone cinematic FPV has become a lot more accessible, but you certainly don't want to crash a $750 drone! The QAV-CINE Freybott is a compact, lightweight cinematic FPV drone that can take a hit and keep going. It's a lot safer to fly indoors and around people. With a naked GoPro or the SMO 4k you can capture some great stabilized footage. In this guide I'll show you..

Read more