Medium Range Five-inch

By truckz on Jan 25, 2024

6  0  5

Not a full build per se. More of a series of mods. I hope that's allowed.

This one started as a Geprc Mark5 DC 6S ELRS BNF I got for my birthday. It flies amazing out of the box. Geprc does a really great job with their build quality and tuning.

Adding an M10 GPS module was easy and gave me confidence to push the range further than before. I got the matching green TPU GPS mount that goes on the rear.

After reaching about 2.5km out, it became evident that a longer VTX antenna would be required as the battery was blocking it on every return home. So, the stock O3 antenna was replaced with a long AXII Duality.

I found the ETHIX S5 props to be very smooth and somewhat efficient but I would also like to test some biblade props in the future. I got a set of bi-blades but never got a chance to flight test them, as one broke while putting them on. So, I'm back to tri-blades.

There is a huge space at the front of the craft for a powered buzzer. So, I removed the dinky little buzzer that comes stock and zip tied a Geprc Super Buzzer in that space. This super buzzer has the button mounted on the edge making it easier (for me anyway) to press versus the ones that have the button flat on the pcb. The other thing I really like about the super buzzer, is you can unplug the leads from the buzzer when it's on the bench (my wife and dog hate the beeps)

Shortly after installing the AXII antenna, I started having problems with the GPS. It would cut out during flight, with the OSD elements disappearing completely. Sometimes they would come back, and coincide with a burst of interference in the video feed. This was really concerning and was even happening on the bench. I ended up removing the GPS from the TPU mount and placing it at the front of the craft. I don't use a GoPro on this drone, so I shrink wrapped it and zip tied it to the carbon fibre plate above the O3 camera. Boy, what a difference that made! Not only did it fix the GPS cutting out, but now I can lock onto 10 sats indoors! This is a huge improvement overall - it locks onto more satellites, quicker, and holds onto them the whole flight. I can only guess that the new antenna is either poorly shielded and/or higher gain than the stock and was spewing video RF into the GPS.

An Auline 6s 3000mAh Li-Ion was added later for longer flight times. Here's the first flight with the new battery:

Next problem: jello in the video feed. You can see a lot of it in the tail end (~4:30) of the video above. This one took a bit to resolve and I'm not sure it's completely fixed. Since I believed in the build and tune, I started looking at the O3 camera itself. I know lots of people needed to glue the camera internals to eliminate their jello, so I gave that a try. It had no effect at all. Like the newb I am, I started changing stuff without testing after. I swapped the camera with another drone with O3. Changed props to some lightweight Gemfan SL 5125's. Reversed the prop direction. Went around the whole craft applying blue loctite and tightening everything. I ran all the motors on the bench, watching for spikes in the gyro graph, but they were all smooth. Enabled dynamic idle and tweaked a couple of the PID sliders (total hail mary - I have zero idea what I'm doing) then took it for a spin:

And the jello is mostly gone! I still see some twitching in the video that Gyroflow isn't smothing out. Minor stuff. Overall I'm happy with the build and can't wait for it to warm up so I can fly more!


Part List


GEP-MK5D O3 DeadCat Frame - GEPRC (2 builds)

Flight Controller

SPAN F722-BT-HD V2 Stack - GEPRC


4 x RCINPower AOS Supernova 2207 1980KV


HQ Ethix S5 Cinematic Prop (2CW+2CCW)


Gemfan SL 5125-3 Hurricane Prop (2 builds)


Gemfan VannyStyle 5136 Tri-Blade Prop (2CW+2CCW)

FPV Transmitter

DJI O3 Air Unit for FPV Drone, Digital Transmission System, 10km Max Range, 1080p/100fps H.265 Video Transmission, Compatible wi
See Site


Lumenier AXII Duality HD 2.4/5.8GHz Dual-Band Antenna for DJI O3
See Site


GEPRC ELRS Nano Receiver - GEPRC


2 x Auline 22.2V 6S 3000mAh 10C Li-Ion Battery - XT60


4 x Tattu R-Line 4.0 1550mAh 6S 130C Lipo XT60

Misc Parts

GEPRC Super Buzzer - GEPRC (2 builds)

Misc Parts

Ummagawd UMMAGRIP - Super Sticky Battery Pad

Misc Parts

GEP-M10 Series GPS Module - GEPRC
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ng   Mar 01, 2024  

Great flights here and very cool that you're using a li-ion on the mk5! Most of the twitchiness seems to be taking place when you're higher up and at lower throttle while descending, as Jodie noted. Considering how much wind can still be present up there on the calmest of Canmore days, not a lot you can do on that front other than trying to adjust your flight path/limit your exposure to the wind when descending. That said, the following may help:

  • I found that the TPU camera mounts on the mk5 transferred the least noise to the O3 cam when mounted snug via the 4 screws but not overtightened. Just tight enough to prevent the cam from moving up/down during flight worked best for me.
  • The mk5 comes with a decent tune out of the box but that can definetely be improved upon. Since you're switching from the stock motors to something different, even more reason to go through a full tuning process. If you haven't already, check out Chris Rosser's Betaflight tuning videos on YouTube for eliminating as much frame resonance as possible with the least amount of filtering.
Jodie Froster   Feb 21, 2024  

Great flights there, I looked at the jello you spoke about. In the first clip it's clearly happening as you descend at low throttle. In the 2nd clip it's almost completely gone, 5:12-5:18 has something that might be jello, but it might just be an artifact from encoding for youtube, so i'm not sure if it's a real indicator to evaluate. If you still see lil things like that I would say turn up your d gains a lil

truckz   Feb 21, 2024 

Thank you for your comment, Jodie. I had one of the motors go bad somehow, so had to replace them with completely different ones. I haven't had a chance to update the build yet. But, I'll keep your advice in mind. Thanks again!

Nikodemus   Jan 27, 2024  

Nice build! Practical question: how do you enclose (tags) youtube-videos on this platform?

truckz   Jan 27, 2024 

Thanks! Just paste the url to your video in the text description and it embeds automatically when you preview/publish.

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