VM275 camera/vtx combo – Antenna mod – weight reduction from 4.0 to 2.8g !

By | February 27, 2017

When you build a tiny and lightweight indoor quadcopter, every gram counts. It is nice to see that there are very nice camera and video transmitter all in one combinations available. One example of such a nice set is the VM275 camera. It is sold under different names, most of the times you can spot a CM275 or M275 label on the PCB. For example Banggood sells those under the name: Super Mini Light AIO 5.8G 48CH 25mW VTX 520TVL 1/4 Cmos FPV Camera. There are at least two different revisions of this camera, they have a slight different pcb layout.

The unmodified camera comes with a cloverleaf antenna and weight around 4grams. You can also buy versions with a very bulky dipole whip antenna.

In this tutorial I am going to show you how to replace the original antenna with something much lighter, resulting in a total weight of only 2.8g!

Please note that this modification will probably reduce the range and you get more problems with signal reflections. The antenna will most certainly also be unmatched to the transmitter impedance and might have a very bad SWR. In the worst case this might fry the transmitter. I did this mod to at least five of those camera modules to date, I never experienced a broken vtx and the range has been proven to be more than sufficient for indoor flying.

Enough said, fire up the soldering station. Make sure to use a big soldering tip (6mm) and heat up the shield and the inner conductor at once. Do not apply to much force by trying to pull the antenna away, just heat it up evenly and it will fall apart.

When you are done it will look similar to the next picture. Note that this shows hw revision 1.1, the older version has a slightly different antenna pad layout.

Now grab some flexible wire. I prefer 32AWG silicone servo wire. It is so soft that it will simply bend in case of a crash and will never damage the circuit board pads. Solder some of this wire to the center pad:

When done, apply some hot glue to fix it to the circuit board. It is a good idea to apply the glue only on the top half. The lower section stays free of hot glue and you can easily re-solder the part in case you will ever have to replace the antenna.

Now grab a caliper and set it to 12.92mm (1/4 lambda @ 5.8GHz). Take the measurement from the board edge. The lower section is close to the ground plane and (best to my knowledge) does not contribute to the exposed antenna section.

One courageous cut and you are done: A camera vtx combo with a whopping weight of only 2.8 grams!

Enjoy!

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