1
\$\begingroup\$

I have been working with NRF modules for some time now. I have been using the 100m rang version as shown here.

enter image description here

They are working great but I want to increase the range, so I have bought the PA + LNA version of the modulue.

enter image description here

I have the receiving NRF module on a drone and the SMA connector and the included antenna is quite heavy and weighs it down to one side.

I would like to decrease the weight of the larger module as much as possible, and have seen some antennas that seem like small strands of wire. Is it possible for me to just desolderer the SMA connector and solder on a "wire antenna" directly?

If I were to replace the antenna and connector of the module, what do I want to look for when getting a good light weight antenna?

\$\endgroup\$

1 Answer 1

0
\$\begingroup\$

Good news: Yes, you can get rid of the SMA connector and the antenna.

Then you can use a chip type antenna or just a piece of wire with the right length.

But you will have to match this new antenna to 50 Ohms for best performance. This was done with the 3 small SMT caps that you see on the picture right before the SMA. You will have to find new matching values and this is done with a VNA network analyzer. But if you can live with a few (like 3-6) dB loss, you might get away without matching and just connect your new antenna right to the PA.

Edit: Ok, i got from the datasheet that operating frequency is 2.4GHz. This calls for a lambda/4 monopole antenna which is 3cm long (standing 3cm rectangular to the GND plane). Such an antenna has a (real!) impedance of 36 Ohms, so you won‘t loose much of power if you do not provide the right matching elements.

\$\endgroup\$
6
  • \$\begingroup\$ There is not typically a sufficient ground plane in such a setting, so a dipole (often folded) is more commonly used. \$\endgroup\$ Jun 4, 2018 at 20:59
  • \$\begingroup\$ @ChrisStratton Yes, I agree. But also a dipole is hard to do. I think an inverted F antenna would be best here. You could just cut and reuse the one from the board without PA. \$\endgroup\$ Jun 5, 2018 at 5:13
  • \$\begingroup\$ Your claims are quite ignorant. A dipole is by far the simplest antenna to execute, and the one most commonly chosen for this application in the real world when performance is desired. Something like an inverted F is far more complex in proper execution - it is typically chosen as a compromise for mass production cost (etched on PCB) or space constraints, but not for effectiveness. \$\endgroup\$ Jun 5, 2018 at 5:53
  • \$\begingroup\$ @ChrisStratton English is not my native language, so I might have taken the wrong words, sorry. What I meant is that a dipole needs a balanced feeding and the inverted F is just simpler to tune. \$\endgroup\$ Jun 5, 2018 at 5:55
  • \$\begingroup\$ False and false. An inverted F is far more dependent on execution details, and therefore harder to tune. And no, a dipole does not require balanced feed - that's just about classic misconception #1. \$\endgroup\$ Jun 5, 2018 at 5:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.