nrf24+ module with stick antenna

[ben999]

Hi Guys,

I would like to connect a stick antenna to a basic nrf24L01+ module.

Please note that i do not need any additional range.

The reason i'm asking is because the nrf is surrounded by metal, copper traces and battery...

So getting the antenna out of the housing might help.

I have an SMA connector handy and a stick antenna as well.

My main question is about soldering the coax cable :

1 -shall i cut the trace as stated in numerous hacksites ?
2 - shall i solder the inner conductor where the blue arrow is ?
3 - shall i solder the outer connector (shield?) where the red arrow is ? or is it best to scratch underside of board and solder straight into ground plane ? but then that reveals more inner connector length, thus next question...

What is the importance of the length of "naked" inner conductor where the insulation will be cut ?

Thanks a lot for your help, comments of any sort are welcome

[NeverDie]

@ben999 said in nrf24+ module with stick antenna:

Please note that i do not need any additional range.

Please don't take this the wrong way, but have you ever heard the phrase "If it's not broken.... "?

That being said, if you want to do it anyway... you'll want to consider impedance matching and probably want a VNA to check your work. i.e. it immediately gets very complicated. If none of that matters, then I guess how you execute it doesn't really matter either: there's just GND and ANTENNA to wire up. GND goes to the outside, and ANT goes in the center. If it's not a dipole antenna, then maybe only just the ANT connection will matter. Just be aware that you might be worse off than before you began.

If, on the other hand, you wanted to add a wire-whip antenna instead, then you could theoretically start-off long and then trim the length down to tune it better.

I wish there were an easier way, but, AFAIK, almost nothing about antennas is straightforward if you want to do it better than what you already have.

[ben999]

@NeverDie thanks a lot for taking so much time for your answer

Your explainations pushed my thinking a bit further. I now understand that i can't just solder a 2.4ghz stick antenna in-lieu of a "trace" antenna just because it is a 2.4ghz board... am i right ?

The main reason for my post is that i need to have a remote antenna.
And i also wanted to keep clear of Power Amplified modules as their power consumption is too high for my needs (tiny LiPo and solr panel)

And i also wanted to use what's in the drawer

I shall then turn to nrf modules with external antenna. Usual one are difficult to get now. But it seems there are newer ones out there (at least their layout seems new to me) :

Anyone tried yet ?

Anyway, thanks a lot for making things clearer

[skywatch]

@ben999 You may not gain much by doing this and things could even get worse.

But if you want to try then I suggest removing the component to the left of the blue arrow and then attaching some micro co-ax centre conductor to the left hand pad where the component has been removed (as we see it in the photo) and the screen going to the closest ground point.

[ben999]

@skywatch oh great thanks for that !

by removing the smd then the signal becomes "compatible" with a 2.4ghz stick antenna ?

or shall i go with wire and adjust length ?

Thanks everyone

[skywatch]

@ben999 said in nrf24+ module with stick antenna:

@skywatch oh great thanks for that !

by removing the smd then the signal becomes "compatible" with a 2.4ghz stick antenna ?

It completely removes the strip antenna on the pcb as well as the matching stub. The component is likely a zero ohm resistor. So you will be taking the RF from the point before the antenna and it should work.

or shall i go with wire and adjust length ?

That is up to you! You could always try both and see what works best for you. It's only a few minutes work. Don't forget to post your findings for others to learn from...

[OldSurferDude]

@ben999 @NeverDie

I had found a similar article about making the antenna a dipole. The interesting thing the article stressed was the lengths of the wires. I'm not an antenna engineer (my brother is) so I made the wires as suggested. I think it made a small improvement. and I still use that radio.

My advice on antennas is: don't modify it. If your application needs more range, you're going to need more power. Signal strength drops off with the cube of the distance. So you're going to need a better antenna. For $3 (and a month or two delivery time) you can get a theoretically better module+antenna