The nRF was a useless inclusion tbh, sorry for the confusion. The nRF already has an smd antenna.

The thing with those antennas is the size of the antenna vs the size of the module, it's almost twice the size, negating any benefit of having such a small module.

Hence my desire to use an SMD antenna on a small board instead.

antenna design is usually limited by one of these things: size, gain/radiation pattern, efficiency, bandwidth (fixed here, entire 2.4ghz band)

you can probably use off the shelf antennas used for drones if these are small enough for your application

soldering coax can be tricky, don't melt center insulation. you'll need to size microstrip line so that it'll have impedance 50 ohms as well https://www.pasternack.com/t-calculator-microstrip.aspx

Thank you for your detailed reply, I really appreciate it. It answers my question and raises a whole bunch more :D, I think I need to brush up on general RF and get a better understanding of how it actually works. I shall do some youtubing and reading on it. I found a really good pdf that discussed antenna design but a lot of it I didn't understand, so I'm going to need to learn a bit more.

Ill also take a look at the drone antennas too.

Thanks again for your help.

I.. Don't actually know, I've just cobbled together information over the years. My dad worked in an electronics workshop but never taught me anything. There's a good intro to electronics course on udemy and if you're serious about it, try get the book The Art of Electronics, its like an electronics bible.

i don't know what are you looking for so i'm just gonna drop some resources that i've used:

starter: https://www.antenna-theory.com/antennas/main.php

more comprehensive: https://www.microwaves101.com/encyclopedias

and on top of that, various amateur radio pages, some are indexed in dxzone.com

there seem to be two hard limits on antennas in general. one is for approx lossless antennas that are large compared to wavelength: gain, beamwidth and size are related through diffractive limit https://en.wikipedia.org/wiki/Diffraction-limited_system it's really about capture area, which is intuitive for things like parabolic reflectors, but for things like yagi antennas there's some defined capture area that ultimately depends on their length

the other one is on non-directional antennas that are small compared to wavelength. basically one good antenna that you can make is halfwave dipole, you can try various trickery to make it smaller, but this comes at a cost of either smaller bandwidth or increased losses, or both to lesser degree. it might make sense to make an antenna with 70% efficiency which is 3x smaller for example. it all depends on precise requirements

at the end of the day the most important material in any antenna are tradeoffs