Hi,
I’m new to this forum so please forgive any ‘errors’ part.
I have a pair of 2.4Ghz modules (A/V sender type) that I wish to make a board for. They have half pitch (1.27mm/0.05") headers for all connections including the ‘RF out’. So, if I was to connect a header socket, to an SMA connector (namely, the type on the sparkfun website) I assume there will be restrictions of the width of trace used, for impedence matching purposes (50ohm). Because the header socket used, is so small (again, 1.27mm) a ‘wide’ track widht is not possible, as this would spill over to the two outer pins, which are grounded.
This is really bugging me, I have no RF design experience, and I don’t want to get a board made up, only to find I’m losing 20dB from the module to the antenna 
I’m planning on using Olimex, so the board will be FR4, 1.6mm, double sided, I’ve got a ground plane on both top and bottom layers (design habit). The distance beween the module connector and SMA connector only really needs to be a few mm, so I was kinda hoping I could get away with any old trace width.
Also, is there any need to seperate RF GND, from the circuit GND?
Sorry for a long post, I hope someone with more RF experience than I can give some advice, its holding up my design 
Thankyou,
BuriedCode.
If it is only a few mm to the RF connector it probably doesn’t matter very much, as that distance will be very small compared to the wavelength, even at 2.4 GHz.
You could always put a via close to the connector pin connecting to a wide track over a ground plane giving 50 ohms. Or, use one of those tiny Hirose 50 ohm connectors - lots of RF modules use them. They are available with an SMA female connector on the other end. I’ve got a couple here for the Siemen MC55 GSM modules I’m using.
Leon
leon,
Thanks for your reply!
Its good to know I can sort of get away with a small trace. Oh and I simply didn’t realise about using a ‘via’ to route a microstrip on the underside of the board, it’ll still have a ground plane on the opposite side of the board, so i guess its perfect!
Or, use one of those tiny Hirose 50 ohm connectors
I googled them, they really are tiny aren’t they…I might try and get hold of some. Although, I don’t have really strict rules on PCB size, just the smaller the better really, seeing as how the modules I have are tiny (50x30x5mm I think) would be nice to make a small board for them.
This board I’m making is really just a ‘breakout’ board, since I’m going to be using these modules not only for analogue A/V, but also experimenting with data as well… at least until I get my hands on some of those MiRF boards (my app has a datarate of 1.5-2MB/s).
Thanks once again, good to know this board (and the members) exist
BuriedCode.