RF cable connection to board

Hi

How do you calculate loss due to a soldered coax cable direct to the board?

I have an RG316 cable with SMA connector on one end. But I'm trying to decide if it is best to terminate both ends with RF connectors and then plug this assembly into the board, or just to solder the wire to the board (seems to be common practise with wireless routers).

Ta.

Reply to
Grumps
Loading thread data ...

The cable interconnect is more expensive, but far more serviceable.

I thought that typical loss figures came from their (each connector) data sheets.

Reply to
BlindBaby

Seems to me the relevant issues are cost and convenience. The difference in loss hardly matters and could well be of either sign. And RG316 is lossy stuff anyway.

Jeroen Belleman

Reply to
Jeroen Belleman

For the connectors they do. I was wondering about losses where the cable is soldered directly to the board.

Reply to
Grumps

Thanks. It's much cheaper to solder directly than use another connector pair. Labor costs are low where this is going to be produced.

Can you suggest another (flexible) cable that is good at 5GHz, and a compatible SMA? I found some RG316 that had about 2.5dB/m attenuation at 5gig.

Reply to
Grumps

A lot depends on how you manage the transition. If you use two thru-holes, and solder the coax inner and outer to them, you'll get a capacitive discontinuity from the pads and then an inductive bump from the coax loop. Those will be moderate effects at 5 GHz. It's better to try to make something more like an edge-launch transition. Here's a crude version, using hardline:

ftp://jjlarkin.lmi.net/BB_fast.JPG

The teflon pushed out of the end of the coax a bit when I tinned the shield, and that made my air loops a little bigger. Just that much extra distance affects matching and is quite visible on 20 GHz TDR. I didn't bother to tweak this one, because this circuit works in the 100 ps/3 GHz sort of zone.

A better transition would be a plated slot at the edge of the board, that the coax shield would fit/solder into, with the coax center conductor soldering directly into a microstrip line with no bends.

Semirigid is nice at 5 GHz.

You can learn a lot, fast, with a TDR scope and an x-acto knife.

John

Reply to
John Larkin

You can probably model it and any or all parasitic effects it carries.

I think we call it guesstimation.

Reply to
BlindBaby

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.