search

skuep / AIOC

Ham Radio All-in-one-Cable
MIT License
764 stars 60 forks source link

USB EMI Suggestion #88

Open stretchkerr opened 1 month ago

stretchkerr commented 1 month ago

Regarding the EMI being induced on the USB cable, have you considered swapping the positions of the 2.5mm and 3.5mm jacks, so the USB port as at the bottom of the board, and the USB cable faces down, away from the antenna?

Tymek commented 1 month ago

Hello, SP5CMD here. I organized a group buy in 🇵🇱, and I got some feedback. USB interference was common. It can be mitigated with higher quality cables. This is because if you're not holding a handheld radio, with an unbalanced antenna, your cable will become a counterpoise. In this situation chokes on cables help.

My sources:

What I will try, is attaching AIOC close to the source. Maybe for v2 we should have a male USB-C option?

image

skuep commented 1 month ago

Sorry for the late reply...

In the past there have been some suggestions to "turn around" the AIOC so that the USB cable points downwards. I checked and the effort for re-routing the PCB would have been big unfortunately. I am also not convinced that this helps the EMI issues.

I think the issue is exactly what @Tymek describes but I have not yet found a neat solution for the problem (mainly due to low feedback from others and I don't have any EMI issues myself unfortunately). I was wondering whether a ferrite core on the USB lead is enough to stop the counter-poise current running along the USB cable shield but others didn't have great success. I suspect that the current still runs around the AIOC circuit board wreaking havoc (e.g. on the USB lines).

Other than that, I was thinking to add SMD ferrites to (some of) the signal lines going to the radio but I am so far not sure, which ones and whether it needs to be a common-mode ferrite (like in @Tymek picture) or if several separate ferrites would work too.

So all in all, it's currently inconclusive from my side on what to do about it.