Can WiFi interfere with FireWire PCI card?

Question

A year ago I upgraded my PC and replaced my motherboard with a cheap one which lacks a onboard wifi and firewire. To compensate this I've purchased a tp-link 300mbps wireless n adapter and a pci firewire.

Now I recently got back to audio recording with my FireWire audio interface and I've noticed massive audio glitches when routing audio via my audio interface when my WiFi was enabled. I have now to disconnect the WiFi to be able to properly record audio.

The drivers of both WiFi and FireWire interface are up to date. Can WiFi cause an interference on FireWire? The antennas are in deed in a close proximity to the FireWire card.

I am not sure whether it affects the FireWire cable or the card itself. I have no replacement for the FireWire cable but I would expect the cable to be of high quality as it was packed with my audio interface (~800€).

The old configuration used LAN and everything was on board anyway, so I have never noticed such issues there.

Answer 1

This does indeed sound as if your Wi-Fi transceiver is interfering with your FireWire interface. However, I doubt that you’re getting noticeable crosstalk on your audio cable – this is digital audio, after all; I think it’s much more likely that the PCI cards themselves are improperly shielded, causing crosstalk between circuitry on the two cards. This would jibe with your previous experience, assuming your old hardware was shielded correctly. To see if this is the case, orient the antenna orthogonally to the audio cable, and then parallel to the audio cable. Is there any difference in the frequency of glitching on the audio line when the antenna is orthogonal versus when it is parallel? If so, you’re seeing crosstalk between the antenna and the audio cable; if not, you’ve got some other problem.

Another very real possibility is that the two PCI cards have an interrupt collision, so each is responding to interrupts targeted at the other. I’d think you’d be seeing a lot of packet loss if this were the case, but it’s possible that the Wi-Fi card has hardware to eliminate spurious interrupts, while the FireWire card does not. This is not as uncommon as you would hope, especially with a cheap motherboard. Check the IRQ settings in your BIOS or your operating system, and see if you’ve got multiple devices assigned the same IRQ. (On Linux, you can check /proc/interrupts.)