Express vs Extreme

[divergirl]

So i have a rather curious conundrum. I've had a 2014 retina iMac for a little over a year now. For reasons unbeknownst to me, from day one the ethernet has been horrible on this machine. It cuts out every couple of minutes even though pings still go through, and Apple Support can't make heads or tails of the problem. I know it's not the cord, because I've tried swapping out cords. I know it's not the router, because I've tried plugging the exact same cord into my laptop and it works flawlessly. The problem is definitely the iMac.

However, because the machine runs well otherwise and wifi works flawlessly, I have decided to just leave things as is for now. I do have AppleCare with the three-year warranty, so I suppose I can always get it taken in in the future if I change my mind.

HOWEVER, I have recently run into a NEW conundrum. I have an incredibly narrow computer desk due to my workspace (okay, actually it's a card table ssshhh), which makes using dual monitors impossible. But I occasionally do need an extra monitor when I'm doing video work. So I purchased this portable USB 3.0 monitor, so that I can plug it in when I need it and tuck it away the rest of the time.

The issue? It kills my wifi. Like to a crawl. And it's definitely the monitor. The wifi will be perfect, then I'll plug in the monitor and the wifi immediately cuts out and will not return until I unplug the monitor. Which is... vexing. Googling the issue brought me to this page by Apple which states "Certain external monitors and LCD displays: Certain displays can emit harmonic interference, especially in the 2.4GHz band between channels 11 and 14. This interference might be stronger if you're using a notebook computer with the lid closed and have an external monitor connected. Try changing your access point to use 5 GHz or a lower 2.4 GHz channel."

Greeeeattttt. Well, unfortunately while my router broadcasts 5 GHz, it does not support broadcasting the 5 GHz network on a separate SSID, and due to distance from the router my iMac will only connect to the 2.4 GHz network. I tried every single channel on the 2.4 GHz network and it didn't help one iota.

So my question is, did anyone else have this issue, and did switching to a 5 GHz network actually fix it? Because I have an ethernet cord just lying under my desk that runs directly up to the router, so I'm considering buying an Airport Express and plugging it into that cord to broadcast my own little 5 GHz network in the basement, but I'm not sure it would actually help or not. I just want to be able to use my external monitor and the wifi at the same time @-@

Also, does the Airport Extreme use a different 5 GHz signal than the Express? I'm wondering if I'd have more luck with one versus the other. I have no need to connect wirelessly to other devices in my house and we're only on a mid-tier DSL, so I didn't think the Extreme would actually give me any advantage speed-wise, but I'm wondering if it would have any advantage interference-wise. Because that's my real issue here.

 

[JohnDS]

It sounds like you have a pretty long ethernet cable. More than 50' maybe? Is this a name brand cable with moulded ends, or did you buy it from a computer shop where some guy in the back room cut off a length of cable and then crimped some ends on it?

If the latter, your problem may be caused by improper pinouts. An ethernet cable depends on interference between the twisted pairs of wires in the cable to cancel out collisions. If whoever put the ends on the cable did not know the proper pinouts, he may have connected it is such a way that it will work with slower ethernet connections but not with faster ones like your Mac.

Someone who does not know what they are doing would likely connect the twisted pairs to the pins like this: (1,2),(3,4),(5,6),(7,8) whereas they have to be connected like this: (1,2),(3,6),(4,5),(7,8).

The quick and dirty way to check this is to look as the wires going to the centre two pins. One should be blue and the other blue with a white stripe. If the two centre pins have wires of different colours, then your cable is misfired.

You can read the full explanation and see the proper pinouts here: http://pinouts.ru/NetworkCables/ethernet_10_100_1000_pinout.shtml

Also, for gigabit ethernet, the cable should be labelled as either CAT5E or CAT6. This should be written on the side of the cable.
[doublepost=1467054774][/doublepost]In direct response to your question, the Airport Express should work fine, provided that the ethernet cable is correctly wired and is of the right type.