Why Does Our WiFi Slow or Stop when my iMac Is On?

[Jodeo]

We have Comcast, 75 gig service (I think — it’s supposed to be sorta fast). We have had numerous periods where it slows to a crawl, stalls, or just plain stops. We’ve tried to troubleshoot this, even buying our own Netgear dual band cable modem (C3700-100NAS).

What tends to correct it is if I shut of my iMac 2007’s WiFi, the other devices and computers work fine. This affects the iMac when it is on, too. (When it’s the ONLY thing using wifi the problem rarely seems to occur.)

Then, when I turn it back on, it’s either fine or reverts back to unusable. It’s hard to predict. There is no rhyme or reason. (It could be my wife's Macbook Air 2013).

This is just normal web surfing and email. No video streams or torrents or bandwidth killers.

Network Utility isn’t showing any clues. Our password is secure (and recently changed). We have two bands (SSIDs), and switching from one to another usually doesn’t help.

My guess is that somehow devices are conflicting. How, I don’t know. That it can be fine for a while and then suddenly happen is weird, too.

Both Macs are running Yosemite (10.10.5) with plenty of RAM and HD space.

Any suggestions on what to check?

 

[Trebuin]

What is your signal strength at the IMac? Regulation mode may fix the problem as well.

 

[Jodeo]

What is your signal strength at the IMac? Regulation mode may fix the problem as well.

All devices have full signal strength in our house. The iMac is about 10' from the router/modem with no obstructions.

How is Regulation mode enabled? I don't see that in my router settings but will keep looking.

As an aside, here's a snap shot from my router log files this morning. Could this have anything to do with this? This is before anyone used the web in earnest today...

 

[Trebuin]

It's odd seeing the DOS in your log, but unless your iMac is attracting that problem, you would have seen the issues across all your devices with your Mac on or off. Check to make sure your firewall is off .

Find 802.11d and 802.11H. One will restrict power or change channels when it detects radar used by air ports and the other will tell the iMac the correct country code. I think 802.11H is what you want to enable. It is a wireless feature.

Are using tunnel or VNC technology's? It looks as if so,done is remoting into your 192.168.0.11 computer.
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All devices have full signal strength in our house. The iMac is about 10' from the router/modem with no obstructions.

How is Regulation mode enabled? I don't see that in my router settings but will keep looking.

As an aside, here's a snap shot from my router log files this morning. Could this have anything to do with this? This is before anyone used the web in earnest today...


View attachment 620530

If your modem is also a router, I would recommend buying a decent router like asus or TD and put the modem in bridge mode. The devices seem to do either on or the other well, I've always had serious issues with combined devices.

 

[Fishrrman]

OP wrote:
"All devices have full signal strength in our house. The iMac is about 10' from the router/modem with no obstructions."

Only 10' away?

Why not turn off wifi on the iMac, and just use an ethernet cable instead?

That's intended to be a serious answer.

 

[Trebuin]

OP wrote:
"All devices have full signal strength in our house. The iMac is about 10' from the router/modem with no obstructions."

Only 10' away?

Why not turn off wifi on the iMac, and just use an ethernet cable instead?

That's intended to be a serious answer.

Mines the same setup, it would be a tripping hazard.