Coil Whine on 5Ghz. How prevalent?

I picked up an Asus AC86U earlier this year, deciding it was time to upgrade from the N66U and after rejecting the Netgear R7800. Since then It�s been solid as a rock, no complaints.

However, I recently noticed, when all the various PCs and drives were off, a quite distinct high pitch whine from the back of the unit.

My suspicion and a little bit of investigation found it to be coil whine being emitted by the 5Ghz radio. I fiddled with some settings but didn�t find anything that reduced it.

I can put up with it as it�s �masked� most of the time and any RMA replacement would be a lucky dip. 5Ghz isn�t essential where I live as the 2.4Ghz band isn�t likely to get congested and I have to extend coverage anyway with a TP-Link mini router which is hard wired (doesn�t make a peep on 5Ghz)

That said, I�m curious how prevalent electrical noise issues are with 5Ghz and whether it would in any way affect performance? I�ve found a handful of �whine� reports related to routers. My experience has often heard it from power adaptors and the like, as well as Intel Core CPUs but not a router before.

I used to have a few BT HH5 routers and just one of them exhibited coil whine on 5GHz wireless so it does happen sometimes. I now have a few AC68U and AC67U routers and don't experience any coil whine so I think it's quite rare. Probably worth raising an RMA.

My 86U has no audible whine on its 5GHz radio. I know the noise you mean and it is often heard in cheap transformers, I agree.

If you bought it from a good retailer and fairly recently, you should be covered under warranty. If the noise stops and starts when you disable/enable the 5GHz radio, it is a reproducable fault. You would have to explain the issue to the retailer and you are liable for return postage but they are obliged to ship the replacement.

Thanks guys.

I had a look on SNB and found complaints about Netgear/Asus kit, including the N66U. I must dig my old one out and try it. I noticed nothing using it but then had little in the way of 5Ghz capable kit back when I bought it, so rarely had it enabled.

This Overclockers thread has someone specifically mentioning the AC86U. They tried two replacements without joy. I bought mine in April this year with a 2017 manufacturing date, so may have similarly copped unlucky.

I purchased from Amazon, which should be a painless RMA. Not something I�ll put in until the festivities are done with.

FYI - Bar stating it was most likely a fault, Asus tech support didn�t seem that interested. Directing me to the retailer for the entire warranty period. Might be a concern should there be other issues in years 2 & 3 as I thought retailers only covered the first year.

No issues with BT Smarthub... It sounds faulty to me the one you have.

I have just done an RMA for an 11-month old 86U through Amazon which had lost wifi and the RMA was painless.

I went to My Orders, found the purchase, selected "I have a problem" and got through to Technical chat. In the initial "What do you need help with?" box I explained that wifi was not working. The chat operator was polite and asked for more details so I simply stated that I had tried powering off, tried re-flashing and tried firmware recovery. After waiting for a few minutes, they admitted that it sounded like a hardware fault and they would send an identical replacement and a Freepost return label.

All in all, very painless. Just state the facts and what you have tried. If you tell them the high pitched whine comes and goes as you start and stop the 5GHz wifi and you believe there is a hardware fault, you should be fine.

As the AC86U has a fairly powerful CPU - certainly far more powerful than ISP supplied tat - it may be normal for the router to emit a whining noise. I say this as someone who has used the Asus ROG GT-AC5300 and Netgear X10, both of which are extremely powerful and emitted a whining noise when in use, however actual performance was unaffected. Having said all this, I would still RMA the router (if still in warranty) just to rule out a duff unit.