@bprend86 just to be sure it is not interference related, I would disable Wi-Fi on the modem while testing Wi-Fi on the AP. 

Having said that, I have found TPlinks performance to always be less than what is expected. I had basically accepted it for what it is but then tried comparable specification Ubiquiti hardware in its place, under same conditions, and saw superior performance. I would always expect lesser performance on the TPlink side as a general rule. It is budget hardware afterall. Ubiquiti cost more but you get more.

  @RickJamesBish 

Thanks for the feedback, I have disabled the wiFi from the main router and the problem still exists. 

I understand that some detioration is to be expected, however the speed from the TP link never seems to exceed 12-13mbps, regardless of the source internet speed. Could there be some limitation here? I have plugged the ethernet cable from the modum direct into laptop to check speed and it is ok, so not the cable.

  @bprend86  If you have just one wifi ssid with 2.4 and 5 combined, where the router decides which radio a device connects to, separate them and play with channels and channel width for each radio. For example try channel 161 @ 80hz for the 5Ghz channel. 

  @RickJamesBish 

The EAP115 is a N grade (WiFi4) device so can only run on 2.4ghz, therefore 5ghz and band steering wont be your issue.   

This is highly likely to be channel selection and channel width settings.    2.4ghz is a VERY congested frequency and performance is awful in most cases, best thing to do is scan for what channel is the best and choose it, likely the current channel you are on is congested and the Router channel isnt.

Also force 40mhz widths to get faster speeds, in congested setup AUTO will drop it to 20mhz to improve quality at the expense of speed.  

Any details you have would help, pictures of the Airspace, channel utlisition and what settings you have applied for example.

  @RickJamesBish 

Having said that, I have found TPlinks performance to always be less than what is expected. I had basically accepted it for what it is but then tried comparable specification Ubiquiti hardware in its place, under same conditions, and saw superior performance. I would always expect lesser performance on the TPlink side as a general rule. It is budget hardware afterall. Ubiquiti cost more but you get more.

Higher cost does not always result in higher performance, in general under performance reviews the Omada EAPs are extremely close in performance to the Unifi range, in some cases (EAP670 for example) even exceeding the opposition.  Much as you are entitled to your opinion, its demonstrably fallacious and a simple google search will show that, literally the first result. 

https://shorturl.at/uOYZ1

A number of us on here attempted to help you when you setup your Omada system, unfortunately, you didnt follow our advice and when it under-performed you blamed the hardware.   While I have no issue with you doing that, its un-helpful to the user who asked the question when you speak netatively on the product without any real basis for the claim.

Anyways.., disabling the WiFi on the router wont prove anything, its unlikely to be on the same channel or interfering as both are not affected (which they would be if that was the issue).  Its far more likely just the channel the EAP is using is affected, without a scan of channel utilisation this cant however be determined and all we can do is speculate on the cause.  Also channel width may be set at 20 which would drop performance a good bit

Performance for this device should be around 70-90mbps if all is set correctly and the airspace isnt totally flooded, which sadly we cant rule out.

  @Philbert I never said higher costs means higher performance. I said Ubiquiti cost more but you get more, and that has been the case for me without fail. So my experience gives me the basis to make that statement.

I never refused to try anyones advise, the advise given did not fix the issue. 

"Anyways.., disabling the WiFi on the router wont prove anything" That is a complete assumption. Its a simple process of elimination. If he disables it and it does not fix his issue, it proves the WiFi on the router is not causing the issue and he enables it again. Why would you even advise against such a simple process, is it just for the sake of arguing? 

  @RickJamesBish 

I never said you refused the advice, just stated you didnt follow it.. there is a difference..  

"Anyways.., disabling the WiFi on the router wont prove anything" That is completely false. Its a simple process of elimination. If he disables it and it does not fix his issue, it proves the WiFi on the router is not causing the issue. Why would you even advise against such a simple process? Comes across as for the sake of arguing.

Channel interference only happens if the APs are on the same channel, or overlapping channels in which case it would affect BOTH the router and the AP.   The router wasnt causing an issue and didnt experience anything to indicate interference, so we can rule that out and look at channel selection. 

Even if it was the cause and interefence was at play, you then need to go to channel selection to fix it..  its just experience in getting to the resolve as quick as possible. 

@bprend86

Apologies we have went off on a tangent here.  

In short its affecting your 2.4ghz frequency

Its not the Router and AP sharing channels and interferring with each other, so therefore its likely 3rd party WiFi, cordless phones or Zigee/Bluetooth causing it which you can solve by changing channels.  If you are on channel 1 go to 6, if on 6 go to 11.. if on 11 go to 6 or 1..   Also check what channel your router is on to avoid using that channel, try and leave at least 5 channels between the router and AP (1 and 6 or 6 and 11 for example).  

Should you find the majority of channels are poor, which is not unlikely.  Then try 12 and 13 if that is available to you, they are a lot less congested, but not all devices work on those channels so may not be a perfect solution.

OR lastly, the channel width needs to be increased, check this on the AP under settings.  Its usually set for AUTO, switch it to 40mhz to get the fastest speeds but it will interfere more.  Sadly that's going to be unavoidable in most cases! 

  @Philbert and all

Thanks for the responses. Firstly, I have attached some screenshots of the settings below. I have also done some speed tests using different channels, etc. as suggested. Please see below; Please note that the internet is currently unstable that speeds can fluctuate by 0-20mbps between tests. I have just ordered a new service so I need to know if I will need to get a different wifi access point device to get whole house coverage.

                                                                                         Down                    Up

Wired                                                                               52.35                    6.62

Modem 2GHz                                                                 52.74                    7.09

Modem 5GHz                                                                 55.91                    4.75

TP-Link, Auto                                                                  8.06                      7.36

TP- Link, 40MHZ, Ch7                                                   7.48                      6.78

TP- Link, 40MHZ, Ch13                                                 7.37                      6.17

Can you also please elaborate a little on what is meant by congestion? This is a standalone house, closest house is about 300m away. There are a few smart devices but all connected to the modem.

Any advice here?

Internet upgraded yesterday. Getting 250 download from the ethernet cable connecting to the TP-Link and about 5 from the access point..

Thanks in advance

  @bprend86 

Hey

So in short if you are now getting 250mbps or greater into the house you will need to consider upgrading that AP.    The EAP115 is a WiFi4 device, therefore its limited to 2.4ghz spectrum and that has a maximum in real world of around 80mbps.

Have in mind that mbps and MB are not the same, ill try to elaborate and perhaps this is where the confusion is, some test and websites use these interchangeably when they are not.   A 500mbps (MegaBit per second) internet connection will offer around 60MBps (MegaBytes per second) in actual speed, to clarify there is 8Bits to 1 Byte.    In short Internet speeds are measured in mbps, the data itself in MBs.  

Without knowing how you are testing this I can only speculate that this is the answer based on what you are seeing.

So just thinking out loud here, if you are seeing 8MBps, then that's roughly 64/70mbps wireless connection which is what I would expect from the EAP115

So the answer, move to 5ghz.   An AP with 5ghz can give you an 866mbps connection (or faster sometimes) which is around 120MBps and should be therefore faster than you internet connection.    Something like the EAP225 (WiFi5) or the EAP610 (WiFi6) is the obvious choices, WiFi6 would be the faster of the two but the AP will cost roughtly 25% more based on my local pricing.