Hunny Puppy
Occasional Visitor
First up, I want to thank this awesome community and also @RMerlin for the amazing work he's done with Asus Merlin (I've been a follower since the RT-N16U days 
I had a RT-AC86u and it's a TOTAL beast in it's class because it literally beat every other router in it's price (including a Unifi AC LR that I own), it's range of coverage was outstanding and it's speed was brilliant for the range (it's not the faster overall but it is fastest given the range the router can cover). I needed to upgrade to get more speed (and hopefully more range) so I decided to get the RT-AX88U (because the RT-AX86U wasn't available). I've been playing with them both and I wanted to share my feedback after days of testing the stock and the Merlin firmware on these routers.
First up, I want to point out a few fundamental differences I found between the two routers in my testing. Again I'm testing for range and for the best speed I can get from the range (one router to cover a 5000sq ft house).
The RT-AC86U consistently gave me 6-9dB higher signal in both the 2.4 and 5Ghz bands. The 5Ghz band on the RT-AX88U was at a minimum 6db lower than the RT-AC86U at ANY distance (from 5ft to 300ft). I also noticed that the RT-AX88U 5Ghz signal constantly fluctuated by about 4-6dB and was NEVER steady, the RT-AX86U on the other hand was a ROCK steady the the signal levels never fluctuated. For testing purposes, both routers were configured identically and setup up right next to each other using the same bands and settings.
I also found that while the RT-AC86U had a longer range than the RT-AX88U, for the given signal, the RT-AX88U delivered higher speed. So while the signal levels for the AC86U were higher, the throughput at the same distance (with a lower signal level) was higher for the AX88U. I'm chalking this up to the better AX standard (modulation etc). So inshort, it was more difficult to catch the AX88u signal but when caught it performed better.
I noticed a few things which helped boost the signal range and the speed throughput.
1. Put the routers USB ports into USB 2.0 configuration (USB 3.0 interferes with the 2.4Ghz band by creating a lot of radio "noise", this is a known issue with 3.0 ports which has caused me a lot of grief even in laptops).
2. For the 5Ghz band I decided to use the 149 and higher channels. Conventional wisdom tells us that a lower band frequency will travel further, so channel 36 which is around 5.2Ghz should travel further than channel 149 which is around 5.8 Ghz. However one tends to over look the fact that different channels actually have different regulatory power transmission limits. Channel 36 has a limit of about 200mw where as Channel 149 has a power transmission limit of 4000mw, so where as the range is lower, because the power transmission was significantly higher for channel 149 I got a signal much further out and much faster speeds using Channel 149 vs 36 (see this for details https://w.wol.ph/2015/08/28/maximum-wifi-transmission-power-country/). On the flip side, note that devices will also need to use a much higher power to communicate back with the router on channel 149 which may affect battery life. So if battery life is more important than range then stick to a lower channel. Also note that Channel 149 has a maximum width of 80Mhz where as channel 36 can go upto 160Mhz which will make a different in the maximum speed you can get from your 802.11ax devices. I'm not sure if the RT-AX88U supports a split 80+80 channel strategy or if it only supports a contiguous 160Mhz channels. From my reading the 80+80 never works in practice so if you need 160Mhz then stick to channel 36.
Finally coming to the firmware, after extensive testing across multiple different versions of firmwares including the stock and the merlin firmwares, I finally arrived these firmwares which gave me the best range, stable signal levels and the best speed for that range.
RT-AC86U - 3.0.0.4.386_46092 (stock) - https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AC86U/FW_RT_AC86U_300438646092.zip
RT-AX88U - 3.0.0.4.386_46065 (stock) - https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AX88U/FW_RT_AX88U_300438646065.zip
Unfortunately I found that the Merlin firmware were a tad bit slower than the stock firmware (amongst the best versions), although the Merlin firmware had more features in it. If you need to go for a Merlin firmware for the RT-AX88U I found that version 386.8.0 was the best firmware which had a speed and range that was close to the stock 386.46065, the difference was a slightly slower speed and less consistent upload performance. (https://sourceforge.net/projects/asuswrt-merlin/files/RT-AX88U/Release/RT-AX88U_386.8_0.zip/download)
I did however find that any newer version of the firmware were either slower, had a signal fluctuation issues or had lower range. The new 388.xx firmware (both stock and Merlin) performed the worst, had a lowest range and had much slower speeds with less consistent/reliable connections. I don't know what's changed in the 388 vs 386 the difference is day and night.
Thank you all for reading and again this is just my experience. I do wish I had the RT-AX86U based on my experience with the RT-AC86u and from what I've read from benchmark websites and other users but if you had to settle for the RT-AX88U I hope this helps.
If you have any suggestions on how else to juice the range or speed for these routers please feel free to share
These are the Wireless settings I used for testing
And
I had a RT-AC86u and it's a TOTAL beast in it's class because it literally beat every other router in it's price (including a Unifi AC LR that I own), it's range of coverage was outstanding and it's speed was brilliant for the range (it's not the faster overall but it is fastest given the range the router can cover). I needed to upgrade to get more speed (and hopefully more range) so I decided to get the RT-AX88U (because the RT-AX86U wasn't available). I've been playing with them both and I wanted to share my feedback after days of testing the stock and the Merlin firmware on these routers.
First up, I want to point out a few fundamental differences I found between the two routers in my testing. Again I'm testing for range and for the best speed I can get from the range (one router to cover a 5000sq ft house).
The RT-AC86U consistently gave me 6-9dB higher signal in both the 2.4 and 5Ghz bands. The 5Ghz band on the RT-AX88U was at a minimum 6db lower than the RT-AC86U at ANY distance (from 5ft to 300ft). I also noticed that the RT-AX88U 5Ghz signal constantly fluctuated by about 4-6dB and was NEVER steady, the RT-AX86U on the other hand was a ROCK steady the the signal levels never fluctuated. For testing purposes, both routers were configured identically and setup up right next to each other using the same bands and settings.
I also found that while the RT-AC86U had a longer range than the RT-AX88U, for the given signal, the RT-AX88U delivered higher speed. So while the signal levels for the AC86U were higher, the throughput at the same distance (with a lower signal level) was higher for the AX88U. I'm chalking this up to the better AX standard (modulation etc). So inshort, it was more difficult to catch the AX88u signal but when caught it performed better.
I noticed a few things which helped boost the signal range and the speed throughput.
1. Put the routers USB ports into USB 2.0 configuration (USB 3.0 interferes with the 2.4Ghz band by creating a lot of radio "noise", this is a known issue with 3.0 ports which has caused me a lot of grief even in laptops).
2. For the 5Ghz band I decided to use the 149 and higher channels. Conventional wisdom tells us that a lower band frequency will travel further, so channel 36 which is around 5.2Ghz should travel further than channel 149 which is around 5.8 Ghz. However one tends to over look the fact that different channels actually have different regulatory power transmission limits. Channel 36 has a limit of about 200mw where as Channel 149 has a power transmission limit of 4000mw, so where as the range is lower, because the power transmission was significantly higher for channel 149 I got a signal much further out and much faster speeds using Channel 149 vs 36 (see this for details https://w.wol.ph/2015/08/28/maximum-wifi-transmission-power-country/). On the flip side, note that devices will also need to use a much higher power to communicate back with the router on channel 149 which may affect battery life. So if battery life is more important than range then stick to a lower channel. Also note that Channel 149 has a maximum width of 80Mhz where as channel 36 can go upto 160Mhz which will make a different in the maximum speed you can get from your 802.11ax devices. I'm not sure if the RT-AX88U supports a split 80+80 channel strategy or if it only supports a contiguous 160Mhz channels. From my reading the 80+80 never works in practice so if you need 160Mhz then stick to channel 36.
Finally coming to the firmware, after extensive testing across multiple different versions of firmwares including the stock and the merlin firmwares, I finally arrived these firmwares which gave me the best range, stable signal levels and the best speed for that range.
RT-AC86U - 3.0.0.4.386_46092 (stock) - https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AC86U/FW_RT_AC86U_300438646092.zip
RT-AX88U - 3.0.0.4.386_46065 (stock) - https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AX88U/FW_RT_AX88U_300438646065.zip
Unfortunately I found that the Merlin firmware were a tad bit slower than the stock firmware (amongst the best versions), although the Merlin firmware had more features in it. If you need to go for a Merlin firmware for the RT-AX88U I found that version 386.8.0 was the best firmware which had a speed and range that was close to the stock 386.46065, the difference was a slightly slower speed and less consistent upload performance. (https://sourceforge.net/projects/asuswrt-merlin/files/RT-AX88U/Release/RT-AX88U_386.8_0.zip/download)
I did however find that any newer version of the firmware were either slower, had a signal fluctuation issues or had lower range. The new 388.xx firmware (both stock and Merlin) performed the worst, had a lowest range and had much slower speeds with less consistent/reliable connections. I don't know what's changed in the 388 vs 386 the difference is day and night.
Thank you all for reading and again this is just my experience. I do wish I had the RT-AX86U based on my experience with the RT-AC86u and from what I've read from benchmark websites and other users but if you had to settle for the RT-AX88U I hope this helps.
If you have any suggestions on how else to juice the range or speed for these routers please feel free to share
These are the Wireless settings I used for testing
Code:
Wireless - Professional
Band 5 GHz
Enable Radio Yes
Enable wireless scheduler No
Set AP Isolated No
Roaming assistant Disable
Enable IGMP Snooping Disable
Multicast Rate(Mbps) Auto
AMPDU RTS Enable
RTS Threshold 2347
DTIM Interval 1
Beacon Interval 100
Enable TX Bursting Disable
Enable WMM Enable
Enable WMM No-Acknowledgement Disable
Enable WMM APSD Enable
Optimize AMPDU aggregation Enable
Modulation Scheme Up to MCS 11 (NitroQAM/1024-QAM)
Airtime Fairness Disable
Multi-User MIMO Enable
OFDMA/802.11ax MU-MIMO DL/UL OFDMA + MU-MIMO
802.11ax/ac Beamforming Enable
Universal Beamforming Enable
Tx power adjustment PerformanceAnd
Code:
Enable Smart Connect No
Band 5 GHz
Wireless Mode N/AC/AX mixed
WiFi Agile Multiband Disable
Target Wake Time Enable
Channel bandwidth 20/40/80/160 MHz Enable 160 MHz
Control Channel 161
Extension Channel Auto
Protected Management Frames Disable
Group Key Rotation Interval 3600
