[Rambo_Gandhi]

Wireless newbie here…

I have a router (R1) with (4) vertical external antennas and an access point (AP2) with 4 vertical external antennas placed at ceiling height on the same wall to extend coverage to a couple of adjacent rooms. Literally all the antennas are lined up 10' apart at the same height on the wall such that it's

l l l l - - - - - - - - - - l l l l

When I purchased the router + AP combo the vendor swore up and down the appliances wouldn't interfere with one another so long as one was operated on channel 36 and the other channel 165.

When appliance (R1 or AP2) transmits traffic with a single client (C1 or C2) it does so at 55MB/s. Sadly when both (R1 or AP2) pass/transmit WLAN traffic for 2 clients at the same time the achieved bandwidth drops to 5-10MB/s. To be clear C1 is connected to R1 and C2 is connected to AP2. The clients are just doing an iperf3 file transfer among themselves.

As soon as I placed R1 on the floor and out of line of site of AP2 (some boxes of stuff attenuating) the achieved transfer is 55MB/s like one would hope.

I don't have any reason to believe the vendor had a batch of units with bad band-pass filters causing spurious emissions outside of the spectral mask. When I check the FCC docs for the appliances, the FCC shows pass for "frequency stability" and "spurious emissions" at a 3M or 9' test distance which is akin to my setup.

https://fccid.io/Q87-WRT1900AC/Test-Report/Test-Report-NII-pdf-2205639.pdf

Because of attenuation to necessary coverage areas I really do need to place these appliances on the same wall, near the ceiling no more than 10-14' apart.

Is there a wireless principle I'm unaware of that explains why R1 and AP2 are diminishing each other so greatly when transmitting at the same time even though the channels are "supposed" to be completely isolated???

Is placing a small strip of RF shielding fabric obstructing the line of site between the router and access point a feasible solution???

I think a strip of RF shielding fabric between them may look tacky but if that is the only solution I'll gladly do it. If that is a feasible solution does anyone here recommend a particular RF shielding fabric to buy???

[spuriousoffspring]

Is your WRT1900AC a Hardware Version 1 or 2? Both?
What version of DD-WRT do you have on each?

I had a very strange & slightly similar issue with the most recent build - 33413 on my WRT1900AC v1.
I was getting a lot of interference from the router to nearby electronics.
Has never happened on any other build.

This probably doesn't have anything to do with your current issue, but worth mentioning.

*If your router(s) is/are a WRT1900AC v1 the most stable & best performing build is 31924.

Something things you could try would be to turn the Transmit Power down on R1 and try a different combo of Wireless Channels.

[Rambo_Gandhi]

The 1900AC is V2. The 1900ACS is V1.

I skipped DDWRT on these units at the advise of DDWRT guru myersw who encourages LEDE instead of brainslayer just because of what's going on with the wireless radio drivers for these units.

This behavior exists with both Linksys FW or LEDE firmware so I don't think it's a FW thing...I wish it were.

I've tested alternating the channels between the units. No dice.

I'd tested the units at lock step transmit power of 0, 4, 7, 10, 13, 16, 19 dBm. Unfortunately the behavior remained unchanged. Only breaking the line of site between the units (metal baking sheet etc) achieves function of 55MB/s. As soon as I pull the metal baking sheet away restoring their line of site, transfers regress to 5-10MB/s.

[spuriousoffspring]

Is there a wall or something else between the two you could hang a small to medium sized mirror, metal art frame, or similar?

You can also cover the back of a wooden frame or even a cardboard poster with copper foil tape.

https://www.amazon.com/Tapes-Master-10ft-Copper-Foil/dp/B00Z8MCJW2/ref=sr_1_4?ie=UTF8&qid=1506976079&sr=8-4&keywords=Copper+tape

That's what I'd do. Something to duplicate the results of the cookie sheet, but looks good.

[Rambo_Gandhi]

Great idea. Maybe a floating shelf like this (with RF dampening material affixed to it) would extend far enough vertically and horizontally to serve as a barrier. I'll have to measure.

http://smile.amazon.com/dp/B001SOUY1C

[Rambo_Gandhi]

Andi over at LEDE forum explains what's going on.
https://forum.lede-project.org/t/5ghz-wifi-spurious-emissions-between-access-points/7091/2?u=crafterlaughter

New units Linksys shipped me behaved the same. I opted to try a pair of Ubiquity Unify UAP-AC-PRO instead.

At the same 10' distance the achieved throughput is only 20% diminished instead of 90% diminished with the Linksys units.

For those interested, I even placed the Unify units immediately beside each other and the achieved throughput was only 54% diminished. My hat is off to Ubiquity!

[spuriousoffspring]

Glad to hear you sorted it out and thanks for updating the Thread!