FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

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macuseri686
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FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

Post by macuseri686 »

So, i recently switched from the ZBT WG1608 router with Quectel RM502Q-AE to a Linksys WRT1900ACSv2 flashed with OpenWrt GoldenOrb and using the https://thewirelesshaven.com/shop/mini- ... dapter-v7/ plugged in via USB, in order to solve a weird issue i was having regarding random modem disconnects and bad WIFI ( viewtopic.php?p=26078#p26078 ).

After setting things up, i noticed that the SINR was SIGNIFICANTLY worse than when i had the modem installed in the WG1608. I was getting about 4-8 SINR previously, but now i was seeing negative 4-10 SINR. At first i thought that i may have connected the antennas loosely, or that the antenna wires were too close to the power supply part of the circuit or something. as it turns out, when i opened it back up to tweak things, the SINR went back to normal. if i put the lid back on, SINR tanks. Also speed tests with the lid on showed 10-15mbps slower speeds for download. My hypothesis is that the metal lid is creating an echo chamber for the signal noise from the USB power supply to bounce around inside and cause interference on the tiny antenna pigtails inside the case.

I have ordered some faraday tape to wrap around the antenna pigtail cables, and i will be 3d printing a new lid out of plastic for the case, to try a few things and see what works. for now, im leaving the lid off
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Didneywhorl
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Re: FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

Post by Didneywhorl »

I've not seen this. I'll have to do some testing now, lol. Thanks
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macuseri686
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Re: FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

Post by macuseri686 »

So, i created a 3D printer .STL file to replicate the lid for the modem enclosure. I added a spot on the top for me to mount a 40mm fan as well to cool the modem. Here is the .STL file if anyone wants to make use of this. Will test the SINR later with and without the faraday tape as well, but ive got a turkey to brine right now.
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Didneywhorl
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Re: FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

Post by Didneywhorl »

THIS!

Love it!
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macuseri686
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Re: FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

Post by macuseri686 »

SINR testing results:

Metal lid on, no faraday tape on ant cables: SINR -4 to -12 dB
Metal lid off, no faraday tape on ant cables: SINR 2 to 4 dB
Plastic lid on, no faraday tape on ant cables: SINR 2 to 4 dB
Plastic lid on, with faraday tape on ant cables: SINR 4 to 8 dB


Also modem temps:

Metal lid with heatsink: 55 C to 60 C
No lid with heatsink: 50 C to 55 C
Plastic lid with heatsink and fan: 38 C to 41 C
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Didneywhorl
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Re: FYI the external M.2 to USB modem adapter needs the lid off due to internal interference

Post by Didneywhorl »

I wondered if the cables would benefit from shielded coverings.

Nice work.
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