Voxl2 Wifi is dropped periodically in 802.11 b/g mode

[ysoh]

Hi!

I'm using Voxl2 Flight Deck with USB-Wifi Adapter (AWUS036ACS) in my project.
but wifi range is too short for my project due to 5GHz mode. so i tried to change
wireless mode to 802.11 b/g mode (2.4GHz bandwidth). but wifi connection is dropped a few seconds periodically.
i checked 802.11n mode is working without connection drop.

how can i fix it?

here is my sdk configurations.

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system-image: 1.6.2-M0054-14.1a-perf
kernel:       #1 SMP PREEMPT Fri May 19 22:19:33 UTC 2023 4.19.125
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hw version:   M0054
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voxl-suite:   1.0.0
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current IP: wlan0: 192.168.10.90
--------------------------------------------------------------------------------

then wireless link info (802.11b mode)

voxl2:/$ iw dev wlan0 link
Connected to 10:0c:6b:e5:d5:f3 (on wlan0)
        SSID:
        freq: 2412
        signal: -20 dBm
        tx bitrate: 11.0 MBit/s

        bss flags:      short-slot-time
        dtim period:    0
        beacon int:     100

thanks.