Jan 232011
 

High power requirements of Realtek RTL8187L chipset, found in the ALFA AWUS036H USB wireless adapter, can cause ”on and off cycling” and/or dropping of connections and performance issues (see details below).  We have two solutions:

1. POWERED 4-port USB 2.0 hub with an AC adapter

2. USB cable with two A-male connectors: This resolves some power issues for Alfa AWUS036H

3. USB Cable Extender over CAT5/6 cable (up to 60-meters) with power supply (sold separately)

DETAIL:  The Realtek RTL8187L chipset, found in the ALFA AWUS036H USB wireless adapter, is quite power hungry.  That is, it draws much more than 500ma when operating.  USB controllers are rated for 500ma per port and most will shut down the port when the load exceeds ~550ma.  This causes a constant “on and off” cycling of the device in some cases.  The fix is simple… Purchase a POWERED 4-port USB 2.0 hub… one with an AC adapter to provide external power.  The AC adapter is rated to provide 2000ma of power to drive 4 ports @ 500ma each, but will supply a single port with up to 2000ma…. more than enough power to satisfy the Realtek chipset.  This has resolved the problems of performance and signal dropping for our customers.

  3 Responses to “Alfa AWUS036H Cycling on & off and/or dropped connections: Power problem & solutions | Realtek RTL8187L chipset”

  1. Comments from customer – very technically proficient – regarding a related issue: Some Active USB cables (from the same batch) work fine and others do not supply enough power for AWUS036H:
    The voltage is supposed to be 5V from a USB port, but if the variance of voltage is anything like 12V (which could be anything from about 10.5-13), the voltage on different computers could be as low as 4.5. The lower the voltage, the higher the amp draw that is needed. So might be why on come PC’s all is OK, and in other cases, the issue shows up….

    The extension cables we take back, in general, work fine for us on the PCs we try. It is definitely a variance in PCs that causes the issue. We ask customers to try the extension cable with a USB memory stick if they are having issues with it connected to AWUS036H: It always works OK for the USB stick. So, it’s some sort of voltage issue and not sure if it’s the extension cable that is overly sensitive to the voltage or the AWUS036H.

  2. The extension cables we take back, in general, work fine for us on the PCs we try. It is definitely a variance in PCs that causes the issue.

  3. Thank you guys for the above information, it help me a lot,

    my alfa awus036h came with thick usb cable and the adapter was cyclically switching Off & ON,
    I had one more USB cable of thin dia, i just plug that thin diameter cable and it started to work (continuously ON),
    I shall monitor the condition for few more days,

    thank

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