I have a problem with a HDMI/USB extender ST121USBHD

Hi. I am trying to get a HDMI extender to work but I am not getting any video signal.

Source: Lenovo Thinkcentre HDMI running Windows 11 Pro

Connected the local unit to the computer with a StarTech.com HDMI cable

Connected the local unit to the remote unit with the included RJ45 patch cable

Connected the remote unit to my local monitor with a StarTech.com HDMI cable

Windows detects the monitor as “phl bdm4350”. This is not correct as I have a LG monitor.

My monitor acts like its waking up when connecting the extender but no signal is detected.

I have checked the resolution in windows and it is set to 1080p 60hz.

I have no clue to what’s causing the problem and I’m hoping some of you can help me.


Hello Roger and thank you for your interest in our Community.

For dedicated video extenders such as our ST121USBHD, you’ll want to make sure that you are using both Ethernet cables between the LOCAL and REMOTE end. Please also verify that each end correctly connects to the equivalent port on the other end (VIDEO to VIDEO and AUX to AUX) and make sure to use cables of the same length (15m for CAT5e, 30m for unshielded CAT6 and up to 40m for shielded CAT6). The connection must be point-to-point (single Ethernet cable) and cannot go through a network equipment such as a network hub, switch, router or etc.

If this does not work, I would invite you to try different HDMI source and HDMI displays as well as taking note of the LED status lights on the unit, this should give us a better idea of where the issue may be at.

I hope this helps! If you are still unable to get it working, please feel free to reply and I’ll be happy to assist you further.

Emmanuel B.