@NDIrish 

Thanks for reaching out. I understand that after upgrading your internet and switching to Deco Mesh units, you are seeing much lower download speeds at your satellite location (your office across the yard) compared to the main Deco, despite a significant increase in your provider's speed. Your upload speeds remain stable, but download speeds in your office have dropped, which is understandably frustrating.

Here are some suggestions to help you accurately measure and improve your Deco Mesh network speeds:

How to Accurately Test Your Deco Mesh Speed:
1. Use https://www.speedtest.net or the Speedtest app/CLI (https://www.speedtest.net/apps/) for reliable speed testing.
2. First, connect a PC directly to your ISP modem/router to confirm you are receiving the full speed from your provider.
3. For wired (Ethernet) speed tests, connect your PC directly to the main Deco unit. Ensure all Ethernet cables are CAT5E or higher, and that all devices (modem, Deco, PC) support your subscribed bandwidth (e.g., 1GE ports for 500Mbps, 2.5GE for 2Gbps, etc.).
4. For wireless speed tests, make sure your device is connected to the nearest Deco unit and using the 5GHz or 6GHz band (not 2.4GHz, which is slower and more prone to interference).
5. When testing, ensure no other devices are using high bandwidth (like streaming or downloading large files).

Ways to Improve Speed on Your Deco Mesh:
1. If your wired speed is slower than expected, try different Ethernet cables (CAT5E or above) and alternate Ethernet ports on the main Deco.
2. In the Deco app, go to MORE > ECO Mode and ensure ECO Mode is disabled.
3. Go to MORE > QoS and make sure QoS is disabled. If there is no on/off switch, set it to standard and remove all priority devices.
4. Navigate to MORE > Advanced > NAT Forwarding and disable SIP ALG and UPnP.
5. Try running speed tests on different servers, as some may provide better results.

For more details, please refer to this FAQ: https://www.tp-link.com/support/faq/2429/

If you continue to experience unexpectedly slow speeds, especially at your office location, please contact TP-Link support with the results from the above troubleshooting steps. We can help further investigate whether there is a hardware issue or if additional adjustments are needed.