Thanks for your remarks I added my comments below in red.
I have tried all the options you mentioned including the MAC filtering on the router only and NOT on the repeater and the lower power setting of the router.
Conclusion is that the existing option performs best.
The question is still how to add more MAC addresses to the repeater (32 should be possible)
Wireless Configurations
Links>Wireless Installation Considerations and Managing Signal Congestion
• What wireless modes are you using? I use repeater mode
• 2.4Ghz Routers only: Try single mode G or N or mixed G and N?
• Channel Width set for Auto 20/40Mhz or try 20Mhz only. Is set for 20 only
• Try setting a manual Channel to a open or unused channel. 1, 6 or 11. 11 for single mode N if the channel is clear.
• What security mode are you using? Preferred security is WPA-Personal. WPA2/AES Only. Some WiFi adapters don't support AES, so you might want to try TPIK only or Auto TPIK and AES. I use WPA-Personal. WPA2/AES
• What wireless devices do you have connected? Ipad, iphone, W7 PC, W8 PC, Vista PC, Android phones,..
• Any cordless house phones? 3
• Any other WiFi routers in the area? Link> Use InSSIDer to find out. How many? 13
• If you have any of these options, Try turning OFF or ON Short GI, WLAN Partition, HT 20/40 Co-exhistance and Extra Wireless Protection if you have it. Recommended settings are default. Under Advanced/Advanced Wireless. Short GI is unchecked,
• Enable WMM Enable Under Advanced/Advanced Wireless. Is enabled
• Try setting Medium or Low power output settings and test again Under Advanced/Advanced Wireless. High has the best performance.
Roekroek