From what you describe it could be related to several things, not least, proximity and impediments, distance and objects, walls, floors etc. And bandwidth draw comes into play as well, then there is firmware, another possibility and could also be partly server related. Wireless hook ups are fine, to a point but not generally as reliable or stable as a hardwire hook up, especially for long downloads or streaming. One thing to do, assuming firmwares)/hardware(s) are compatible, would be to use a wireless access point at the location with the issue. Others will have suggestions that may vary, hopefully Mr. Bob Proffit will chime in since he is likely more familiar with the hardware that you are using, I am not familiar with Sitecom products. It does sound as if you should be able to remedy, at least partly, the problem that you have.
I have recently bought a new wireless card and it is giving me grief. Until now I had been using a laptop to pick up the wireless signal from my router, and pass it along to my PC, and have been receiving excellent speeds (30 Megabit) despite being 2 floors above the router.
I bought myself a Sitecom N300 card to go in the PCI slot of my computer, and my connection is generally extremely slow, and often drops completely for minutes at a time. The strange thing, however, is that it still shows medium to strong signal strength, even when the connection drops completely!
This is completely baffling me! I can't work out what could be causing interference, or why the signal strength doesn't go down when the signal does, or why the internal laptop wi-fi receiver seems so much better than this new card with 2 massive aerials. Unfortunately my ability to move either my PC or router is somewhat limited, but please can someone help shed some light on what is going on?
I'm running Windows 7, fully up-to-date, and the router is a BT Home Hub 3 (I think), with BT Infinity.