Poor signal strength and stability can cause a drop in download speed.
Your Internet speed can be affected by a number of factors, but you may not always notice small differences in speed. When you're downloading files, however, slowed speeds are much more apparent. If you're trying to receive a file and it's downloading much more slowly than it should, this could be the result of server issues, connection strength or even your ISP's speed limitations. However, these issues can usually be troubleshooted to some degree and help you figure out fix a slow download.
Server Problems
Sometimes the speed of the download is completely out of your control. If the server on which the file you are downloading is stored is having difficulty or experiencing an influx of traffic, your download will be slow as it attempts to cope with it. Occasionally a slow download can be "fixed" by deleting it and restarting it, but this isn't a guarantee; don't try this unless you're willing to risk just getting the same speed again and having to start all over.
Speed Limits
Your maximum download speed is limited by the "plan" you have purchased from your ISP, which caps all internet speeds at certain levels. For example, you could be capped at about 300 kb/sec, and even if you have the capability to go faster, your ISP won't let you. In cases like this, you can upgrade your plan (if available) to get higher speeds for browsing, uploading and downloading, but this does cost extra; and there is no guarantee that this would fix the issue if other factors are involved.
Connection Issues
Your own connection may occasionally experience problems that cause downloads to slow down quite noticeably. While the exact cause of such trouble may be difficult to locate, a simple power cycle can typically fix most connection issues if the problem is only on your end. To perform a power cycle, shut down all of your computers and internet devices and unplug the router from its power source. Wait 30 seconds; then plug the router back in. After the router has turned on completely, turn on your computers; then attempt to connect as you normally do.
Weak Signal
If you're using a wireless device, you may experience a slow download if you're getting weak and/or intermittent signals from your wireless router. Make sure you're getting an optimal connection strength by moving your computer closer to the router if possible, and move your router away from any obstacles that can block its signal from reaching your computer. If you're getting a stable signal, then the issue is less likely to be on your end.
