Wireless signal loss with SGB6580 modem. this signal loss happens sporadically. what may be the cause?

Check ALL the cables, and reseat, from your ISP modem and Wireless device. Is the Toshiba near the wireless? Is it Secured with a Password? How many devices are on the wireless signal? There are many thing that cause loss of signal, interference, distance, walls, signal overloading, outside equipment. If you have other devices connected, do they lose signal? If all inside equipment checks out OK, contact your ISP , have them verify the signal or have a ISP tech come out th analize the signal.

Log onto the web interface. Usually http://192.168.0.1 Then go to Wireless Network Setup Then you want to change that to WPA2 for support with ipad.

how can I shut the firewall off so other people in my house can acess the net

Generally the higher the wireless adapter and antenna is placed, the better the signal, however metal can cause some signal loss / interference issues for internally installed antennas. There is usually not a problem if you have an external antenna on your router and it's on top of something made of metal. Only if there is something made of metal between the router and areas in your home that your other wireless devices like a laptop are being used. Also it's a good idea to place the wireless router centrally located in your home if possible. The things that negatively affect your signal the most are obstructions (walls etc), electrical devices that cause interference like cordless phones (especially if they ooperate at the same frequencyb as your router), microwave ovens and other electrical devices that generate interference like motors in fans and such. I think if you place your router and modem on something that will raise them off the metal of your refrigerator it will minimize the effect of the metal from the fridge below them.

You might also consider purchasing a wireless amplifier / booster for your router if you're experiencing signal loss in your home or check your router setup options to see if you can increase the output through the user settings. Use a bi-directional amplifier to increase both your incoming and outgoing signal strength if you decide to go that route.

Have you checked with your ISP on the strength and consistency of the signal before troubleshooting the router. If you're having problems with the wired connection, I would first try connecting directly to the modem to make sure you have a strong signal.
Let me know if you have a strong signal directly from the modem. We can troubleshoot the wireless router once we ensure the signal from the modem is good.
Thanks.

its a wireless signal may have to move it around to get your signal things such as walls ,appliances distance can cause signal loss

Are you using wired ports on the router or wireless?
If you are using wireless, do you have a cordless phone nearby and does the use of it coincide with the loss of internet? Have you tried switching to a wired connection for a short while to see if you are having the same problem? Could be intereference issues with your wireless signal. When you look at the available wireless networks, are there more than one? Could be that your PC/laptop is trying to connect to someone else's wireless if their signal strength is stronger.
If you are using a wired connection on the wireless router and still losing connectivity, try a network connection monitoring tool such as WhatsUpGold (free to try). Have it set up to monitor your PC's gateway address (which should be your wireless router) and some other internet site (Google, Yahoo, etc). If your router connection never drops, but the internet site does, good chance that it's your provider.
Make sure you have the latest drivers for your network device (wired or wireless) and the latest version of firmware for your D-Link. Buggy drivers and firmware can definitely cause flakiness.

You may be far from the modem. Try getting closer. Or it can be of interference. Is there a wireless phone in your area? try removing that.

Check the solder on the vertical output IC this is a common problem and can cause loss of video while sound remains and often will shut the set down with a vertical deflection error

While some loss is expected. You can change channels. 1-6-11 are the best for cutting signal loss because they do not overlap.. 2.4GHz device in operation, like a cordless phone or microwave oven can cause signal loss. Metal in walls, electrical devices and wires can also cause loss.