ZMA Controller reported the GDT site stopped working and with it; the radar and frequency also went out of service before returning intermittently a good amount of time later. The reporter stated there are no back-ups in place and the equipment is unreliable.

Narrative

I was working Sector 63 and around XA:46 the GDT (Ground Delay Tool) site went out of service; this means that I lost my only frequency and also lost the radar; both at the same time. I was not able to talk or see any aircraft for a good 15 or 20 minutes; not exactly how long it lasted but it was a good amount of time. This situation was very unsafe; our equipment is outdated; unreliable and can go out at any time; we don't even have back up frequencies or radar. I know for a fact that we lost non-radar separation with multiple airplanes; luckily there was no accident; but it could have been worse. After that instance the radar and frequency were intermittent for a good time. The next day; I heard from a peer that the radar went out again and today we are running Sector 63 normal operations pretending that everything is ok and is not. This is a very unsafe operation; and I will continue to say it. This is a systemic issue we have now for years I hope someone will read this and make proper corrections. I am all about safety but I need tools to complete my job at the highest level.I recommend to close the sector completely until a good reliable equipment is in place; we don't even have a back-up system in place. Very dangerous operation. We need a reliable radar and at least two working frequencies.