How can I defend against tanks in Starcraft 1 TvT?

I'm playing the SC1 campaign and I'm having a really difficult time on one of the missions (where you destroy the ion cannon.)

I can't seem to defend against siege tanks. They come in, demolish my bunkers, and I'm toast.

What defenses can a Terran employ to prevent the base from getting overrun by siege tanks?

Line of sight is your ally on this map. There is a elevated area to the northwest of your base with a few ramps leading up to it, try to place your bunkers/tanks at that ramp rather than in your base, also put up a few turrets to prevent annoying science vessels.

As for the northeast entrance, send out a engineering bay or barracks out that way to scout to extend the LOS for your tanks guarding that entrance. If your tanks get off the first shot, you will beat them. With enough tanks, they won't even be able to finish seige mode before dying.

Here are two tactics I use to fend off a tank attack on this level (other than the two already mentioned):

1) Ghosts with Lockdown Having 2-3 ghosts hit some of the tanks with lockdown (whilst cloaked of course) allows you time to take them out

2) Lots of Stimmed Marines Marines are fairly cheap, and I tend to have a lot of them. Research U-238 Shells (Range) and Stim Packs and remember to focus fire on one tank at a time

The best thing though is using all tactics mentioned here together. Don't throw all your eggs in one basket, as it were.

For example, use the Spider mines as an 'Early warning system', and to soften up the incoming attack. Have the Ghosts Lockdown any Goliaths (and with any energy left, any spare tanks), and using cloaked wraiths to pick off the tanks. Marines to just sweep the floor.

In addition to setting up your tanks in better positions, you can also try,

Siege Tanks + Floating Barracks

Siege tanks have a longer firing range than sight range, which means if you see the enemy tanks before they see yours, you can get off the first volley and that often makes the difference.

Siege up your tanks (preferably on high ground) and then float a barracks far in front to give your tanks more range.

Spider Mines

Spider Mines are essentially free. Place them on the path of the enemy tanks. Plus the computer won't scan when it walks to your base.

Placing mines are a bit tricky. You'll notice that if you select 12 vultures and tell them to all place a mine in a single spot, only 1 mine will be placed by 1 vulture. You need to manually split the vultures and spread the mines.

For an example of killer spider mine placement, check out Boxer's Minetrap from 2005 Season 1 Starleague Finals

Higher resolution video of Boxer placing mines

Cloaked Wraiths

A dozen cloaked wraiths will quickly snipe tanks.

This takes a bit more micro because first you'll have to kill off the marines or goliaths that a computer usually sends along, and then pick off the retreating tanks.

Or you can dodge in and try to pick off the tanks. The computer will scan. Dodge out just as the scan is going down to minimize the damage that is taken. Wait for the vision from the scan to wear off. Dive back in. Repeat.

Drop Goliaths On Top of Tanks

This is how the pros take care of siege lines.

1. Load up two dropships with goliaths and fly them over the enemy siege tanks.
2. When the dropships are over the enemy tanks hit U and then click each dropship to unload them while they're still moving. This is really important because it'll unload units almost a full second faster.
3. Move in your additional ground troops to attack the distracted tanks.