I've played Terrans and a custom race three times now, and I have not ever seen any Starbase Defense Modules. When I look in the Wiki it says they are under 'Starbase Defenses' or 'Starbase Fortifications' and so forth.

There is nothing of that name in the Tech Tree. In fact, I cannot find *anything* that relates to starbases except 'Starbase Militarization' and 'Terrorstars'. the first adds defensive fields for ships, but does nothing for SBs.

What am I missing? The game sucks when you starbases can be killed in one pass by a tiny ship armed with a couple of basic lasers.

EDIT: So I just played another game, this time I took the Yor as my race, and set all the difficulties to the easiest settings, and researched *all* the technologies in the Tech tree before I finally went ahead and crushed the last enemy planet to win the game. Despite having all of the techs that can be researched by the Yor (and 2 techs captured from conquered races), I was unable to build a single SB defense module.

You can no longer rely on the Wiki to be accurate since the Community Update got implemented into the game. Though, to be fair, the Wiki wasn't entirely reliable before, because it never got fully updated to reflect the changes made by the second expansion.

Anyhow, the Starbase Defense modules are still in the game (though greatly reduced in number and overall power).

Battle Stations I - IV are unlocked by the techs Space Weapons, Medium Scale Building, Large Scale Building, and Massive Scale Building. Just like in the vanilla game.

The remaining modules are unlocked by certain Weapons and Defense techs. Specifically: Particle Beams III, Phasors III, Harpoon III, Photon Torpedo III, Singularity Driver III, Graviton Driver III, Shields III, Superior Force Fields, ECM III, PD Combo III, Duranthium III, and Ultimate Adamntium. Did you add the Battle Stations module to your starbases? It's a requirement for all the other Defense modules.
Other than that, I'm not sure what the problem could be.

Hmm some of those Weapon and Defense techs you mention don't sound familiar at all. I will dig up my saved game and check out the tech tree in game to see if they are there. Are those available to all races?

Yes, they are available for everyone.