Okay, I know that pondering about the physics (or any science, or the canon, or the aliens, or the religions, or ... well, anything) of Stargate usually leads to migraines and having to go lie down for a few hours, but I just have to ask and deal with the consequences.
1. Atlantis has an iris over the stargate.
2. Therefore should not the Atlanteans have their own GDO/IDC-broadcasting things?
And yet we haven't seen them. At least, I don't think we've seen them -- what we've seen is gate folks interpreting IDC codes using a Dell laptop. (The prevalence of the Inspiron in the Pegasus galaxy still makes me giggle. I mean, I know they brought them along, and I'm sure Dell gives a great military-bulk discount, but I associate the blue-topped Inspiron very strongly with poor students, so.)
3. I want to see Atlantean IDC-ish things. Because they would be cooler. I mean, at some point Stargate Command said "hey, it would be really handy if an IDC code could come with an attached preselected message," so now SG-1 can just send a little message that says "hi, it's us, we're under fire." Or whatever. But the Atlanteans should have something better than that, because they can turn on their technology just by thinking at it. So they could just have little GDOs under their skin, where they couldn't be taken away, and where no amount of torture would reveal the codes because it would all be brain-wave based, and then Sheppard could think "Atlantis, it's us, we're coming home, four coming through" and the iris would automatically close right behind them. Or, you know, the Genii want to walk through with Sheppard, and he'd just think "keep the door locked for the first few guys, but make sure it's open for me." And it would, because all he'd have to do is think "I'm stepping through now" just as he hit the event horizon. And sure, maybe a Genii would get through if they were in lockstep, but whatever. It would still be cool.
We all know Atlantis is like a big puppy around Sheppard; it's mean of them to not let it run to the door when he comes home. Metaphorically speaking.
Actually, on the GDO subject, I've always wondered about the iris. I mean, the idea is that it keeps stuff from rematerializing (which should really mean that the stuff doesn't go thump, because it isn't there to go thump), but we know that the Ancients built the gates, and that they can write code for the gates which prevents certain things from going through an event horizon. It's unclear whether atmosphere goes through, but we know that water doesn't -- Sam says something stupid about density, I think, in the episode Watergate. So couldn't the Ancients have written code that doesn't allow Wraith DNA through? That would be cool; they could send their darts through all the wanted, but the pilots wouldn't come out on the other side. I mean, an iris is a useful backup and protects against the things they haven't specifically excluded yet, but surely we can do better just by messing with the gate. Wraith walks in, gets put together all wrong on the other side. It would be fun!
(The stargate baffles me. It needs to be connected to a power source to receive wormholes, except when we go to Hadante. It won't close if there's a radio signal being sent through, except when it closes right behind Our Heroes. It won't close on matter, except when it does. It doesn't open if there's material inside the ring itself, unless the material is not that dense (water, sure, but I predict that burying it in sand would not be that effective), but clear that out and it'll whoosh open and destroy everything in its path.)
Clearly, I need to stop thinking about this. Because trying to logic it out will only break my brain.