question on spare key hack

[Sveedy]

" Spare antenna ring " ? This is where I'm getting lost. What is it, and does it get spliced into the wiring ? Or is it some magical piece of plastic that I just shove my key into, and tape it into the column shroud ?
I'm sensing black magic here...

[Krons]

So I have read about this issue before, but am completely ignorant on the particulars. Is there a general write up on what exactly is needed, and how to do it ? My '99 only has one key, and of course I'd like to have a spare.
What is the immobilizer, and where is it located ?
Is it a part I can get from the junkyard ?
Does it get spliced into the wiring ?
Is this a 850 issue as well ?

As I said, I'm completely and totally clueless on this.

No wire splicing.
1. Remove current antenna that surrounds the key tumbler.
2. Place your chipped key in/near the antenna and duct tape it there.
3. Tie band or tape the antenna/key combo (with harness connected) under the steering column.
4. Buy spare keys and have them cut, don’t worry about the chip in them.
5. [optional] Buy spare antenna to make the key area still look stock, but you won’t plug this in.

[abscate]

If you leave the key in forever it might pend a code for this which does not trip a CEL or affect operation. I found this out with my DENSO equipped s70 1999. An me7 1999 like your GLT might not do this

Quoted from Evitas maintenance record

Converted key to new keys with spare antenna ring located under dash - now have three keys to drive!

One funny bit - car does one immob fail cycle of start, stall - then starts flawlessly.
Hmmmmm

Solved mystery ...if key is left in immob to long a ECM 0750? Pops according to web. This maps to P1081, which was present. When I cleared it, car starts immediately
The burning question, how long is too long to trigger code?