Jerry,
If you have the nodes and frequencies, and if one of those nodes is near enough for you to hear now, then you probably only need to find out if a PL tone is used. (There usually is a PL tone used with an IRLP node.) Plug in that PL tone in the appropriate place and that's about it. There are a few 'hints' you should be aware of. One of them is that it takes a little time for all the nodes to link, which means that a sort of short pause after pushing the 'talk' button and your first word is required. How short is that short pause? It can be variable. If you start by saying "This is..." before your call sign, that's usually all that's required, so how long is, "This is..."? Otherwise, it's very common for the first word or two to be 'cut off'. It's also very common for 'doubling' to occur, so listening before talking is nice, don't get in a hurry.
If there are no local nodes that you can 'hit', then you're out of luck. Unless you want to buy and operate your own. (ouch!)
Have fun.
- 'Doc
