No. The call sign is used for the connection between client and server only.
The server would have no reason to include it on a nostr note.
The idea is like winlink. Many servers on multiple bands. Maybe a 40 and 80.
After I get vara hf and reticulum, I want to add in radio control features for the server and a selectable band for the client.
Something where the server will change the frequency, wait say 5 seconds, if no signal, go to the next one, and so forth.
Again, much like a winlink RMS gateway does. The frequencies will be different by server. Perhaps a database or live nostr note with server frequencies and locator identifications