If two persons in the Expanse are communicating and don't know where the other person is, how can the communication find it's way to the target?
This goes double if people think the person is on another location than thought, as displayed in S05E07 around 11min 30sec when the Rocinante (Holden) receives the message from Razorback (Kamal). Kamal thought Holden was at Tycho station and would've send the message there. Holden, being close to Alex, receives the message nontheless and without the message passing through Tycho Station (which is mentioned by Holden saying 'Not much of a transmission delay').
With all the ships and the communication passing between them, the only logical explanation would be to use a wide beam and simply burst it out everywhere. That would be a lot of noise in the solar system but it would be an explanation. In aforementioned scene however, Kamal and Draper were hiding from the Free Navy and would've (IMO) avoided sending message that would reveal their position, it would therefore need to be a tight beam.
So, how does a message that needs to go from person A to B find its way if the sender does not know the receivers location?