That would seem to be the only solution - but you lose all the presumed advantages of meson/neutrino comms, such as un-interceptability, un-jammability, etc. And you gain all the disadvantges of EM comms.
There might be a network of known relays. Put up a GPS satellite / Meson Communications net, and a Portable Meson Comm can use them to
1} Get its' own exact location, local time, and any steady vector it is moving along, and
2} The exact location of several relay satellites.
This is all photons / EM band stuff, pretty standard -- but the PMC is not transmitting.
A military-starship Meson Communicator might not use an artificial GPS signal to determine is' own position, it might use star-tracking on a set of pulsars / quasars to determine exact position, time, and movement. A military Meson Relay might do the same, and broadcast its' exact position only as a highly encrypted signal.
The PMC then (using Meson Comms) informs the relay of its' location, and performs an authentication handshake. It can then request:
A} Any cached messages;
B} To cache a message for a specific recipient;
C} To have its' location passed to a specific recipient;
D} To obtain the current known location of a specific recipient;
E} To form a real-time link to the relay; or
F} To form a real-time link to a specific recipient.
I can imagine paranoid PMC operators setting up a remote (perhaps even disposable) antenna, with a secure (wired!) connection to the communications set. The location of the antenna must be known, but the operator can be some distance / outside of minimum-safe-distance in case someone it waiting for co-ordinates.
Also worth noting: A Meson Communicator would necessarily be tied to a vehicles controls & drives -- so that it can determine how to compensate for any movement, and so that it can communicate its' expected movement to the other end of the link.
, while the individual handsets/suit comms/commdots use EM radiation to talk to the meson tower.
