Shortwave radio cannot ultimately be reliable in the sense of 99.999% uptime. Immediate, unannounced impacts of solar flares actually will knock it out. So long as everything is working correctly, satellite communications are more reliable than shortwave.
What shortwave radio is, is simple. Radio in the 3-30MHz range will bounce around between the ionosphere and the land, potentially for thousands of kilometers. Shortwave does not require locking onto a satellite, nor frequency clocks that run at exactly 70.231 GHz.
You can, if you know what you're doing, build your own shortwave radio in a cave out of a box of scraps.
A shortwave radio in dath ilan is therefore built for exactly one purpose: Exception handling. A shortwave radio is a failover for when something less simple breaks.
And in dath ilan, when code crashes due to an unhandled exception inside an exception handler, the resulting code dump includes a standard message saying the programmer needs to be fired. Shortwave radios are built to work very simply, for when somebody tries to use them during what's at least an exception and possibly some sort of very distracting emergency.
Shortwave radio bands in dath ilan are kept clear, except for regularly spaced audible ticks broadcast all around the planet, whose spacing tells you what frequency you're on and that your shortwave radio is working correctly.
Shortwave radios don't use clever computer-compressed transmission protocols. That would require an inscrutable computer chip, instead of a circuit board all of whose connections you could potentially check by hand using a multimeter. The standard protocol directly transduces voices to amplitude modulations, in a way you could send or receive in the aforementioned cave using your box of scraps.
There is often a computer chip on board a shortwave radio, if it's fancy expensive emergency equipment. But it's not a required chip--you could yank the chip out of the circuit board if you decided you were suspicious of it, and the radio would still work. The chip is designed not to have the physical capability to send outputs that prevent the radio from working. What the chip does do is gently diagnose every part of the system using secondary wires; for regular self-tests, or to light a red indicator light if you've had the incredible bad luck to lose ordinary satellite comms during a solar flare.