The R-390.  A solid piece of kit for a Cryptologic Technician.  Originally designed by the Collins Radio Company for military and government applications, the receiver was later redesigned as the R-390A/URR in order to reduce the number of tubes and improve selectivity.  Over 55,000 R-390A receivers were manufactured from 1954 to 1984, many of which were installed in Naval surface combatants.


When we first embarked USS HORNE (CG-30) during Operation DESERT STORM, the CTM1 was excited to see us!  Assigned to NSGA Subic Bay, he had been embarked since a port-call in the Philippines and was anxious to get the unmanned space up and running.  During the ship’s transit from the Pacific Ocean to the Persian Gulf, he was hard at work getting the space ready for operations.  That work included calibrating all four R-390’s, one per rack.  Little did he know we had different intentions.  If you could have seen his face when we showed up with three Cubic receivers in hand, and directions to get them installed in the racks and hooked up to RF as soon as possible.  He worked all night getting it done.

At the time, the Cubic receiver was the “latest and greatest” in receiver technology.  The perfect combination of manual and automatic operation, the receiver (actually 2 receivers in 1)  included a knob allowing the operator to “spin and grin.”  Able to both sweep and scan, it rolled through the spectrum with great speed, digits flashing rapidly until energy was detected.  Pausing momentarily, the receiver moved on looking for the next active frequency, unless stopped by the operator for collection.  There was even an emergency clear function, allowing all saved frequencies to be rapidly purged.  (If I recall correctly, the process was to press the Recall button followed by “..911” and then enter.)

The Cubic receiver was a part of our evolution, from analog to digital technology.  Eventually, receivers became remotely operated by a keyboard and monitor.  Whether aboard a submarine, the EP-3E, or a surface combatant, the operator was gradually separated from the receiver.  Whereas the R-390 and the Cubic receiver allowed to operator to sit in front of the equipment and control it directly, banks of receivers operated remotely by a Graphic User Interface (GUI) became the norm.

…and Now

Today, we are witnessing the advent of software-defined radios (SDR).  The polar opposite of the heavy, vacuum tube-equipped R-390, SDRs are rapidly replacing receivers and even transceivers.  An SDR suite consists simply of a computer, equipped with an analog-to-digital converter, connected to an antenna.  The radio functions are replaced entirely with software.  In essence, this means a collection suite could consist of a few computers, connected to RF, and the requisite SDRs.  Instead of installing a bank of receivers, or hand-carrying receivers aboard a ship, SDRs would be used to accomplish the collection mission.

Pictured above is a commercially available SDR.  Plug it into a computer and you are ready to go!


How can Navy Cryptology better leverage software-defined radios?

What other commercial technologies can help us further evolve?

Do we have a culture that allows us to rapidly integrate emerging technologies?