R-391 Military Autotune Receiver Collins R-391

  • R-391 video

    ART-13 Military Autotune Transmitter Collins Navy ATC (Army ART-13)

  • ATC/ART-13 video

    Here are my two military "autotuning" radios, a Collins R-391 and a Collins ATC/ART-13. Actually, the term "autotune" is not correct, as it seems to imply the radio is peaking itself for maximum performance on a set frequency. What is really happening is that, in the case of the R-391 receiver, all that is set is the frequency of reception. All other controls are manually set such as filters, audio, BFO etc, and these remain constant regardless of what channel has been selected. The channel selector switch on the R-391 just causes the receiver to change to a preset frequency.

    In the case of the ATC/ART-13, both the frequency and tuning are changed, but first the transmitter must be set to a frequency and tuned up manually for that frequency, then locked into a specific channel switch position. Then, changing the channel switch position will cause all the controls to return to their preset position. In the case of the ATC/ART-13, the two large knobs on the far right (called knobs A and B) determine the frequency. A is effectively the band switch and B sets the final frequency. The three large knobs on the left are knobs E, C and D (in that order from left to right) and are used to actually perform the tuneup similar to any tube operated rig. "C" selects taps on a coil, "D" is a variometer and "E" is the variable capacitor.

    To see a demo of the automatic tuning, select one of the pictures above. Be aware that this requires the Windows Media Player plug-in for your browser, and that the files are large, 4meg for the R-391 and 10meg for the ATC/ART-13. I recently added the original videos to include the sound.

    Here is the sequence of what is happening:

    R-391 -> The receiver is intially set on 7.295mc. You'll see the channel selector switch changed to channel three, where the frequency 3.885 has been preset. First the dials will spin down to the lowest possible range, 00 on the MC display and -965 on the KC portion of the display. There will be a pause of several seconds, while the motors keep turning to get all the cams and pawls aligned at the low end. Then the dials will begin spinning upwards, with the MC dial moving to 3 and the KC dial to 885, and the tuning will stop. Then I will change back to channel 1 and the sequence repeats, returning the radio to 7.295mc. A complete tuning sequence takes about 15 seconds. Since sound is now included I added another clip with a closeup of the MC and KC knobs along with the frequency display window. You can hear a QSO in the background, then I autotune off the frequency, then autotune back to the QSO and it's still coming in fine.

    ATC/ART-13 -> What you'll see here is first I turn on the homebrew power supply sitting above the ATC/ART-13. You'll see a white light come on. Then I'll turn on the ATC/ART-13 and you'll see a green light on the power supply come on as well as a red light (actually looks white in the movie clip) on the ATC/ART-13 itself. This red (white) light indicates the current channel is locked in place. Now I'll change the channel selector, the red(white) light goes out and the dials will start spinning to their base/reset position. Note the far right "B" dial continues spinning for quite a bit longer. While all the other dials can only make one 360 degree revolution, the "B" dial is actually the PTO and makes 20 complete revolutions to go from one end of the band to the other. Once the dials stop, the motor keeps turning for quite a few seconds to get to the base/reset position. Then the dials begin turning in the opposite direction to reach their preset position for that channel. When this is complete, the red(white) light on the ATC/ART-13 will come on indicating channel tuning is complete. NOTE: At one point you will see another light (yellow) on the PS flash on. This is just an indicator that the 30 second delay time (from when the ATC/ART-13 filaments were turned on) has been completed and the HV section of the powersupply has been activiated.

    Hope you enjoy these pictures, Ray W2EC

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