ART-13 Restoration Project
The ART-13 is a radio transmitter capable of delivering more than 100 W of RF power and operating in the range 2.0-18.1 MHz and. So, it covers the 80-, 40-, 30-, 20- and 17-meter amateur
radio bands though, in practice, I have been unable to get a reasonable output power at the extreme upper edge of the band (i.e. around 18.1 MHz), because of the low RF power tube grid current that is
obtained (even re-adjusting the frequency multipliers tuning). The transmit frequency is determined by an accurate and stable variable frequency oscillator that is called HFO (High Frequency
Oscillator). If equipped with the LFO (Low Frequency Oscillator) option, the ART-13 can also work in the 200-1,500 kHz range, but that band is of little interest for amateur radio purposes. This was a Swap Meet fugitive. This unit had been left exposed and needed a lot of work. I spent many hours cleaning and doing all of the metal work to make this a nice transmitter. I repainted the panels and replaced the meters as the originals were faded. The electronics needed most of the caps changed and a few resistors.
The Front Before restoration. Chassis Stripped for Work.
The switches before and after cleaning. After cleaning the switches.
View of the top of the chassis, during the cleaning, and servicing process. Top View after cleaning.
View of the Underside and also the output side.
Final Position with BC-348, ARR-15 coming soon.
Power Requirements and Accessories
The T-47/ART-13 power requirements were supplied by a dynamotor that ran on the aircraft +28vdc battery/charger system. The aircraft battery buss supplied the +28vdc@10Amps necessary for the transmitter's tube filaments and relay operation while the dynamotor provided a dual output of +400vdc and +750vdc. The dynamotor would have the two B+ levels connected in series for the HV Plate ( +1150vdc) below 20,000 to 25,000 feet altitude but a barometric pressure switch (located inside the dynamotor housing) would separate the outputs at higher altitudes and only allow +750vdc maximum to prevent arc-over. There were four types of dynamotors used, the DY-17, the DY-11 and the DY-12 (after WWII an improved DY-17A was produced.) The shipboard TCZ featured two types of power supplies, a 115vac operated power supply (of enormous proportions) that supplied the required +28vdc, +400vdc and +1150vdc directly to the transmitter Additionally, the 115vac unit had a motor-generator that provided +14vdc and +28vdc (the +14vdc was required for relay operation inside the ac or dc operated TCZ power supply.) The115vdc operated TCZ power supply used two dynamotors that ran on 115vdc input and provided +14vdc and +28vdc output on one dynamotor and +400vdc and +1150vdc on the second dynamotor. The USMC had a vehicular set-up that installed an ART-13 transmitter with a BC-348 receiver that operated from the back of a Jeep and ran on the +28vdc battery system with HV provided by a DY-12 dynamotor. The antenna used was a whip.
Autotune and Vacuum Tube Information
The T-47/ART-13 featured an advanced Autotune system that would automatically tune up to 11 preset channels (10 channels plus one LF channel) selectable by a front panel switch. The Autotune system would tune the transmitter frequency and output network to mechanical presets that then would match a properly selected antenna. The Autotune cycle took about 25 seconds to complete. Switch position MANUAL would allow manual adjustment of the tuning without disturbing the Autotune presets. MANUAL had to be selected with the transmitter powered up so the Autotune would properly "mechanically" select the MANUAL position (in other words, with power off you couldn't just place the switch in MANUAL and be in MANUAL.) The T-47/ART-13 uses an 837 as the variable frequency oscillator, two 1625 tubes are used as multipliers, an 813 as the power amplifier and two 811 tubes as the P-P modulators. There are also two small modules. One provides the audio amplifier and sidetone amplifier using two 6V6 tubes and a 12SJ7 tube and the other module, the MCW/Frequency Calibration Indicator, uses two 12SL7 tubes and a 12SA7 tube. FCI allows the operator to calibrate the frequency of the transmitter by providing a 50kc calibration signal derived from a 200kc crystal oscillator. The earlier ATC transmitter used a slightly different FCI module that used two tubes and had a rather large plug-in crystal
Frequency Coverage and More Accessories
The transmitter frequency range is from 2.0mc to 18.0mc, however many Navy T-47/ART-13 transmitters were equipped with a plug-in Low Frequency Oscillator (LFO) module that allows the transmitter to operate from 200kc to 600kc or 200kc to 1500kc (at somewhat reduced power, CW only.) Early LFOs have a frequency range of 200kc to 1500kc in six ranges while the later LFOs cover 200kc to 600kc in three ranges. The LFO module uses a single 1625 tube. There are some indications that the Navy preferred the 200kc to 1500kc LFO while the USAAF used the 200kc to 600kc LFO. Many versions of the T-47/ART-13 will have a blank plate installed where the LFO module was installed (along with a plug-in resistive load substitute for the LFO's 1625 filament.) After WWII, the USAAF/USAF didn't use the LFO module but the USN still did. This statement is according to the USAF Extension Course 3012 book on "Radio Mechanics" although this book is from the 1950s and may reflect the uses of the LFO at that time rather than during WWII. Many transmitter installations also used a separate antenna tuner and three selectable condensers to allow easier loading into various antenna impedances at lower frequencies. Also most installations on aircraft included a small Remote Control Panel that allowed the pilot to operate the transmitter from the cockpit. There are a couple of different remotes and a few different antenna tuners that could be used depending on the installation requirements. There were at least a couple of different shock mounts available depending on the version of ART-13 and where it was located. Shock mounts provided vibration isolation and elevated the transmitter to allow convection cooling.
T-412/ART-13B or AN/ART-13B
There was also a T-412/ART-13B that added a 4 channel LF/MF and 20 channel HF crystal oscillator module, the CDA-T in place of the LF module. With the selection of each of the channels 1 to 10, two different crystals could be selected giving two frequencies per channel or a total of 20 HF channels in all. With the CDA-T, the lower end of the frequency coverage was extended to 1670kc. The LF position allowed the selection of four crystal controlled frequencies on the CDA-T module. The remote used with the "B" version will have a toggle switch to allow selecting either crystal frequency per channel selected. All "B" versions of the ART-13 are conversions of earlier ART-13 and ATC transmitters. The installation of the crystal oscillator module required extensive modification of the transmitter circuitry with several additional components. The transmitters were also referred to as AN/ART-13B when using the JAN system.