Note
QST, Jan 1968, p. 141.
QST, Mar 1969, p. 109.
Ham Radio, May 1969, p. 51. (SP-400 matching speaker)
The Yaesu FTdx-400, introduced in late 1967, is an historic high-power HF amateur radio transceiver. Released during the transition era between separate transmitter-receiver "twins" and integrated single-desktop units, it stood out as one of the most powerful self-contained table-top transceivers of its time.
Specifications
– Modes: SSB (selectable USB/LSB), CW, AM
– Frequency Coverage: 80–10 meters across 8 segments
80m: 3.5–4.0 MHz
40m: 7.0–7.5 MHz
20m: 14.0–14.5 MHz
15m: 21.0–21.5 MHz
10m: 28.0–28.5 MHz
28.5–29.0 MHz
29.0–29.5 MHz
29.5–30.0 MHz
– Auxiliary: Auxiliary band sockets allow up to 3 additional bands between 3.5 and 30 MHz
– Power Input:
SSB: 560 W PEP maximum
CW: 500 W
AM: 125 W
– Frequency Stability: Within 100 Hz for any 30-minute period after initial warm-up
– Carrier Suppression: Better than 40 dB
– Sideband Suppression: Better than 50 dB at 1000 Hz
– Distortion Products: Better than 25 dB
– Antenna Impedance: 50 to 120 $\Omega$ unbalanced (SO-239 connector)
– Architecture: Double-conversion superheterodyne
– Intermediate Frequencies (IF):
1st IF: Passband tuned from 5,220 kHz to 5,720 kHz
2nd IF: 3,180 kHz
– Sensitivity: 0.5 uV for 20 dB S/N at 14 MHz (SSB)
– Selectivity: 2.3 kHz at –6 dB, 3.7 kHz at –60 dB
– Image Rejection: Better than 50 dB
– Audio Output: 5 W into 8 ohm or 600 ohm loads
Tube Lineup (19 Total)
– V1: 6BZ6 (Receiver RF Amplifier)
– V2: 6BA6 (High Frequency / Local Oscillator)
– V3: 6AH6 (Transmitter 2nd Mixer)
– V4: 6GK6 (Transmitter Driver)
– V5, V6: 6KD6 (2x Final Power Amplifier)
– V7: VR105MT (105V Voltage Regulator / Stabilizer)
– V201: 6CB6 (Transmitter 1st Mixer)
– V202: 6CB6 (Receiver 1st Mixer)
– V203: 6BE6 (Receiver 2nd Mixer)
– V204: 6BA6 (Receiver 2nd IF / Transmitter 1st IF)
– V205: 6BA6 (Receiver 3rd IF Amplifier)
– V206: 12AU7 (Carrier Oscillator / BFO)
– V207: 7360 (Balanced Modulator)
– V208: 12AX7 (Microphone Amplifier)
– V209: 12AT7 (VOX & Relay Amplifier)
– V210: 6BM8 (AF Amplifier / AF Output)
– V212: 6U8 (CW Tone Oscillator)
– V213: 12AU7 (Product / SSB / CW Detector)
Semiconductors
– Transistors
– TR401, TR402: 3SK22G (Dual-gate FETs: VFO Oscillator & Buffer)
– TR403: 2SC372Y (VFO Buffer Amplifier)
– TR301, TR302, TR303, TR304: 2SC735Y (100 kHz Crystal Calibrator, 25 kHz Multivibrator & Marker Buffer Amplifier)
– TR701: MK-10 (FET: Crystal-Controlled Fixed Channel Oscillator)
– TR201: 2SC504 (Power Supply Voltage Regulator Pass Transistor)
– TR202: 2SC372 (Power Supply Voltage Regulator Driver Transistor)
– Key Diodes: 1S145 (Varactor Diode for Clarifier offset tuning), solid-state bridge rectifiers for power supply DC rails.
Power Requirements: AC 117 V or 220 V switchable, 50/60 Hz
