Kenwood L-07T (1977–1981)
A pulse counting FM stereo tuner built in Japan with high stability and low distortion.
Overview
The Kenwood L-07T is an FM stereo tuner manufactured from 1977 to 1981. It was made in Japan and features a black finish. This model uses a pulse counting method for FM reception, contributing to its high stability and low distortion performance. While closely related, the L-07T is markedly different from the later L-07T II model, with distinct internal design and service requirements.
Specifications
| Model Rating Type | Pulse counting FM stereo tuner |
| FM Tuner Section Receiving frequency range | 76 MHz to 90 MHz |
| Antenna impedance | 300 Ω balanced, 75 Ω unbalanced |
| Sensitivity | 1.7 μV (IHF), 9.8 dBf (new IHF) |
| SN ratio 50 dB sensitivity Mono | 3.0 μV (IHF), 14.7 dBf (new IHF) |
| SN ratio 50 dB sensitivity Stereo | 35 μV (IHF), 36 dBf (new IHF) |
| Distortion factor (100% modulation) mono | 0.04% (WIDE), 0.04% (NARROW) 100Hz; 0.04% (WIDE), 0.13% (NARROW) 1kHz; 0.06% (WIDE), 0.27% (NARROW) 6kHz; 0.05% (WIDE), 0.05% (NARROW) 15kHz; 0.06% (WIDE), 0.27% (NARROW) 50 Hz to 15 kHz |
| Distortion factor (100% modulation) stereo | 0.05% (WIDE), 0.2% (NARROW) 100Hz; 0.045% (WIDE), 0.15% (NARROW) 1kHz; 0.06% (WIDE), 0.25% (NARROW) 6kHz; 0.35% (WIDE), 0.9% (NARROW) 15kHz; 0.1% (WIDE), 0.4% (NARROW) 50 Hz to 15 kHz |
| SN ratio (100% modulation 1 mV input) mono | 85dB |
| SN ratio (100% modulation 1 mV input) stereo | 80dB |
| Image interference ratio | 120dB |
| Selectivity | 35dB (WIDE), 100 dB (NARROW) at 400 kHz, 60 dB (NARROW) at 300 kHz |
| IF interference ratio | 120dB |
| Spurious interference ratio | 120dB |
| AM suppression ratio | 65dB |
| Capture ratio | 0.8dB (WIDE), 1.4dB (NARROW) |
| Subcarrier suppression ratio | 73dB |
| Stereo separation | 55 dB (WIDE), 50 dB (NARROW) at 1kHz; 45 dB (WIDE), 38 dB (NARROW) at 50 Hz to 10 kHz; 40 dB (WIDE), 32 dB (NARROW) at 15kHz |
| Frequency characteristic | 20 Hz to 16 kHz +0.2 dB -0.5 dB |
| Output and Impedance FM | 1V/1kΩ (1 kHz, 100% modulation) |
| Multipath Output | Vertical: 0.02V/1kΩ (1 kHz, 30% modulation); Horizontal: 0.4V/10kΩ (1 kHz, 100% modulation) |
| Rated power consumption | 28W |
| Power supply | 100 VAC, 50/60Hz |
| External dimensions | Width 480 x Height 100 x Depth 336 mm |
| Weight | 6.9kg |
| Number of Transistors | 46 |
| Detector/MPX scheme | quadrature |
Design
The L-07T uses the pulse counting method, which provides low distortion through linear detection and high stability without requiring adjustment. It features a double conversion design, converting the first IF at 10.7 MHz to a second IF of 1.96 MHz. The RF section employs a DD-MOS type FET (SD 306) known for wide linearity and low noise. The tuner includes a Surface Acoustic Wave (SAF) filter with a linear phase characteristic, using lead titanate (PZT) material resistant to aging and environmental changes, and is shielded in a metal case. The local oscillator uses three-dimensional wiring with a buffer amplifier and shielding. The IF band has two-stage switching (WIDE and NARROW). The MPX section uses a two-stage PLL loop filter and a clean subcarrier system with a built-in pilot canceler. A linear scale signal meter accurately indicates input strength from 0 to 80 dB and performs multipath detection. The audio amplifier uses a high-slew rate operational amplifier, and the power supply includes a large cut core transformer, three large capacitors (3300 μF x2, 2200 μF x1), and a full operational amplifier for constant voltage control to enhance sound quality.
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