Note
QST, May 1964, p. 7.
The TMC VLRB-1 (Very Low Receiver Band) is a specialized LF/MF (Low Frequency/Medium Frequency) fully solid-state communications receiver manufactured by The Technical Materiel Corporation (TMC) of Mamaroneck, New York. Introduced in 1964. The receiver was designed for continuous-duty commercial and military point-to-point communications.
Built around a main rack-mountable chassis housing individual plug-in modular assemblies (four RF modules, Local Oscillator, 6.5 MHz Oscillator, 6.4 MHz I-F/AGC/Noise Silencer, 100 kHz I-F, BFO/Product Detector/Line Amp, and Power Supply/Audio Amp).
Features an effective IF type noise silencer designed to blank high-amplitude impulse noise before reaching the main detector stages.
AGC System: Fast attack time with front-panel selectable decay times ranging from 3.3 seconds (FAST), 9.9 seconds (MED), to 16.5 seconds (SLOW), alongside manual (MAN) and REMOTE control settings. Maintains output within ±3 dB for a 100 dB change in input signal above 0.3 uV.
Specifications
– Frequency Range: Continuously covers 30 kHz to 600 kHz across five front-panel selectable bands (30–55 kHz, 55–100 kHz, 100–180 kHz, 180–330 kHz, and 330–600 kHz).
– Modes of Operation: AM, AME (AM Equivalent), CW, MCW, FAX, FSK, DSB, ISB, and SSB.
– Architecture: Transistorized double-conversion superheterodyne receiver.
1st I-F: 6.4 MHz (8 kHz bandwidth).
2nd I-F: 100 kHz with selectable 2nd I-F bandwidths of 0.5 kHz, 2 kHz, 4 kHz, and 8 kHz.
Synthesizer Compatibility: Can be operated unsynthesized (free-running local oscillator with 0.01% long-term stability) or linked with an external synthesizer (such as the TMC Model LFSB-1 and CSS-2 frequency standard) to provide 1 Hz or 10 Hz tuning increments. It generates 6.5 MHz reference and 5.8–6.37 MHz spectrum signals for the synthesizer interface.
AFC Capability: Connects with external sideband converters (such as the TMC LFCA-1) for automatic frequency control when tracking reduced-carrier signals.
Audio Outputs: 600-ohm balanced line output 0 dBm monitored via a front-panel meter.
4-ohm speaker output 0.5 watts average) with a dedicated front-panel monitor headphone jack.
Power Supply: Operates on standard AC mains 115/230 VAC, 47–400 Hz, drawing approximately 15 watts, with built-in automatic switchover to an external 24 volt battery power supply (including a trickle charge circuit).
See also closely related VLRC-1.
