RE Instruments RE501 Programmable FM Stereo Generator IEEE-488 GPIB 57kHz Pilot

RE Instruments RE501 Programmable FM Stereo Generator IEEE-488 GPIB 57kHz Pilot

The RE Instruments RE501 is a programmable FM stereo composite signal generator designed for testing and aligning FM broadcast stereo receivers, tuners, and stereo decoder circuits. It generates a fully encoded stereo composite baseband signal — including pilot tone, L and R audio channels, and composite output — with all key parameters selectable from the front panel or remotely via its IEEE-488 GPIB interface. Made in Denmark by RE Instruments AS, the RE501 was a professional-grade broadcast test instrument used by broadcast engineers, receiver manufacturers, and service laboratories.

Specifications & What's Included

• Model: RE Instruments RE501 Programmable Stereo Generator
• Manufacturer: RE Instruments AS (Denmark); US support: RE Instruments Corporation, Westlake, OH
• Power: 115V AC or 220V AC, dual-voltage (field-selectable)
• Fuse: 115V = 0.63A Slow Blow; 220V = 0.315A Slow Blow
• Interface: IEEE-488 / GPIB (IEEE STD. 488 Bus Interface, board 901-686)
• IEEE-488 capabilities: SH1, AH1, T6, L4, SR1, RL1, PP1, DC1, DT0, C0, E2
• Modulation Sources: 8 independently selectable per channel (R and L), buttons 1–8 each side
• R/L Level: LED display (0–100%), adjustable via INCREASE/DECREASE buttons
• Pilot Level: LED display with INCREASE/DECREASE control
• Function modes: L&R, L+R, L-R, L only, R only
• Pre-emphasis: Off / 25µs / 50µs / 75µs (front-panel selectable)
• Pilot tone: On/Off switchable
• AUX Composite In: On/Off; Composite Out: On/Off
• Output — COMP: 750 mVp at 100% modulation
• Output — AUX COMP IN: 1Vp at 10%, 1MΩ input impedance
• Output — L OUT: 1Vp
• Output — R OUT: 1Vp
• Output — COMP OUT: 0–2Vp (variable)
• Output — PILOT SYNC: 775 mV
• Output — 57 kHz OUT: TTL level
• Outputs — MOD.S.1 through MOD.S.8: IN 1Vp / 1MΩ; OUT 1Vp (each)
• All signal outputs via rear-panel BNC connectors
• Form factor: Benchtop (desktop enclosure with side handles)
• Calibration sticker on rear: dated 6/23/90 (expired — recalibration recommended)
• Unit only — no cables, manual, or accessories included

Applications

The RE501 is used in FM broadcast and receiver testing environments where a precise, fully programmable stereo composite signal is needed. FM stereo composite generators like the RE501 produce the multiplexed baseband signal — combining left and right audio channels with the 19 kHz pilot tone and 38 kHz suppressed subcarrier — that an FM broadcast transmitter would normally encode. This makes them essential for testing stereo decoders in tuners and receivers: engineers inject a known composite signal and verify that the decoder correctly separates L and R channels at the correct levels with the specified pre-emphasis characteristic. The RE501's eight independently switchable modulation sources per channel allow quick selection of different audio test signals without rewiring, and its IEEE-488 GPIB interface enables fully automated testing — the instrument can be programmed and read back by a controller computer as part of a larger automated test sequence. Pre-emphasis settings (25µs, 50µs, 75µs) correspond to the international FM broadcast standards used in Japan, Europe, and North America respectively, making the RE501 suitable for testing receivers across multiple regional standards. The 57 kHz TTL output is useful for synchronizing external equipment to the stereo subcarrier system. This instrument dates from the late 1980s to early 1990s era of professional FM broadcast test equipment, when IEEE-488 (GPIB) was the dominant remote-control bus for laboratory and broadcast-studio instrumentation.