SG503

Tektronix SG503
250 MHz leveled sinewave generator Tektronix SG503 Produced from 1974 to 1993 Manuals SG503 Instruction Manual 070-1622-01 Early type SG503 Manual 070-1622-01 s/n: B010100 through B089999 SG503 Manual 070-6770-00 s/n: B090000 and up SG503 Modifications from Wizards Workshop (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

The Tektronix SG503 is a 250 MHz leveled sinewave generator plug-in for the TM500 system.

It was primarily intended to be used as an oscilloscope calibration device for measuring bandwidths up to 250 MHz. Unlike later instruments like the SG504, it does not use a leveling head but was designed and calibrated with high quality coaxial cable (P/N 012-0482-00) to operate as a closely matched system when terminated into a 50 Ω load.

Nine overlapping ranges cover the frequency band from 250 kHz to 250 MHz, with an additional range reserved for a 50 kHz reference frequency.

The SG503 shows the selected frequency on a 3-digit LED counter.

Key Specifications

Frequency	50 kHz, 250 kHz to 250 MHz in nine ranges
Frequency accuracy	Within ±0.7 of one count of the least significant displayed digit for the indicated frequency
Amplitude	5 mV_p-p to 5.5 V_p-p in three decade ranges (terminated into a 50 Ω load)
Harmonics	2^nd harmonic ≥35 dB down from fundamental, 3^rd and higher harmonics ≥40 dB down

Rear interface

The sine output, remote amplitude control input, and a 12-bit non-multiplexed BCD version of the counter value are available via the rear connector.

Internals

The SG503 uses two LC Hartley oscillators, one for 100 MHz and above with an air-core inductor, the other for the lower ranges using switched ferrite-core inductors. Tuning is accomplished via a traditional three-section variable capacitor. After filtering, a regulated power amplifier stage (caution: beryllium oxide in transistor cases!) is followed by a peak-to-peak detector for the amplitude control loop, and switchable output attenuators.

The frequency counter is built from a 10131 ECL prescaler followed by 7490 TTL BCD counters and 7-segment decoders (display not multiplexed).

Notes

The Tek 012-0482-00 cable is made from RG-223 50 Ω double-braid shielded coaxial cable (or equivalent), and is exactly 36" from end-to-end.

Links

SG503 @ amplifier.cd (German) including measurements of cable influence (1 m Belden H-155 as replacement for original cable)
SG503 Peak-to-Peak detector substitute by John K. Bennett AE0AM
SG503 Lab Check In and Calibration by Zenwizard Studios @ YouTube
Tektronix SG503 Refresh and Alignments by Zenwizard Studios @ YouTube