From TekWiki
Jump to navigation Jump to search
Tektronix SG503
250 MHz leveled sinewave generator
Tektronix SG503

Produced from 1974 to 1993

Manuals – Specifications – Links – Pictures

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

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

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.

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 mVp-p to 5.5 Vp-p in three decade ranges (terminated into a 50 Ω load)
Harmonics 2nd harmonic ≥35 dB down from fundamental, 3rd 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.


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 circuit starts with a ÷8 prescaler (SP1670 and 10131 ECL flip-flops) followed by 7490 TTL BCD counters and 7-segment decoders (display not multiplexed).


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.


Documents Referencing SG503

Document Class Title Authors Year Links
070-2088-00.pdf Book TM500 Series Rear Interface Data Book 1975
070-2088-01.pdf Book TM500 Series Rear Interface Data Book 1976


Year 1979 1980
Catalog Price $1,325 $1,375
In 2023 Dollars $5,600 $5,100

According to an internal memo, annual sales were estimated at 1200 units in 1979.


Early model

Late model


Some Parts Used in the SG503

Part Part Number(s) Class Description Used in
151-0614-00 151-0614-00 Discrete component Tek-made RF power transistor SG503
155-0107-00 155-0107-00 Hybrid integrated circuit leveller SG503