Used RF Signal Generators for Sale

An analog signal generator produces CW (continuous wave), AM, FM, and pulse-modulated signals using a traditional frequency synthesizer architecture. It is the right tool for receiver sensitivity tests, frequency response measurements, and anywhere you need a clean single-tone RF signal. A vector signal generator (VSG) adds an I/Q modulator that can produce QPSK, QAM, OFDM, and digitally modulated waveforms for testing wireless communications receivers. Agilent E4428C is an analog generator; the Agilent E4438C is a vector signal generator that does everything the E4428C does plus wideband digital modulation.

Phase noise is the spectral purity of the signal expressed as dBc/Hz at a given offset from the carrier — for example, -110 dBc/Hz at 10 kHz offset for a 1 GHz output. A signal generator with poor phase noise introduces noise into your receiver or device under test that shows up as increased error vector magnitude (EVM) in digital modulation tests or as measurement floor increases in phase noise analyzers. For most component and system testing, -100 dBc/Hz at 10 kHz is adequate. For low-phase-noise reference sources and VCO testing, you need -120 dBc/Hz or better.

Start from your highest required test frequency and add margin. For cellular base station testing up to LTE Band 42 (3.5 GHz), a 3 GHz generator is the minimum — a 6 GHz unit gives you harmonics clearance. For 5G NR sub-6 GHz, you need at least 6 GHz. For satellite band work (Ku-band at 12-18 GHz, Ka-band at 26.5-40 GHz), you need a 20 GHz or 40 GHz instrument. For radar and EW applications, 40 to 67 GHz generators are used. The HP 83620A covers 10 MHz to 20 GHz and is widely used for microwave component characterization.

YIG stands for Yttrium Iron Garnet — a magnetic crystal whose resonant frequency can be tuned by varying an applied magnetic field. YIG-tuned oscillators (YTOs) are used in most microwave signal generators because they offer low phase noise and wide tuning range in a single stage. The YIG sphere and its electromagnet coil are the most expensive component in a microwave generator — a YIG replacement on an HP 83620A costs $800 to $1,500 in parts alone. YIG failures show up as frequency errors, inability to lock phase-lock loops, or complete output loss above a certain frequency. This is the most common reason a used microwave signal generator needs repair.

Analog signal generators support AM (amplitude modulation), FM (frequency modulation), phase modulation (PM), and pulse modulation. Better instruments add pulse-width control, pulse delay, and internal LF modulation sources. Vector signal generators add I/Q input ports for applying externally generated wideband modulation, and internal baseband generators for producing standard wireless formats (GSM, WCDMA, LTE, 5G NR) without an external signal. The Agilent E4438C with Option 001 internal baseband generator produces most cellular and wireless formats internally.

Annual NIST-traceable calibration is standard for most quality systems. The calibration covers output frequency accuracy at multiple test points, output power level accuracy across the full frequency and level range, and modulation accuracy where applicable. Frequency accuracy on a modern synthesizer drifts very slowly — an instrument calibrated two years ago and stored at room temperature likely still meets spec. Output power calibration drifts more, particularly at the upper and lower level limits, because the attenuator relays and step attenuator contacts change with use. We issue certificates with actual measured data.

YIG oscillator failure is the most expensive repair across all HP and Agilent microwave generators — affects HP 83620/83630 series, Agilent E4428C/E4438C, and all instruments above 3 GHz. ALC (automatic level control) circuit drift causes output power to be out of spec across frequency — often traced to the detector diode or the ALC loop amplifier on the A9 or A11 assembly. Step attenuator relay failures cause level discontinuities at certain attenuation switch points. Synthesizer unlock errors on the HP 83620A are usually in the reference oscillator or the first loop PLL. All of these are bench-reparable.

The HP 83620A is a swept-frequency synthesized signal generator covering 10 MHz to 20 GHz, optimized for fast sweep speed and microwave component characterization. It has excellent phase noise and covers the full microwave range in a single sweep. The Agilent E4428C is a 250 kHz to 6 GHz analog signal generator optimized for receiver test and general RF work — better level accuracy and modulation capability at RF frequencies, but limited to 6 GHz. If your work is microwave component and system testing (amplifiers, filters, antennas) up to 20 GHz, the HP 83620A is the better choice. For cellular receiver testing at sub-6 GHz, the E4428C is preferred.

Signal generator calibration at Aumictech costs $450 for a standard pass/fail NIST-traceable certificate, or $650 for a full certificate with measured frequency accuracy, output level accuracy, and ALC flatness at multiple points. Repair evaluations are free — we bench-test the unit and quote before any work begins. Typical repair costs for a YIG replacement run $1,000 to $2,500 depending on the instrument; ALC and attenuator repairs typically run $500 to $1,200. Turnaround is 1 to 5 business days depending on parts availability.