The HP 3708A Noise and Interference Test Set injects a known‑spectral‑density noise signal into the IF section of a microwave radio receiver, allowing precise carrier‑to‑noise (C/N) ratio control. An automatic levelling algorithm also maintains a demanded carrier‑to‑interference (C/T) ratio, simplifying performance evaluation in the presence of jamming signals.
The instrument includes a true‑RMS power meter, programmable HP‑IB interface, BNC connectors with 75 Ω impedance, and optional rack‑mount kits. It operates from 100‑240 V AC, consumes up to 150 VA, and meets environmental limits of –40 °C to +55 °C. Detailed specifications cover noise level range, flatness, group delay, and power‑measurement accuracy.
| Noise level range | +6 to -80 dBm (approx.) |
|---|---|
| Noise density range | -70 dBm/Hz to -154 dB/Hz (approx.) |
| Noise power accuracy | ±0.25 dB ( +6 to -10 dBm ) |
| Flatness (70 + 20 MHz) | +0.2 dB |
| Group delay (70 + 20 MHz) | 6.2 ns |
| Input voltage | 100/120/220/240 V AC |
| Power consumption | 150 VA max |
It injects noise of known spectral density into the IF section of a microwave radio link receiver to establish a demanded carrier‑to‑noise ratio.
The HP 3708A can be powered from 100 V, 120 V, 220 V, or 240 V AC.