SDR Damage Limits

Understanding the Specifications

Maximum RF Input: The manufacturer's specified maximum input power, where available. This is not necessarily the point at which damage occurs, nor is it a recommended operating level. Receivers may overload or distort well below this limit. Some ratings also depend on frequency, duration, or receiver configuration.

Power: The maximum RF input expressed in milliwatts (mW) instead of decibels relative to one milliwatt (dBm). For reference, 0 dBm equals 1 mW, +10 dBm equals 10 mW, and −10 dBm equals 0.1 mW.

Tuning Range: The frequencies the receiver can tune to. Some SDRs have gaps in their coverage or require different operating modes for certain frequency ranges. Reception quality and sensitivity may also vary across the supported range.

Instantaneous Bandwidth: The amount of spectrum an SDR can receive simultaneously without retuning. For example, an SDR with 20 MHz of instantaneous bandwidth can monitor approximately 20 MHz of spectrum at once. Practical usable bandwidth may be lower because of filtering, sampling limitations, or software configuration.

ADC Resolution: The number of bits used to digitize received signals. Higher resolution can provide greater theoretical dynamic range, but actual receiver performance also depends on noise, linearity, filtering, and RF front-end design. ADC resolution alone does not determine receiver sensitivity or quality.

Additional Technical Notes

• SDRplay receivers: ADC resolution varies from 14 to 8 bits depending on the selected sampling rate. The listed 0 dBm input rating is continuous; some models also specify +10 dBm for short-duration bursts.

• SDRplay RSPduo: Supports two independent receivers, with available bandwidth depending on whether one or both tuners are active.

• Airspy HF+ receivers: Use sigma-delta conversion and digital signal processing, making their ADC architecture different from conventional fixed-resolution receivers.

• Nooelec NESDR SMArt V5: Its published 7-bit specification differs from the commonly cited 8-bit resolution of other RTL2832U-based receivers.

• bladeRF receivers: Device-level maximum input ratings have not been verified. A rating for the receiver chip itself should not automatically be treated as the safe limit at the SDR's antenna connector.

• LimeSDR Mini 2.0: The advertised tuning range includes coverage limitations and should not be assumed to provide identical performance at every frequency.

• RX888 MkII: Receiving its full instantaneous bandwidth requires a high-speed USB connection and substantial computer processing capacity.

• Unverified ratings: An unavailable or unverified maximum input rating does not mean the receiver can safely tolerate high RF power.

Protecting Your SDR

Strong RF signals can damage a receiver even when the transmitting radio and SDR are connected to separate antennas. The risk depends on transmitter power, frequency, antenna separation, coupling, and the receiver's input protection.

Static discharge, lightning-related surges, and inappropriate DC voltage applied to the RF connector can also damage receiver components.

When operating an SDR near transmitting equipment, consider using appropriate RF protection:

• RF attenuators reduce incoming signal strength.

• RF limiters help protect against excessive RF power within their specified limits.

• Transmit/receive (T/R) switches or relays isolate receivers while transmitting.

• Band-pass and notch filters attenuate unwanted signals outside the desired receiving frequencies.

Protection devices must be selected for the applicable frequencies, power levels, and required isolation. Simply disconnecting USB power from an SDR does not protect its RF input from a nearby transmitter.

Important: Always consult the manufacturer's documentation for your exact SDR model before exposing its antenna input to strong RF signals. Maximum input specifications are equipment-specific, and exceeding a published limit may cause permanent damage.