Radio Bench
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Connect RTL-TCP and SpyServer

Radio Bench can receive samples from RTL-TCP and SpyServer. The server must be reachable from the computer that runs Radio Bench.

For a receiver with a KiwiSDR listening URL, see Use KiwiSDR.

Connect RTL-TCP

  1. Select RTL-TCP in the Source panel.
  2. Enter the server host and port.
  3. Select tuner AGC, RTL AGC, PPM correction, IQ DC removal, and gain options.
  4. Select Connect.

The default RTL-TCP endpoint is localhost:1234. Stop streaming before you change the host or port.

The server reports its tuner type and gain steps. Radio Bench shows the same sample rates as the local RTL-SDR source.

Connect SpyServer

  1. Select SpyServer in the Source panel.
  2. Enter the server host and port.
  3. Select Probe to read server capabilities.
  4. Select the sample depth and an available gain.
  5. Select Connect.

The default SpyServer endpoint is localhost:5555. A probe must report gain capability before Radio Bench enables the gain control.

The server decides the tuning range, the sample rates, and the sample depth that it allows. Radio Bench shows only the values that the probe reports.

Improve reliability

Open Settings > Network > RECEIVE BUFFER > Buffer. More buffering tolerates uneven sample delivery but increases receive delay.

Preset When to try it
Low latency (50 ms) A stable connection where tuning response matters.
Balanced (200 ms) Start here, then compare reliability and delay.
Resilient (500 ms) Repeated dropouts on an uneven connection.

Disconnect and reconnect the source after changing the preset. A saved value does not change the current connection immediately.

Read the live buffer status

Settings > Network > LIVE STATUS describes the active network stream.

Reading Meaning
Effective buffer The active buffering target, or the timing cap shown during FSK reception.
Filled now The samples currently buffered, expressed as milliseconds of audio time.
2 s average The average buffered time over the last two seconds, with its minimum and maximum.
Underruns The receiver ran short of buffered samples. Repeated increases can explain gaps.
Overruns The buffer filled beyond its capacity. Samples could not all be retained.

A source can require a minimum buffer for delivery bursts. That minimum can exceed your selected value. Compare the live status after reconnecting.

FT8/FT4 reception applies a timing-related buffer cap. A larger preset cannot correct a wrong clock or missed slots. See FSK timing checks.

Prefer a wired connection when possible. If counters keep increasing, check network stability and computer load before adding more delay.