An upstream signal capture device includes a signal capture circuit having a first port and a second port. The first port of the signal capture circuit is arranged for coupling to a diplexer. The upstream signal capture device also includes an amplifier having a first port and a second port, the first port of the amplifier coupled to the second port of the signal capture circuit, and an analog-to-digital converter (ADC) having a first port and a second port, the first port of the ADC coupled to the second port of the amplifier. The upstream signal capture device further includes a digital threshold detector having an input and output, the input of the digital threshold detector coupled to the second port of the analog-to-digital converter, and a memory configured to capture samples of the upstream signal. When using the upstream signal capture device to capture an upstream signal, a portion of an upstream signal is diverted into an analog-to-digital converter (ADC). A portion of the upstream signal is converted into a digital signal, and when the digital signal exceeds a threshold, the signal is captured in a memory.