A filter attenuates frequencies above its cut-off frequency of 40 MHz. What type of filter is it?

A filter that attenuates (reduces) frequencies above a certain cut-off point is deliberately allowing the frequencies below that point to pass through easily. This describes the fundamental operation of a low-pass filter. In amateur radio, low-pass filters are commonly installed on the output of HF transmitters to prevent unwanted higher-frequency harmonics from reaching the antenna and causing interference to VHF services, such as television or FM broadcasts. High-pass filters do the exact opposite by blocking lower frequencies and passing higher ones. Band-pass and notch filters affect specific ranges rather than providing a simple cut-off threshold for everything above a certain point.