How could a 9KHz-8GHz RF Digital Step Attenuator be used to reduce the gain on a test signal at 1420 Mhz being produced by a NanoVNA, and used to test a hydrogen line radio telescope? Currently the test signal overloads the SAWBird on the radio telescope.

For your application, this type of digital attenuator is actually a very useful addition to your radio astronomy test setup.

If you are using the NanoVNA as a signal source at 1420.40575 MHz, the connections would simply be:

NanoVNA RF OUT
       │
       ▼
Digital Step Attenuator
       │
       ▼
LNA / receiver / SDR input

You would set the NanoVNA to output 1420.40575 MHz, then use the buttons on the attenuator to reduce the signal level.

The PE43711-based attenuator typically provides:

• 0 to 31.75 dB attenuation
• 0.25 dB steps
• Works well at 1.42 GHz (its specified range easily covers this frequency).

For example, if the NanoVNA output is about −10 dBm:

• 0 dB attenuation → −10 dBm
• 10 dB attenuation → −20 dBm
• 20 dB attenuation → −30 dBm
• 30 dB attenuation → −40 dBm

This lets you find the signal level that is strong enough to calibrate your receiver without overloading your SAWBird H1 LNA or SDR.

One limitation is that 31.75 dB may not be enough if you want to simulate very weak astronomical signals. In that case you can simply add a fixed 20 dB or 30 dB SMA attenuator after the digital attenuator, giving a total attenuation of over 50 dB.

For your hydrogen-line work, I think this is a worthwhile purchase because it allows you to adjust the test signal precisely without repeatedly swapping fixed attenuators.