hp346 noise source

Let's say I want to have a variety of ENR values, but I only have one HP346 noise source, with an ENR of 15.2dB a tsome frequency.

Would adding a 3dB attenuator to the output of the noise source make my ENR become 12.2dB? Likewise 9.3dB when adding a 6dB pad?

Yes, the attenuator serves dual purposes of lowering the ENR and also improves both ON and OFF state VSWR which increases noise figure measurement accuracy.

Formula to translate ENR at the output of the coax attenuator is much more complex than ENR_translated = ENR-Att[dB].

Papers written from NIST engineers explain well how ENR could be translated.

You also shoud consider that uncertainty related to the new ENR will be higher than the uncertainty related to the original ENR.

Added after 17 minutes:

Attached file describes how translate ENR.

Unfortunatly it is in Italian.

Cheers

Thanks. I'll take a look at it and see if Ican get a friend to translate where I need help.

Joe