Hi all. I have an old signal generator (HP 8656B) that only goes down to -127dBm. However, I would like to do measurements at lower levels than this, down to maybe -137dBm. Can I just connect a 10dB attentuator to the output of the signal generator and then subtract from the output power shown on the display? Seems like I can, but maybe its not that easy.
Thanks!!!!!!!!!!!!! Ben
That depends a lot on the signal generator itself and the integrity of its case and shielding. You will definitely get additional attenuation, and the attenuator steps on the signal generator should remain accurate. Your additional attenuation may be slightly less than 10dB, however, due to leakage.
I guess the real question is how accurately must you know the absolute output level? For that matter, how accurate is the generator output level now at -127dBm?
Chuck
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It is that easy if the load you are driving approximates 50 ohms resistive.
Jim
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That unit goes up to 2 GHz (according to my Internet search). At higher frequencies, shielding becomes tricky. You can add attenuation but might face leakage paths.
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