AnsweredAssumed Answered

Attenution settings and impact on signal

Question asked by Femtosecond on Apr 20, 2011
Latest reply on Apr 20, 2011 by tabbott
Hi there,

I have been playing with a PSA E4445A lately and noticed something weird.

I give in a signal with a certain power level, let's say -30dBm at 30MHz. The attenuation is at 10dB and it shows me exactly the 30MHz peak with -30dBm of power. When changing the attenuation now from 10dB slowly to 18dB the signal gets smaller while the PSA still tells me that the signal has a strength of -30dBm. Now, when changing from attenuation of 18dB to 20dB the signal amplitude jumps to -10dBm. It stays there until you change the attenuation from 28dB to 30dB and again it jumps back to -30dBm of power. It does the same thing when going from 38dB to 40dB and then from 48 to 50dB.

That can't be correct, can it? I often need to measure exact singal powers and with the attenuation to automatically adjust, the measured power changes all the time.

Anybody an idea how that can be?

Thanks a lot.