Spectrum and Power mode in HF-4040
I have a HF-4040 device for two weeks and I need some help with the following situation. Namely, the device HF-4040 is supplyed directly with signal strength -30 dBm (SPECTRAN is directly connected to the RHODE AND SCHWARZ Mobile Tester SMFP 2). In power mode, the incomming power is accurately displayed. But when I go in the spectrum mode, the display unit start showing values between -70 and -75 dBm and sometimes goes up to -120 dBm. I do not understand why this is happening?? I thought that detected signal strenght must be the same, no matter in which mode SPECTRAN HF-4040 works. Also, when I disconnect HF-4040 from Testre SMFP 2, in power mode it detect strenght -48 dBm, and that is OK, becouse sensitivity of the HF-4040 in Power mode is -50 dBm. But, when I switched to the Spectrum mode (device still disconnected) it shows the same valuse between -70 and -75 dBm...What is happening??
Otherwise the device Mobile Tester SMFP 2 is set to work on the frequency of 305 MHz with strength -30dBm, and the HF-4040 has the following settings:
Center Frequency: 305 MHz
RBW: 100 kHz
VBW: 3 MHz
SPTime: 10 ms
Reflev: 10 dB
Range: 100 dB
You might have a heavily modulated or pulsed signal which the unit cant detect (a much longer sweeptime might help detecting it) or the frequency is simply wrong. In that case you should change from zero span to sweep mode to finde the signal / right fequency.