Q1  If my GFG8255A fuse burns out, how do I replace it? 
If the fuse is burned out, the instrument will not operate. First find out the cause of the fuse damage and correct it, then replace it with the correct value and type of fuse, as shown in the following list:
Model 
Fuse values and types 
Input value 

115V 
230V 
Watts 
VA 

GFG8215A 
T 0.315A 250V 
T 0.16A 250V 
22 
28 
GFG8216A 
T 0.315A 250V 
T 0.16A 250V 
25 
32 
GFG8217A 
T 0.315A 250V 
T 0.16A 250V 
27 
34 
GFG8219A 
T 0.315A 250V 
T 0.16A 250V 
29 
36 
GFG8250A 
T 0.315A 250V 
T 0.16A 250V 
25 
32 
GFG8255A 
T 0.315A 250V 
T 0.16A 250V 
29 
36 
Note: To prevent danger, be sure to replace the 250V fuse and cut off the power supply before replacing it.
More Porduct information: Spectrum Analyzers
Q2  How to understand that time domain and frequency domain are two sides of a signal? 
A ridge across, a peak sideways; far, near, high, low, no shapes alike; one can’t see Mt. Lu’s true nature; since one is in the mountain. Written on the Wall at Xilin Temple by Su Shi.
I believe that electronic engineers should have the same feeling when learning signals. The more they learn, the less they understand.
Time domain, frequency domain and modulation domain just observe signals from different aspects.
Taking FSK as an example, what you see in the time domain is a sine wave with frequency changes, what you see in the frequency domain are two frequencies (ideally), and what you see in the modulation domain are changes in High and Low digital information.
The signal jitter seen in the time domain is phase noise in the frequency domain.
To observe the frequency domain on a time domain oscilloscope, you can use FFT (Fast Fourier Transform).
To observe the time domain on a frequency domain spectrum analyzer, you can use the Zero Span setting. The amplitude dynamic range of a spectrum analyzer is wider than that of an oscilloscope, which is suitable for viewing large and small signals at the same time. It can provide better amplitude resolution and accuracy when measuring signal and noise amplitudes simultaneously.
Therefore, to reveal the true nature of the signal, we can observe it from these three aspects (time domain, frequency domain, and modulation domain).
More Porduct information: Spectrum Analyzers
Q3  What are the basic differences between a Spectrum Analyzer and an Oscilloscope? 
If we use the three axes of time, frequency, and amplitude, we can define three domains.
The spectrum analyzer is an instrument representative of the frequency domain (the relationship between frequency and amplitude). The vertical axis of the display is amplitude (power) in dBm, and the horizontal axis is frequency in Hz.
The oscilloscope is an instrument representative of the time domain (the relationship between time and amplitude). The vertical axis of the display is amplitude (voltage) in V, and the horizontal axis is time in S (seconds).
Digital oscilloscopes can convert time domain signals into frequency domain through fast Fourier transform. However, due to the insufficient vertical dynamic range of oscilloscopes (usually 8 bits), spectrum analyzer is still required to accurately measure the amplitudes of harmonics and noise.
Modulation domain analyzers (Modulation domain) display the relationship between time and frequency. Frequency counters with fast measurement speed can depict modulation domain waveforms through computers. Spectrum analyzers or the advanced FFT of oscilloscopes also have the function of displaying time and frequency.
More Porduct information: Spectrum Analyzers
Q4  Spectrum Analyzer Rack Mount Kit 
GRA415 Rack Mount Kit for GSP9330 and GSP9300B
Q5  What regulations do I need to meet signal receiving equipment used in testing EMI? 
 ±2dB absolute amplitude accuracy
 Filter (6dB) that meets CISPR requirements, as shown in the table below:
Frequency band 
Filter (6dB) 
9k ~ 150kHz 
200Hz 
150kHz ~ 30MHz 
9kHz 
30MHz ~ 1GHz 
120kHz 
1GHz ~ 3GHz 
1MHz 
 Support Detector for EMI: Max Peak (PK+), QuasiPeak (QP), EMI Average (EMIAVG), RMS Average (RMSAVG)
Q6  Why can't spectrum analyzers or EMI receivers observe transient interferences of electrostatic discharge? 
Q7  What is the QP time constant defined in the CISPR 16 Regulation? 
Q8  Can GSP9330 set a Limit Line of CISPR 25, a Limit Line with breakpoints? 
Q9  Does GW Instek have EN55025/ISO16750 automotive conducted EMI test kit? 
Q10  Which power cable should I use for EMI testing? 
Q11  Noise difference between Common mode and Differential mode. 
Common mode and differential mode noise 
Q12  What is the timing of using Transient Limiter GPL5010? 