An old video, but still very relevant, thanks! I thought I knew about zero-span, but what I was thinking of was setting the tracking generator to zero span, but that's a different thing all together.
I have a question. In the zero-span mode is the center frequency the oscillator local frequency of the first conversion stage? Or is the frequency of the IF filter of the last conversion stage?
In most spectrum analyzers, there are a few conversion stages, thus there are a few local oscillators. Each of these is adjusted so that the signal of interest (at the measurement frequency) land in the subsequent IF stage.
so for an AM case, we can say that, the message/modulated signal power is changing over time in the frequency domain? While the carrier power is constant in the frequency domain? Sorry for asking, I have limited knowledge of communication haha...
Hi, I have a question, who did you configure the trigger??, because I couldn't see the same response that you, and I thought that this was my problem, thanks
I'm sorry - I did this video 10 years ago, and I no longer have this analyzer, and I can't remember specifically where the video trigger control is on this unit.
I am still confuse, if the power in the sideband doesn't change, that means the sum power of the carrier and sideband is a constant right. So why does it varies?
I have a doubt, and don't know if i'm right or fail. I have an HP service monitor, the 8924C, it have a spec an but if offers not "zero span", in best case have 50KHz span, but not zero span, but late as show your video i see as the spec an acts as an scope in the X axis taking time as scope's sweep does. In my case i've used to show the modulated signal with the scope the 8924 have and i take the same result as you show in the vid, so i can mean that the spec an act as scope in zero span. Is it right, o wrong? (sorry, my english is not so good)
trill4kill Yes, zero span is like an oscilloscope, except that the vertical axis is driven by the output of the RBW and detector instead of a broadband vertical preamp. I am not familiar with your service monitor, but most service monitors have a way to display AM demodulation, which is nearly the same thing as zero-span.
Changing the SPAN will also typically change the resolution bandwidth (RBW), which can change the signal amplitude, depending on the type of signal. It is not a malfunction.
With slope tuning FM signals, I find that the Gaussian shape of the RBW filter mirrors the Log amplitude processing better. With AM signals, Linear amplitude processing is best.
Yes, what I want to ask is since the zero span measurement measures the power under RBW over time, this indicates that the power of the two sidebands changes over time since they contribute to the sine wave in the zero span, right? If the RBW is reduced such that the area under RBW only includes the carries, the power on the zero span is constant since it only measures the carrier power right? Thanks.
Hi...I hate to barge in on you here..it is a very nice video...can you tell me what would cause a Tektronics 2431L controls to be extremely jumpy or sensitive to use...again sorry for barging in..I did not know how or where to ask you...
What it means is that there's really no such thing as "zero span" spectrum analysis. "Zero span" is just an established slang term for time-domain single-frequency power charting. It is not related to spectrum analysis at all, it is basically a regular oscilloscope functionality.
True - a zero span display on a spectrum analyzer is NOT a spectrum result. It is a time-domain plot of the detected power within a given bandpass filter (RBW) which is centered at a given frequency (center frequency). It is not exactly "regular oscilloscope functionality" since a scope would show you the actual sampled RF signal/carrier/etc. It is more akin to a scope looking at the output of a power detector that is following a bandpass filter centered on the frequency of interest. In some sense, FFT and DFT based signal analyzers can be thought of as zero-span analyzers in the sense that when measuring a span that is
I have a question: I am trying to measure the power of an unmodulated signal on a certain frequency with 100 ms time intervals. For example i will take first power value at 0 ms then i will take the second at 100 ms...etc. Is zero span help me on this measurement? Thank you,
şeyma tütüncü Yes, you can use zero span to make this measurement. Make sure the center frequency is set to your signal frequency, and adjust the horizontal time scale as needed. Use markers to measure the amplitude at your desired intervals.
