Hi,

I am relatively new to the spectrum analyzer world. I purchased this 141T HP spectrum analyzer (with 8553B RF, and 8552B IF) as I have been getting more into radio alignments and playing around with other RF stuff.

I have attached two photos. One of a no input signal with the centre frequency at 0. The other, is attached to the output of my Genrad 20Hz-20MHz Random Noise Generator with a centre frequency of 20MHz.

I read somewhere in the HP service manual that it is the '0Hz' marker. Although, I can't seem to find any info to back this up on the web.

Is this present on all spectrum analyzers? If so, why is it there?

Thanks in advance,

M

 

The analyser mixes the input with a local oscillator to make an intermediate frequency like a super-heterodyne receiver. By sweeping the local oscillator different parts of the input signal are converted into that intermediate frequency band and then the amplitude of that part can be displayed. So the amplitude of signals at various frequencies can be displayed. The problem is that at 0Hz from the local oscillator there is a large signal - the local oscillator itself - so that zero frequency peak will always be there.

 

The analyser mixes the input with a local oscillator to make an intermediate frequency like a super-heterodyne receiver. By sweeping the local oscillator different parts of the input signal are converted into that intermediate frequency band and then the amplitude of that part can be displayed. So the amplitude of signals at various frequencies can be displayed. The problem is that at 0Hz from the local oscillator there is a large signal - the local oscillator itself - so that zero frequency peak will always be there.

That makes perfect sense, I didn't even think about that.

Thank you for your response, I greatly appreciate it!