Advantest R3465 Spectrum Analayzer Showing Funny Business at DC and Below

[Mechatrommer]

i just got my Advantest R3465 Spectrum Analyzer, after some repair and replacement, i think its good to go, except one thing. the SA showing -13dB at DC. has it got something burnt inside? a DC block maybe? and another thing is, whats funny about this scope is that it can show you down to -200MHz signal, i repeat, negative frequency folks, with some images from positive side (30MHz CAL output in this case). see attached picture. whats going on? the FW broke or something? or it is just the way it is? Waiting your reply thanks.

[nctnico]

I see nothing out of the ordinary here.

[Mechatrommer]

I see nothing out of the ordinary here.

so your Advantest R3477 is showing the same thing?

[nctnico]

I see nothing out of the ordinary here.

so your Advantest R3477 is showing the same thing?

I can give it a try to make sure but I'm 99% certain all the Advantest spectrum analysers I've owned showed the same behaviour.

[BravoV]

Congratz on the score. 

My recent scored Korean SA NS-30, if I entered the span wider than the (center freq X 2) , it will automatically correct it either starting from zero (bumping left), or at max bandwidth 3 GHz (bumps on the right).

If that behavior is normal for Advantest, than that is indeed strange.

Sub MHz range normally is high noise, hence the high peak you saw.

You should do something about the SA's date Pakcik. 

[nctnico]

I just checked: my R3477 has exactly the same behaviour.

[Mechatrommer]

thanks nctnico for the confirmation. yes BravoV its strange that Advantest left this behaviour to the SA, its specified as 9KHz minimum, even though its within specification (have to set RBW small enough) it can be sometime confusing. peak search also not working as the marker will be directed to this 0MHz mirage if i probing less than -13dB signal. i need to shift span to exclude this madness. and congratulation for your score too, cheers and selamat.

[michael_liu4444]

The spectrum shown at "0 Hz" is what we called  "LO Through". Some new generation SA has "LO Through Supress" function. With this function,  LO Through on display will be much lower. If your R3465 does not have this function designed inside its circuit,  this high "LO Through" on display should be normal.

Sent from my SM-N950F using Tapatalk

[michael_liu4444]

i just got my Advantest R3465 Spectrum Analyzer, after some repair and replacement, i think its good to go, except one thing. the SA showing -13dB at DC. has it got something burnt inside? a DC block maybe? and another thing is, whats funny about this scope is that it can show you down to -200MHz signal, i repeat, negative frequency folks, with some images from positive side (30MHz CAL output in this case). see attached picture. whats going on? the FW broke or something? or it is just the way it is? Waiting your reply thanks.

The spectrum shown at "0 Hz" is what we called  "LO Through". Some new generation SA has "LO Through Supress" function. With this function,  LO Through on display will be much lower. If your R3465 does not have this function designed inside its circuit,  this high "LO Through" on display should be normal.

Sent from my SM-N950F using Tapatalk

[0culus]

It's normal behavior in a sweep tuned analyzer, as others have surmised.