Unusual spectrum plot with the lowest RBWs

Realtime Remote Spectrum Analyser PC Software for MAC OS, Linux and Windows

Unusual spectrum plot with the lowest RBWs

Postby MauroD » Wednesday 24. October 2018, 22:34

Hello people, I got the spectrum plots which are shown in the images with an Spectrum HF-60105 V4 X device. This device was bought with the options 020 (preamp) and 002 (0,5ppm TCXO Time Base). I connected a 50ohm load at the input to see the sensitivity I can get with the lowest RBW (200 Hz with option 002). The difference among the images is the span and RBW. I cannot understand why a band with a lower power appears in the middle of the plot when I choose the lowest RBWs, 200 Hz to 1 KHz, with a span bigger than 200 KHz. The band's lenght is 200 KHz when RBW is 200 Hz, and a little bit more when RBW is 1KHz. In one of the images I changed the RBW to 10 KHz and the band dissappeared. And in another image I changed the span to 200 KHz (with RBW 200Hz), to only see that band, but a peak appeared in the middle of the plot. :?:
Have someone got the same results? Is it something normal? Can you help me to understand this phenomenon?
espectro extraño_4.png
espectro extraño_3.png
espectro extraño_2.png
espectro extraño.png
Posts: 8
Joined: Friday 21. September 2018, 00:20
Location: Argentina

Re: Unusual spectrum plot with the lowest RBWs

Postby mm_dev » Monday 5. November 2018, 15:22

Certain frequencies that are multiples of 10/20 MHz are sensitive to internal interference from the device as you can see in your third image. The MCS has a feature called "Peak Suppression" to eliminate those fake signals. As different combinations of sweep parameters influence the amount of interference this can sometimes look a bit strange like in your second and fourth picture as the generated fake noise doesn't match the real surrounding noise.

You can disable the "Peak Suppression" feature in the Extras menu.
Posts: 285
Joined: Wednesday 4. May 2011, 07:43

Return to MCS

Who is online

Users browsing this forum: No registered users and 6 guests