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Internal Ghost Signal ?

I am using a SPECTRAN 250x and have a ghost signal around 368MHz (please see attached screenshot) . Even if I change the location the signal is always present. If I switch the span to "1/2" or even smaller it works fine though. Is my unit faulty?

Ghost Signal


Your SPECTRAN unit is working fine but your CPU/USB does not catch up with the data rate. As you can see all your USB controls are YELLOW but should be GREEN. You are loosing so much data that the FFT is "breaking down" and starts to produce nonsense (your ghost signal) within the spectrum.


Use a better PC and/or check your USB connection.

You should check the USB Load (USB Overflow display) and the USB Errors graph within the SPECTRAN V6 block:

Lots of USB packages lost


If you use the same setup with SPAN ="1/2" (to reduce the data load) the FFT will work well even if you still loose a lot of packages:

FFT running with lost USB packages



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