I am trying to use the Signal Generator to produce a 24 kHz signal so that I can tune a VLF aerial I have just built.
I have set the sampling rate on the Signal Generator to 9600 kHz and it appears to be generating a 24 kHz signal - at least there is no error message.
However, I can't see the signal on the Spectrum Analyzer. The Spectrum Analyzer shows signals up to about 22 kHz, but there is a cutoff at that point and all higher frequencies are blank.
Is this likely to be because my soundcard cannot handle frequencies above 22 kHz, or do I need to tweak the settings on the Signal Generator and/or Spectrum Analyzer? I don't know what soundcard I have as the PC came ready assembled, without any documentation.
If it is because my soundcard cannot handle frequencies above 22 kHz, will this be affecting both the Signal Generator and the Spectrum Analyzer? In other words, even if I can't detect a 24 kHz signal, will a 24 kHz signal still be output from the sound card?
if, as I suspect, it's a soundcard limitation, can anyone recommend a suitable soundcard to handle higher frequencies?
andrewlutley
Post at 22-12-2008 19:36
I guess you set the sampling rate of the Signal Generator to 96kHz, not 9600kHz.
Even if there is not error message when you set the sampling rate of 96kHz in the Signal Generator, you still need to check with your sound card's specification to see whether such sampling rate is supported or not. "...The spectrum analyzer shows signals up to about 22kHz..." was probably because you chose a sampling rate of 44.1kHz for the Oscilloscope and thus the Spectrum Analyzer will only show 1/2 of that sampling rate, i.e. 22.05kHz. Therefore you should change the sampling rate of the Oscilloscope to 96kHz or above. After this, you might still not be able to see a prominent 24 kHz signal, because many sound cards' bandwidth is limited to below around 20kHz due to anti-aliasing filtering.
Some sound cards have different behaviour with ASIO driver than with MME driver. For example, EMU Tracker Pre. With MME driver, the bandwidth high limit is around 20kHz, but with ASIO driver, it can go up to 96kHz.
virtins
Post at 24-12-2008 23:54