[sdiy] Cheap audio spectrum analyzer.. finally..

[rsdio at audiobanshee.com]

Thanks for the info.

There must be a different term for a "chirp" that only contains frequencies of integral multiples of the sample rate, because the standard definition of chirp is a sweep over a continuous range of frequencies. The latter kind even occur naturally in audio-frequency radio waves.

Brian


On Oct 27, 2015, at 10:25 PM, Tim Ressel <timr at circuitabbey.com> wrote:
> Quite sure. The chirp was generated using an inverse FFT. This ensures there is energy only in the FFT buckets, thus preventing the spill over you usually get with FFTs.
> 
> On 10/27/2015 9:51 PM, rsdio at audiobanshee.com wrote:
>> Are you sure it's using an FFT in that mode? As the videos show, it's possible to do the whole process in the time domain. If the scope has a rectifier mode, you'd get a clean line instead of a solid shape for the envelope.
>> 
>> Brian
>> 
>> On Oct 27, 2015, at 12:10 PM, Tim Ressel <timr at circuitabbey.com> wrote:
>>> I have used the 35660 extensively. It is an excellent box for its age. It has a mode where you feed a chirp through the DUT and it magically smooths out the FFT results and gives a clean line. Very nice!  Wish I had one.
>>> 
>>> On 10/27/2015 10:28 AM, Jean-Pierre Desrochers wrote:
>>>> I finally decided to go for this:
>>>> 
>>>> HP 35660A (with option 001 memory installed)
>>>> http://www.sglabs.it/public/SgLabs_HP%2035660A.pdf
>>>> 
>>>> It was not cheap but around one third of eBay's mean prices
>>>> for those working condition HP testers..
>>>> and the dealer was 1 hour car ride from my home.
>>>> I think it's a good investment.
>>>> Ooooff !
>