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

[Tim Ressel]

Actually I misspoke, I was thinking the noise signal on another 
analyzer.  The 35660 is definitely an FFT box, but I don't know if it as 
an analog section for the chirp processing. I suspect not.

Anyway it is a really great unit. If you can get one cheap it is worth 
having. That is true of a lot of HP gear. I have several old units and 
they work swell.

--TimR

On 10/28/2015 12:28 AM, rsdio at audiobanshee.com wrote:
> 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 !
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-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com