Quote from: DreamThinkBuild on November 03, 2012, 08:31:59 AM
Hi Forest,

If you need to generate more specific frequencies I suggest Octave(which is Open Source).

http://www.gnu.org/software/octave/

Using the chirp function is a snap to generate swept frequencies or any other kind of signal. You can keep changing the parameters until you narrow down the frequency range.

Quick example:

You can also play the signal out to the soundcard directly but it depends on if your computer will recognize the command(soundsc). soundsc(OutSignal,SampleRate);

What's the maximum frequency you can get from a computer sound-card based function generator? I'd feel really cramped if I couldn't test above 50 kHz. The most basic FG that you can get these days will probably go to 2 or 3 MegaHz.... that is, 40 or sixty times higher frequency than you can get with a sound card.

Transformer / nonlinear Inductance OU simple Experiment : (and a few others)
http://ut27972.narod.ru/Book_2/109_B_2_p_109.htm


Translate with google , move to text below Fig. 2 (24)



Конвертор = Converter = Inductance
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Hi TinselKoala,

The max frequency range for some sound cards is around 20khz. A dedicated frequency generator would be better but it depends on how much Forest wants to spend.

Quote from: DreamThinkBuild on November 04, 2012, 07:58:05 AM
Hi TinselKoala,

The max frequency range for some sound cards is around 20khz. A dedicated frequency generator would be better but it depends on how much Forest wants to spend.

Most modern soundcards can sample and play at 44 kHz, but 20 kHz is generally considered to be the top end of (young) human hearing. Most adults can't hear much above 14 kHz and many can't hear above 12 kHz. Try it yourself, see where your upper limit is.
http://www.phys.unsw.edu.au/jw/hearing.html

A signal generator based on the 555 timer chip, or the TS3001 or TS3002,  and built with 20 dollars in parts would be far superior, in my opinion, to a sound-card-based system for any frequencies higher than strict audio.

http://touchstonesemi.com/products/timers?gclid=CMLdx4XotbMCFUYw4AodR3oAyQ

http://www.google.com/search?q=555+timer+signal+generator+circuits&hl=en&client=ubuntu&hs=IkP&channel=fs&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=a6KWUJ-CNYrG0AG0zoEw&ved=0CDkQsAQ&biw=1420&bih=831&sei=haKWULzmFLPD0AG1rYHQDg

My largest Tesla coil (air core certainly) has a resonant frequency of something like 80 kHz, and my smaller SSTCs generally resonate in the 300-800 kHz range. You really need to be able to go higher than audio frequencies if you are doing a lot of research involving resonance, standing waves, and VRSWR.

forest,

As an option, build one or two of these.