Re: Diy oscilloscope #parts

Jerry Gaffke
 

I'll have to look that STM32 forum over, see what they are up to.
But with the DSO138 code up on github, should be trivial to get a basic display going.
That new improved code up on github that I pointed to previously probably comes from your STM32 forum.
No need for all the op amps and switches and stuff of the DSO138 board if you know the kind of signal you want to look at,
and you might actually get 200khz of bandwidth by going around it.

For looking at RF, an SA612 mixer is probably the best bet.
Houtman's 1ghz bandwidth sampling head calls to me, and Houtman really knew what he was doing.
But that and all those other sampling techniques I suggested would be tough for most bitx owners.
To use a sampling head you need to set up a repeating signal with a good accurate trigger of some sort.

There were lots of different 602/612 type parts made in the early 1990's. 
Signetics started out with the NE602, and the subsequent NE612 was either better or cheaper depending on who you believe.
There was also an A tacked on to some of the part numbers, signifying some further improvement.
Some differences in temperature ratings.
Signetics (was NE612) got bought by Philips (renamed the SA612), and Philips got bought by NXP, further confusing things.
NXP has two datasheets up, not a nickle's worth of difference between them on page 8, and both are -40C to +85C:
    https://www.nxp.com/docs/en/data-sheet/SA602A.pdf
    https://www.nxp.com/docs/en/data-sheet/SA612A.pdf
I don't think anybody else is selling them, it's now a choice of just the above two parts.
I've heard that they are actually the same die, but that NXP still has 602 customers that insist on 602 labeling
so they don't have to qualify the new part.  Mouser sells both, the SA612A being significantly cheaper.
Cheaper is good enough for me, I'll go with the SA612A unless somebody knows more about this silliness. 

Jerry, KE7ER


On Fri, Feb 2, 2018 at 06:32 am, Michael Monteith wrote:
Jerry,
   I love the idea of using a SA612 type device to bring the frequency down.   The STM32 micro could process the signal.  Over in the  STM32 Duino Forum several people have made their own o-scope out of the device.  They even squeezed better performance as well.   I used to follow the group very closely.   But I'm using mostly ESP32 devices myself right now so haven't followed it much at all lately.

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