Re: Diy oscilloscope #parts

Arv Evans

The "Transfer-oscillator" approach like Jerry suggested using an SA602 has been used
for many years to look at things that slow oscilloscopes would otherwise not see. 

Arv  K7HKL

On Thu, Feb 1, 2018 at 8:30 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Yes, it's useless for RF as is, and likely kind of ideosyncratic and of sub 200khz bandwidth.
But for $23, it's very interesting.  Gets good reviews on Amazon:

Could add an SA612 mixer, bring your transmitted signal down to 100khz
and then monitor it using the DSO138.

Page 75 of the datasheet for the STM32F103C8 used on that scope
says the sample time of the ADC when operating at 1msps is 0.107us
Could see Dexter's modulation envelope on sub 1mhz RF as a cloud of dots,
accumulating that cloud over many trigger events. 

If you had a fast sample and hold, and some way to measure time from trigger to sample, 
you could create a sampling scope.  That would be useful for RF, and could be very cheap.
One possible way to cheaply measure time from trigger to first ADC sample strobe would be counters in a 250mhz PAL,
read a count from the STM32 through an SPI interface into the PAL.  So a $3 PAL plus an STM32 and the sample and hold
gives a sampling head that effectively samples at 100mhz.   Samples after the first can be well timed, so could grab
many samples for each trigger.

Here's another possible way:  About $25 worth of parts as shown here but paired with a $2 STM32 dev board
instead of Houtman's 10mhz analog scope, gives us a 1 GHz bandwidth sampling scope.
Thinking about cheap way to do test gear is almost as much fun as
thinking about cheap ways to do ham gear.

Jerry, KE7ER

On Thu, Feb 1, 2018 at 03:29 pm, Master Ice wrote:
Be warned these scopes are of absolutely NO use for RF work.
The bandwidth is 200KHz AT BEST!
No use whatsoever for RF work.

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