Brasshopper:
I just bought one of those cheap digital oscilloscopes. It can do some analysis, report on max and average voltage and it can also generate limited waveforms and frequencies. But better than nothing for waveform - the waves can be produced while the two channel scope is running. And the damn thing fits in the palm of your hand. Of course, you can get screenshots - the biggest issue I have is that I don't understand all of the triggering modes. Great item, poor documenation .
I was going to buy palm hand-held one, but the screen and the buttons looked too small for me. I wanted a panel I can turn knobs, and not need a toothpick to select buttons and scroll through a dozen menu's. The pocket-gizmo looks good, and I am sure it does alot - except it seemed like a companion, or portable device I would use after I actually felt comfortable using a standard one.
They also make a diy solder kit for palm oscilliscope, the screen managed to fracture somehow and is impossible for me to fix, since there's about 30 tiny wire ribbon leads on a part that probably cost as much to replace as the kit itself.
polymorph:
A 555 will not make a good VCO for a swept frequency analyzer. The output is a rectangular wave, that is heavy in harmonic frequencies. This will cause an analysis that means nothing.
Thanks for the detailed information. That's a few steps ahead of my level in understanding. I'm just now starting to learn actually how to use the 555 chip, but when I'm ready to move ahead - this information will probably be useful after I can tell the difference between a heavy harmonic frequency and ones that are not.
polymorph:
Of course, you can get sound cards that capture at 192ksps @ 24 bit, and software that can use that for a pretty good audio spectrum analyzer. Some include the ability to use one channel as an output to provide a swept sine wave, and the other as an input at the same time. Both your sound card and the software must support this.
This one looks impressive.
Cobracom - Waveguide - IW5EDI Simone - Ham-Radio
It is impressive. I tried to use that at first. I bought a little diy-kit that claimed to filter / dummy proof the signals to jack-in to soundcard software. I was able to get some signals, after a few hours wrestling with software. Then the lines looked dirty, I did not know what I was doing (and probably still don't).
The problem with that setup is, I think you would need to be experienced with a scope to know the difference between line noise anywhere, bad probe, unshielded wire, sound card or software tuning. The lines on the screen seemed messy, and I could not tell which of any part of what I was doing needed attention. It's like I needed a real oscilloscope (or experience) to compare or troubleshoot a sound card software oscilloscope.
jremington:
That scope has an FFT function. Try it.
I just found the menu for FFT, and learned how to put a red wave form on the screen that does something. I do not know what that is yet. I will look up some tutorials and figure that out, thank you.
Digital oscilloscope waveforms look messy. An analog 'scope inherently averages the signal. A cheaper digital 'scope does not. Both really have the same noise, generally, but the digital scope quantizes and captures it.
I had an older DSO that had that flaw. I recently upgraded to a newer model that includes the ability to average and weight so it looks more like an analog scope display.
Dave Jones of EEVBlog did a video about this:
OH YES Techtronix 2225 well chuffed.
Nooelec sells a much better variation of the RTL-SDR. They put a much more stable and accurate TCX0 (temperature controlled crystal oscillator) on the board and put it in an aluminum case. The original 28.8MHz oscillator is very unstable and drifty.
It is still only about $20 USD with Amazon Prime shipping.
NooElec NESDR SMArt - Premium RTL-SDR w/ Aluminum Enclosure, 0.5PPM TCXO, SMA Input. RTL2832U & R820T2-Based Software Defined Radio
