My friend just ask me for the DSO203 handheld scope.Is it cheap for the DSO203,Let's talk about it.I just find a dso203 on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=271160345410&ssPageName=STRK:MESE:ITIts bandwidth isn't listed anywhere, only its sample rate, which is 36MSPS. This means that We'll be limited to 18MHz signals in theory, but in practice maybe about 5MHz. Then there is the question of the analog bandwidth of the input amplifiers, which typically needs to be bigger as well, since the bandwidth is specified by the 3db amplitude drop. Rule of thumb is that the amplitude should be 10 times the bandwidth needed.
The analog bandwidth for the DSO203 is listed as 30 MHz (and noted further by: "Analog channel circuit using unity gain >150MHz") and the sampling rate is adjustable up to 72MHz. They provide schematics if you don't believe them (I don't take much on faith, but that is what they claim and unless someone wants to model that, I have no better info). That being said, even your reply indicates use above audio frequencies, at least 3 orders of magnitude more actually.
I used to determine 36 MHz -> 5 MHz RTBW in practice. SinX/X interpolation requires a factor of 2.5. That is, a digitizer running at 36 MHz (or 18 MHz quadrature) will be suitable to provide 36 / 2.5 = 14.4 MHz of real-time bandwidth, provided suitable analog circuitry exists. Oscilloscopes often have much higher sample rates to ensure higher rate signals do not alias (3dB, which you are correct about, is not sufficient rejection).
Again, not saying this is a worse deal or a worthwhile piece of test equipment, but we really need to know Whether it is useful for us.after all,it is just a handheld oscilloscope.If you need much more function or powerful scope. you can choose
owon or
siglent brand scope.but you really need to use caution with your statements like "Its [sic] of useful ( or useless) above ___"... People just might think you are providing reliable advice.