Marco,
i see you still didn't got what the reason for this thread is. Ok, i will try once again. It does not matter WHAT an unknown
ideal scope, with calibrated 50R internal input is showing at rated XXX frequency - because we know this anyway from
manufacturer datasheet. The same for unknown DSO with provided probes, they almost always too cheap, they do
have almost always unknow frequency response, they didn't always matching the DSO, not always properly compensated.
And here is the point, having signal source with known level at specific Z we can measure what a DSO, with no calibrated
internal 50R temrination, is doing with this signal. For why? Well, this is the reference level (and this is exactly what you using,
not an imaginary or real value on input but what on display), a 50R teminator will be always 50R terminator, coax cable still a
coax cable (and yes there are diff, but they didn't matter on "almost DC").
And this is reference level for all DSOs then, no matter if they calibrated to 50R initernal termination or not, e.g. product A (Rigol DS1052E) will have on paper (from hardware point of view) exact the same response as product B (Agilent DS1052B).
Why ? Becuse they using exact the same hardware. The questions is, due the fact that the software might be different, are the result on screen equal as well? And same apply to majority of chinese (and as well LeCroy, Agilent low end) products.
For you, as owner of Owon, the kind of measurment is still important. You was looking for active probe, which would be then
anyway terminated external with 50R. So for you as well would be interessting to see what such probe, giving on product A such
respone (with external termination) or product B (with internal calibrated termiantion) another response, is doing on your DSO.
Btw, consider these active probe, i'm using two of them and the performance (up to ~500MHz) as as good as P6243
(i'm cheating my TEK with own eeprom):
http://welecw2000a.sourceforge.net/docs/Hardware/Aktiver_Tastkopf_mit_OPA659.pdfAnother aspect of this thread was to show kind of response, is it flat or gaussian? And here does not matter if you at DSO
rated frequency off by 1.8dB (as my test DSO), the kind of response is still the same: