[Premium-Rx] OT: Owan or Rigol scopes

[GandalfG8 at aol.com]

In a message dated 23/02/2013 05:33:58 GMT Standard Time, Ka9p at aol.com  
writes:

Apologize for the OT bandwidth but thought this might be a decent  chance 
to 
get an unbiased opinion or two as my 466 Tek is starting to  fade.

Has anyone experience with the lower end Owan or Rigol scopes? I  generally 
 
read ok reviews but then every once in a while read an  opinion that sounds 
 
pretty bad.

I would just be using the  scope for routine radio fixing.

Thanks  Scott
______________________________________________________________
   
Hi Scott
 

I've got a Rigol DS1052E 50MHz scope, bought a few years ago and converted  
to 100MHz via a firmware upgrade, and also a more recent Owon SDS7102 
100MHz  scope.
 

Both seem to be good general purpose scopes although if buying  now the 
Owon would be my preference.
Not only does it have an 8 inch display, makes it much nicer to use, but  
online comments suggest that Rigol used interleaved and overclocked multiple 
A  to D convertors to achieve the specified bandwidth whereas the Owon, 
being a  more recent design, uses more modern devices without such trickery.
Rigol may also have more recent models now but I have no experience of  
these.
 

I've seen pictures of these scopes displaying complex video waveforms, not  
something I've tried, and they're both great on things such as displaying  
individual short pulses with low PRF, the few uS wide 1PPS from a GPS module 
for  example, which can often give analogue scopes a headache, as well the 
usual  straightforward sine waves etc.
 

However there are some things that do confuse both of them, so I'm assuming 
 this is more to do with limitations of digital scopes in general, or 
cheaper  ones anyway, rather than something specific to individual scopes.
 

Example 1, a 10MHz sine wave from a sig gen displays fine, as would be  
expected, on both of these as well as on a TEK 2224 60MHz analogue scope.
A 10MHz sine wave AM modulated to approx 30% with a 1KHz sine wave will  
also display fine on all three scopes if looking at the 10MHz carrier but 
whilst  the modulation envelope can be displayed on the TEK, a bit tricky to get 
fully  locked but even when drifting looking just as one would expect, both 
digital  scopes have problems with this and whilst it is possible to lock 
onto the  envelope what's seen is certainly not correct, more like a carrier 
modulated  with slight ripple than to a depth of 30%.
 

Example 2, a Dynamic Sciences I-1700 Impulse Generator, as used for  
amplitude calibration of surveillance receivers, is set to output  a levelled 
amplitude narrow pulse, of approx 2V, at a 1MHz PRF.
1MHz was chosen as the TEK displays this fine, both individual pulses and  
also as a levelled amplitude pulse stream, but individual pulses, as would 
be  expected, start to become less distinct on the TEK at PRFs of 100KHz and 
below  when displaying them as a stream.
Both digital scopes will lock on to individual pulses but both have  
problems displaying the pulse stream and they seem to apply their own modulation  
envelope, best way I can describe it, which displays packets of pulses with  
varying amplitude. The effect varies with time base setting, even reverting 
to  displaying single pulses again as the time becomes longer. The Rigol 
definitely  seems worse on this one than the Owon, so perhaps dependant on the 
input  sampling method, but both could give the impression that something 
was seriously  wrong with the I-1700 if I hadn't got the TEK to fall back on.
 

I'm sure there's good explanations for the above, in terms of aliasing or  
transform theory or whatever, but I certainly don't have time to  
investigate the theory every time a display seems a bit suspect.
 
So whilst I'm very pleased with both digital scopes, and the Owon in  
particular, and certainly don't regret buying either, I've had to drop my  
original intention of replacing the TEK with something smaller and lighter as I  
obviously still need it if only for the occasional confidence check.
 

Regards
 

Nigel
GM8PZR