Which oscilloscope to select? - Page 1
Forum section: electronics / testgear

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 21, 2014, 12:00:49 pm
content: Hi! I am setting up my own lab and I have recently built my workbench.I would like to get a Rigol oscilloscope. I was thinking of getting the DS1104Z-S or the DS1204B.These are 4 channel oscilloscopes. Can anyone tell me what the bandwidth defines?I probably will work to a variety of projects and probably in the satellite communications domain.Thanks

author: newbe
author_rank: Newbie
timestamp: January 21, 2014, 12:29:31 pm
content: Quote from: Alexandros81 on January 21, 2014, 12:00:49 pmBasically, the bandwidth defines which satellite you'll be able to communicate with, and which not.

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 21, 2014, 04:47:54 pm
content: I mean what the bandwidth of an oscilloscope defines?

author: z01z
author_rank: Regular Contributor
timestamp: January 21, 2014, 05:20:23 pm
content: Google is your friend:first hit.

author: BravoV
author_rank: Super Contributor
timestamp: January 21, 2014, 05:33:35 pm
content: Just curios what kind of satellite communications you're working on since you're not aware of what a scope bandwidth is ?For sure its not about the satellite's wireless signaling right ?

author: electronics man
author_rank: Frequent Contributor
timestamp: January 21, 2014, 06:06:27 pm
content: I would recommend the ds1000z-s it is a very good scope. And the band width is the frequancy at witch the amplitude of your signal is 3Db down so it means eg a 70Mhz signal on a 70mhz scope will be attenuated by 3Db. So it just means you can measure higher frequancy than you bandwidth but it will be badly attenuated.

author: w2aew
author_rank: Super Contributor
timestamp: January 21, 2014, 09:50:39 pm
content: Quote from: Alexandros81 on January 21, 2014, 04:47:54 pmHere's a few videos on oscilloscope bandwidth:and...

author: EPAIII
author_rank: Super Contributor
timestamp: January 25, 2014, 02:46:02 am
content: The quick answer is the bandwidth for an analog scope is generally given at the 3db down point. That is the frequency where the response of the vertical channel is 3db below the response at low frequencies. That translates to 50% of the low frequency level.This is not a real useful point on the frequency curve to be operating at if you need any kind of precise measurement because, due to component tolerances, this is a guaranteed spec. for that model, but not an exact number for any individual scope. Individual scopes with the same model number may have gains that differ by a fairly large amount at that specified frequency. So, unless you run an actual calibration curve on your particular scope, you really have to assign a fairly large margin of error at that frequency. Hence a 100 Mhz scope may become inaccurate when you get above 25 or 50 Mhz.Personally, I would rather see a spec where the gain is guaranteed to be within 5% or even 1% of the low frequency value.

author: echen1024
author_rank: Super Contributor
timestamp: January 25, 2014, 03:46:20 am
content: I can vouch for the DS1074Z. I did not buy the "-S" version though, since Agilent decided to donate me a function gen, and if you want, watch my review videos on the DS1074Z. Be advised, the teardown will make your eyes fall out of their sockets and make your glasses shatter into a million pieces.

author: BravoV
author_rank: Super Contributor
timestamp: January 25, 2014, 03:52:40 am
content: Seems people that offer help here are ignoring the original request here, don't you guys have any clue what a "minimum" bandwidth for satellite communications related work ?The suggested sub US$1000 scopes are a toy in this area.

author: echen1024
author_rank: Super Contributor
timestamp: January 25, 2014, 04:03:27 am
content: The go from 100 MHz to over 2GHz. That means the OP had better invest in something like a Tektronix TDS694.

author: BravoV
author_rank: Super Contributor
timestamp: January 25, 2014, 04:34:13 am
content: Quote from: echen1024 on January 25, 2014, 04:03:27 amNope, not even close, just google for satellite bands/frequencies ranges.Remember, say for observing a 1 GHz signal, a 1 GHz scope just won't cut it, you need higher bandwidth.

author: electronics man
author_rank: Frequent Contributor
timestamp: January 25, 2014, 05:12:42 pm
content: Agilent 90000x might cut it for you but you need a massive wallet to afford it.

author: ConKbot
author_rank: Super Contributor
timestamp: January 25, 2014, 05:49:38 pm
content: Quote from: BravoV on January 25, 2014, 03:52:40 amThe bandwidth range is so broad that speculating on what he's doing would be just as unhelpful. some satellites operate at or above Ka band (27-40 GHZ)And even if its not that high, for RF and coms work a scope is hardly ever the right tool.

author: BravoV
author_rank: Super Contributor
timestamp: January 25, 2014, 06:14:39 pm
content: Quote from: ConKbot on January 25, 2014, 05:49:38 pmI guess so, also sort of hinting out the suggested replies are basically useless, and clearly the OP doesn't know what he doesn't know.Just read my previous post #4 to get a hint, and also I happened to remember few of his threads asking questions cause they'reoverly ambitious...err... memorable.