Tektronix 11402 DSO - Page 1
Forum section: electronics / testgear

author: davorin
author_rank: Unknown
timestamp: June 17, 2014, 09:03:02 pm
content: I'm looking for a new DSO and stumbled upon the Tektronix 11402...Would this be a good replacement for the LeCroy 9354AL?I see the 11402 listed around US$ 500 without any modules...and with 2 * 11A71 for around US$ 700 - 800.Sad though most of them are in the US where shipping costs are almost as the value of the item (o;

author: PedroDaGr8
author_rank: Super Contributor
timestamp: June 18, 2014, 04:18:02 am
content: Quote from: davorin on June 17, 2014, 09:03:02 pmThe 11402 is an antiquated beast. Honestly, it's a very specialized instrument. It's a high bandwidth med-high resolution, very low sample rate scope. The sample rate is only 20MS/sec. This precludes it from most hobby work.

author: davorin
author_rank: Unknown
timestamp: June 18, 2014, 06:23:14 am
content: I read that somewhere with 20Msamples/sec....and made me wonder if that was a typo or not...Besides that I just saw that most high bandwidth amplifiers are 50Ohm input only....guess I rather stay with my 9354AL then (o;

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: June 18, 2014, 06:01:29 pm
content: Quote from: davorin on June 17, 2014, 09:03:02 pmJust curious: why do you want to replace it?

author: davorin
author_rank: Unknown
timestamp: June 18, 2014, 06:05:29 pm
content: Funny name you have (o;Well....looking for something with more bandwidth...especially for debugging HDMI/DVI-D signals and the like...

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: June 19, 2014, 11:55:22 am
content: Quote from: davorin on June 18, 2014, 06:05:29 pmFor some reason it was the first thing what came to my mind when registering...Yeah, I know I'm weirdQuoteI see. Since you already have a LeCroy and I guess you can live with their user interface, have you considered the LC Series (i.e. LC574A)? Should give you plenty of bandwidth (1GHz), higher sampling rate, much faster processing and a color screen. With some patience you could find one in the price range you're looking at (shipping to Switzerland from the US should be somewhat reasonable if the seller agrees to use USPS, although it can take a bit longer to arrive).

author: nctnico
author_rank: Super Contributor
timestamp: June 19, 2014, 02:09:01 pm
content: Quote from: davorin on June 18, 2014, 06:23:14 amAFAIK the Tek 11402 are intended for HF stuff looking at repetitive signals. If it comes with a plugin which goes up to several GHz it may be worth it. OTOH many of those old plugins have issues.

author: edavid
author_rank: Super Contributor
timestamp: June 19, 2014, 07:21:42 pm
content: Quote from: nctnico on June 19, 2014, 02:09:01 pmThe 11402 is a 1GHz mainframe... you are probably thinking of the 11403A, which supports the (rare) 11A81 3GHz presampling plugin.BTW a good US price for a working 11402 is $100, not $500.

author: David Hess
author_rank: Super Contributor
timestamp: June 21, 2014, 07:52:11 pm
content: Quote from: davorin on June 18, 2014, 06:23:14 amNope, that was not a typo. At the time faster sample rates were only available via CCD samplers which were used in the related DSA601 and DSA602 oscilloscopes which use the same plug-ins.QuoteThe bandwidth of a high impedance input is limited by its input capacitance. At the time 15pF was as good as they can do limiting bandwidth to about 400 MHz (25 ohms into 15 pF = 424 MHz). If you want something significantly faster, then you need to use low impedance inputs.

author: David Hess
author_rank: Super Contributor
timestamp: June 21, 2014, 08:01:40 pm
content: Quote from: PedroDaGr8 on June 18, 2014, 04:18:02 amEven back then the 11402 was intended for specialized applications rather than general design work. Unusual even for now is its 10 bit vertical resolution making it their replacement for the even older 7854. Other DSOs in the series had real time (and cutting edge) sample rates.20 MSamples/second with much faster equivalent time sampling when needed is adequate for a majority of hobby applications although I would not do without peak detection which I believe the 11402 lacks. I rarely have to bring out one of my faster DSOs in place of my old Tektronix 2230s.

author: Precipice
author_rank: Frequent Contributor
timestamp: June 21, 2014, 10:30:35 pm
content: Bear in mind it's a single ADC with 20MSA/s, and the rules for splitting that among inputs included some counterintuitive features that made it struggle somewhat, even at audio and SMPSU speeds. Definitely not a good lab scope.Also, just in case you want to use it with a 7a22 plugin to get down to anywhere near 10uV/div, be warned that the CRT scan breaks through badly in the left hand slot.I wish I hadn't given mine away, but only because I've got a low noise science product, that runs at a repetetive 33KHz - the 11402 would be good for final test on that, as it's nicely programmable of GPIB. Other than that, I'm happy to have the space back.(Note also that the 11302(A), despite having a very similar name, is a fantastically good analogue scope, probably the best Tek ever made, and it takes the same plugins. There's almost nothing else in common (except the huge size, I guess).(also also, I think that DSA601&2 don't use CCDs to downsample, they're straightforward, if brutally fast for the time, interleaved ADCs.)(Oh yeah - the 11402 would have to go on record as being utterly, completely and atrociously useless for HDMI work! (I have a spiffy DSA70604 for that sort of thing, but it's pushing the definition of 'hobbyist' a bit far, even on the used market).

author: David Hess
author_rank: Super Contributor
timestamp: June 22, 2014, 05:24:12 am
content: Quote from: Precipice on June 21, 2014, 10:30:35 pmThe 11k series was recommended to me when I inquired about a DSO mainframe which could use the 7A22 and 7A13 but I ended up with a 7854 instead. Usually I take advantage of the vertical output though on one of my other 7000 mainframes to connect the plug-in to a more modern DSO.QuoteWell, I thought it did because of the capabilities of CCD and flash ADCs at the time but you are right. The capabilities of the early TDS oscilloscopes which used CCD based digitizers look like a closer match to the DSA601 and DSA602 than the flash ADC based ones.