EEVBlog #1103 - Omicron Labs Bode 100 Review & Experiments - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: July 09, 2018, 11:15:04 pm
content: Review of the Omicron Labs Bode 100 50MHz Vector Network Analyser / Frequency Response Analyser and some experiments measuring bypass capacitors and characterizing a quartz crystal.https://www.picotest.com/products_BODE100.html

author: sibeen
author_rank: Frequent Contributor
timestamp: July 10, 2018, 06:19:07 am
content: Omicron just makes nice gear. I'm quite familiar with their protection relay testgear. That comes in at least 10x the cost of the Bode but for what it does it is worth it.

author: PA4TIM
author_rank: Super Contributor
timestamp: July 10, 2018, 09:14:12 am
content: Nice to see more network analysis stuff. This is a nice peace of kit and seeing you get usable results without ( i think) working through the manual and many, many hours practice, the software must be user friendly.VNA's are great for impedance around 50 ohm. For very high or very low impedance you use IV measurements (impedance meters/analysers use that) and for some VNA's (like the SDR-kits VNWA) there are adapters to do that. The software needs to support that (like the VNWA does) if you do not want to do the math. I did that once just for fun with a 1968 build HP VNA (the ESR of a 1nF cap) See the attached photo. But there are also tricks like measuring a 100 K resistor parallel to a 50 ohm or a 0,001 ohm in series with a 50 ohm. The 50 ohm can be your cal load or just measure it, a 50 ohm resistor can be measured extremely well with agoodcalibrated VNA. In both cases I use the custom trace function so I do not need top do the math.I would expect the Monicron supports IV measurements in the bodeplot function and "normal" wave parameters for the VNA part ?Dave, the results of a vna are at the best as good as the calibration.This is often a rather time consuming thing and needs a very good calkit (a male and a female based kit and then the things you used fort that fixtures) and very advanced software implementation to do n-term error corrections. That is why VNA's have very extensive calibration functions and things like de-embeding and port extension functions. Even a hobby VNA as the SDR-kits VNWA can do that. I missed that in your review.Are the fixtures and their cal-kit parts already characterized in the software ? I would expect a cal certificate with the numbersThe resistor value does not have to be a precision one, as long as you know the resistance and are able to tell that to the VNA. Things like open and short are more important (OK, for 0-50 MHz probably everything will do) I use my SDR-Kits VNWA often in the span 1 KHz tot 10 MHz and calibration there is not really a big thing. Above 500 MHz it becomes the most important part of the measurement.I like the fact it can make bode plots and do s-parameters, that combination is very nice.The DUT fixtures look cheap if you compare them with the keysight ones. But I do not know the prices from those, probably much higher.http://literature.cdn.keysight.com/litweb/pdf/5968-5329E.pdfthis pdf tell a lot about the things to know when using fixtures.When I started playing around with VNA's there was almost no information for non RF graduated EE's That is why I made a series of tutorials. They are not flawless but I tried to make it easy to understand and for most practical. I used the SDR-kits VNWA for it, back then more or less the only choice.For those who are new in this field, check them out, they are free pdf's.http://www.pa4tim.nl/?p=1594All in English and some are translated in French and German by other VNWA users.Keysight has a free PDF, the impedance measurement handbook.https://literature.cdn.keysight.com/litweb/pdf/5950-3000.pdfvery interesting and "easy" to understand

author: timgiles
author_rank: Regular Contributor
timestamp: July 10, 2018, 12:02:17 pm
content: Thanks Dave - great first video - looking forward to the others. Flexibility looks off the scale.

author: Smokey
author_rank: Super Contributor
timestamp: July 11, 2018, 11:28:30 pm
content: https://www.eevblog.com/forum/eda/bode-plots-come-from-hendrik-bode-who_s-name-is-pronounced/... Just saying...

author: Wolfgang
author_rank: Super Contributor
timestamp: July 12, 2018, 04:19:31 pm
content: Hi,I would say that the creation of cal kits is a very tricky task in the GHz region, but not really at 50MHz where the Bode 100 is operating. I have made a lot of cal kits for ham radio use, and I calibrated them by comparison with a Keysight E5071C using a Keysight eCal module. Below 100MHz 30dB or better can be reached even with homebrew open, shorts and loads. Even leaded components could be used.The accessories that come with the Bode 100 are all made using very classic construction techniques and no Gigahertz trickery. Everything more seems to be luxury.

author: Bud
author_rank: Super Contributor
timestamp: July 12, 2018, 04:43:53 pm
content: The isolation transformer seems to use a regular Hammond type aluminum cast enclosure. Perhaps $8 a piece or something. The main unit seems to use a standard enclosure as well. Nothing against it in terms of performance but I'd think for the selling price something custom could be made to stand out better.

author: jancumps
author_rank: Unknown
timestamp: July 12, 2018, 05:17:01 pm
content: Quote from: Bud on July 12, 2018, 04:43:53 pmDo it

author: envisionelec
author_rank: Frequent Contributor
timestamp: July 12, 2018, 05:41:14 pm
content: As I mentioned in another, similarly named thread, I broke down the entire BOM and came up with about $110 for a single unit. I'm building one and will characterize it - then probably start selling them because, why not?

author: Wolfgang
author_rank: Super Contributor
timestamp: July 12, 2018, 05:45:14 pm
content: Much luck ! IMHO you will be able to reproduce the hardware, but all the software and GUI is another story. This could well be a few mythical manmonths minimum ...

author: jancumps
author_rank: Unknown
timestamp: July 12, 2018, 05:54:04 pm
content: Quote from: Wolfgang on July 12, 2018, 05:45:14 pmThis. And the promise that you will be available when something is wrong. And the design work that you do not have to earn back. And the samples that you don't have to send to Australala...

author: Brumby
author_rank: Unknown
timestamp: July 13, 2018, 03:28:52 am
content: Quote from: jancumps on July 12, 2018, 05:54:04 pmLa la land is on the west coast of the USA.

author: EEVblog
author_rank: Unknown
timestamp: July 13, 2018, 06:48:35 am
content: Doh!I complete missed the AD834 multiplier in the receiver can.The part number wasn't really visible direct on

author: Kleinstein
author_rank: Super Contributor
timestamp: July 13, 2018, 07:03:58 am
content: Using that analog multiplier is kind of a surprise: Its an expensive part and helps to reduce spurious signals due to harmonics of the LO. However its also limited accuracy and stability. So the 24 Bit ADC used later on does not make that much sense anymore. At least the analog multiplier (likely as a mixer) reduces the need for filtering. So maybe they use some of the CMOS switches for the possibility to do extensive internal adjustment runs to compensate for the limitation of the analog multiplier. It does not even look like they could bypass the AD834 for the low frequencies, where there is no absolute need for a mixer.

author: EEVblog
author_rank: Unknown
timestamp: July 13, 2018, 07:07:08 am
content: Photos are up:https://www.flickr.com/photos/eevblog/albums/72157669079722607

author: Kleinstein
author_rank: Super Contributor
timestamp: July 13, 2018, 07:20:09 am
content: Ups - I think the last few posts should have gone to the tear-down thread and not here.

author: JS
author_rank: Frequent Contributor
timestamp: July 13, 2018, 08:46:20 am
content: Looks like so, I ended up here as someone mentioned in the other post...JS

author: Berni
author_rank: Super Contributor
timestamp: July 13, 2018, 09:12:23 am
content: Sweet bit od kit. The price point might be a bit steep, but dang does that software look good. It does exatly what its suposed to without exesive messing about, setting stuff, reading manuals etc. If only otger test gear came with software that us even half as good as this.Seing a mutiplier makes perfect sense to down convert to an IF that the ADC can sample, and we can make very very nice ADCs for 100KHz due to audio. Mixer harmonics can be compensated for with calibration and the 24bit ADC gives you exelent dynamic range(they are not too expensive ether)I do have a Agilent Vector Signal Analyzer that does DC to 10MHz with similar capability(signal gen, dual input) but the software is simply not there to do much more than gain/phase and spectrum analysis(tho has exelent dynamic range). It could do all this can do too with some extra test fixtures, but i neved had a big enugh need to make such software using GPIB, nor would it be anywhere near as nice as this.

author: Alextsu
author_rank: Contributor
timestamp: July 14, 2018, 07:15:12 am
content: Thanks for this post, Dave!If anyone would try to re-eng the input receiver channel schematics, or have some ideas how to build one, please, share.Couldn't afford such an expensive FRA, but would like to try to make something similar for homelab.

author: EEVblog
author_rank: Unknown
timestamp: July 14, 2018, 07:49:40 am
content: Quote from: Berni on July 13, 2018, 09:12:23 am+1

author: Kleinstein
author_rank: Super Contributor
timestamp: July 14, 2018, 11:55:43 am
content: Quote from: Alextsu on July 14, 2018, 07:15:12 amThe first half of the receiver part should be similar to an scope input stage, and a few extra switches to choose between the input and an internal cal signal / the source. For the rather low frequency range a simple mixer, some AA filtering (not that much with an SD-ADC) and that the good resolution ADC could be all it takes. A difficult part would be to get a well defined frequency response for all gain settings - because of this I would prefer to have some of the gain switching behind the mixer. 50 MHz is not that high in frequency, but a IF in the 10 kHz range is even easier to handle. Both Channels seem to share a single LO that is likes driven from the same master clock. For a low cost version I would imagine one could get away with a switching mixer, maybe CMOS switches.There are a few DIY VNA projects around, that also use DDS chips and high resolution ADCs - as the software is about the largest part of the project, it might be easier to start with such a circuit so that maybe one could have a start on the software. It may take changes with the input stages to go all the way to the DC coupled range.The other alternative would be something like the red pitayar or analog discovery HW, using the faster ADCs and direct sampling. This common HW might help to find some open source SW, at least for a start.

author: voltsandjolts
author_rank: Unknown
timestamp: July 14, 2018, 12:58:44 pm
content: I realise the Analog Discovery has nowhere near the breadth of capability the Omicron has but it would be interesting to see a few comparisons.Does the Analog Discovery FRA give comparable results, at least within it's comfort zone?

author: Bud
author_rank: Super Contributor
timestamp: July 15, 2018, 01:58:16 am
content: Quote from: Kleinstein on July 13, 2018, 07:03:58 amIt is a delta sigma ADC, this type of ADC typically have hardware very narrow band selectable digital filter, which greatly reduces requirements for external analog filters. This comes at the expense of increased conversion time though.

author: Bud
author_rank: Super Contributor
timestamp: July 15, 2018, 02:00:47 am
content: Quote from: jancumps on July 12, 2018, 05:17:01 pmSorry do what?

author: Bud
author_rank: Super Contributor
timestamp: July 15, 2018, 02:02:44 am
content: Quote from: EEVblog on July 13, 2018, 06:48:35 amWhat are your guesses why MELF resistors were used?

author: Bud
author_rank: Super Contributor
timestamp: July 16, 2018, 05:29:29 am
content: Mouser and Vishay singing audiophile praise to MELF resistors, with the familiar "no distortion" thingie.Quotehttps://www.mouser.com/blog/reating-a-sound-people-cant-resist-melf-resistors

author: Kleinstein
author_rank: Super Contributor
timestamp: July 16, 2018, 07:56:37 am
content: Form the color code those resistor seem the be 5.1 K and 1 K with 0.1% tolerance. They might be used for there low tolerance, maybe in a kind of differential amplifier between the AD834 mixer and the ADC.Compared to smaller SMD resistors the MILF form factor might offer a slightly better excess noise because more resistive material is used, though I doubt this would be a factor here.

author: Bud
author_rank: Super Contributor
timestamp: July 16, 2018, 11:56:57 am
content: There are 0.1% low thermal PPM SMD resistors, you do not have to use MELF ones .

author: voltsandjolts
author_rank: Unknown
timestamp: July 16, 2018, 04:57:28 pm
content: "MELF Resistors - The World’s Most Reliable and Predictable, High-Performing Film Resistors"QuoteIf MELF does indeed have superior long term stability, maybe that was a deciding factor for them.

author: Bud
author_rank: Super Contributor
timestamp: July 16, 2018, 05:37:10 pm
content: Yes i was also thinking about better aging characteristics as a possible reason

author: precaud
author_rank: Frequent Contributor
timestamp: July 17, 2018, 04:20:17 pm
content: Given the target customer for their gear, Omicron was very brave to give this unit for an Eevblog review!They intimated exactly this in their recent newsletter:"...And this is the moment when you have to take risks. Risks like sending a Bode 100 to Dave at EEVblog."

author: Wolfgang
author_rank: Super Contributor
timestamp: October 06, 2018, 01:46:44 am
content: Quote from: Bud on July 12, 2018, 04:43:53 pmHi,now I have the opportunity to test the B-WIT100 and a functionally equivalent homebrew transformer on a Bode 100 and on the sharpest knife of LF VNAs, a Keysight E5061B-3L5 (35k$, 5Hz to 3GHz). A few € wont do the job, but with about 70€ you can homebrew something decent:https://electronicprojectsforfun.wordpress.com/injection-transformers/at the bottom.

author: Bud
author_rank: Super Contributor
timestamp: October 06, 2018, 09:25:58 pm
content: The VAC T60006-L2030-W514 core appears to be something exotic, $30 Canuck bucks here at Mouser plus shipping, i will probably pass.

author: precaud
author_rank: Frequent Contributor
timestamp: October 06, 2018, 09:37:11 pm
content: I picked up a T60006-L2030-W423 from the Mouse for about 1/3 that much. I want to play around with a 2:1 winding.

author: Wolfgang
author_rank: Super Contributor
timestamp: October 06, 2018, 09:51:51 pm
content: Quote from: Bud on October 06, 2018, 09:25:58 pmQuote from: precaud on October 06, 2018, 09:37:11 pmPlease tell me about the results. My prediction is:Als long the coupling inductance is in the range of 200mH and strays are low (less than 1uH) results will be comparable. A look at Omirons SPICE model gives you some idea:* BWIT 100 WIDEBAND INJECTION TRANSFORMER MODEL* CREATED BY OMICRON Lab ON APRIL 7, 2011* VERSION 1.0** CONNECTIONS: PRIMARY SIDE SIGNAL*| PRIMARY SIDE GROUND* | | ISOLATED OUTPUT 1* | | | ISOLATED OUTPUT 2* | | | |* | | | |.SUBCKT BWIT 1 2 3 4* CAPACITORSCPRI 1 2 14e-12CPRISEC 1 3 85e-12CSEC 3 4 14e-12*RESISTORSRPRI 1 5 0.36RCORE 6 2 35e3RSEC 8 3 0.362* INDUCTANCESLLEAKPRI 5 6 0.85e-6LLEAKSEC 7 8 0.85e-6LMAG 6 2 199e-3* IDEAL 1TO1 TRANSFORMERE 9 4 6 2 1F 6 2 VM 1VM 9 7.ENDS BWITProbably a lot of similar cores with the same material would do.

author: Alextsu
author_rank: Contributor
timestamp: October 15, 2019, 02:53:43 pm
content: Quote from: voltsandjolts on July 14, 2018, 12:58:44 pmCould not compare Analog Discovery (=AD) FRA's performance directly against any of those kilo-$ FRAs like Omicron or Venable. It would be interesting to know if anyone has a chance to test it.But I tried AD to measure Gain-Phase response of a very noisy DIY AC-DC swithcing PSU. The DUT PSU had a high enough conducted EMI level so all my attempts to measure it's frequency responce with USB PC scope-based FRAs failed.Surprisingly, AD was the ONLY device among other low-cost FRAs that gave a well-defined FRA responce of DUT PSU.

author: rbola35618
author_rank: Frequent Contributor
timestamp: October 25, 2019, 02:06:59 pm
content: Can you show us some of your plots. I am interested in seeing your results.Robert Bolanos

author: EEVblog
author_rank: Unknown
timestamp: October 28, 2019, 05:37:21 am
content: Quote from: Wolfgang on October 06, 2018, 01:46:44 amEEVblog APPROVED!

author: Wolfgang
author_rank: Super Contributor
timestamp: October 28, 2019, 05:32:02 pm
content: Dave, you need to look forward to my "Nude Virgin Current Injector" !Stay tunedWolfgang

author: BFX
author_rank: Frequent Contributor
timestamp: November 03, 2019, 06:11:13 pm
content: Not nude but injectorParameters are similar or mostly better like original