Copper Mountain VNA for hobby use - Page 1
Forum section: electronics / testgear

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2016, 11:38:34 am
content: I spent much of yesterday looking at the one of the new Copper Mountain 4-port VNAs. Currently I have a VERY old 8754A that I wrote some Labview code to control and get information off it. For my home use, it works well. But the Copper Mountain is about 40 years newer and it's pretty impressive. Looks like they have a 2-port single direction 1.3GHz unit for under 3K.Their 4-porthttp://www.coppermountaintech.com/products/14/808/

author: G0HZU
author_rank: Super Contributor
timestamp: May 06, 2016, 12:36:21 pm
content: I considered these when looking for a decent VNA (for home use) last year. I wanted a 4 port VNA to make it easier to get n port models efficiently from it.On paper these VNAs look really attractive in performance terms and the bonus is the portability and the ability to run with a big hi res monitor. But I think they need to market them better because I can't see us ever buying one of these at work because there isn't enough information on their website to give confidence that these really are contenders against Keysight or R&S. There are a few vague reviews/comments and not much else.Maybe it has changed since last time I looked but the biggest hurdle against these devices is the cost/risk aspect. I strongly suspect that most people at my place of work wouldn't bother to even ask for one of these VNAs to review because there isn't enough marketing blurb to catch their eye and pique their interest..The ideal way into a company like ours is to do a kind of roadshow presentation in a conference room in our building and allow the RF engineers to wander across and watch the demos. In the good old days the reps (eg Keysight, R&S etc etc) were allowed to dish out freebie gifts at these events and this was a surefire way to get every RF engineer to attend. But these days we aren't allowed to accept stuff even if it's just a free mug or pen or cheap/basic RF hand tools.I ended up getting a 4 port Agilent E5071B at auction. I had tried to buy an E5071 as an ex rental but couldn't find one with 1E5, the touch screen and 4 ports. I had been searching for the right VNA for a year or two. I still can't believe I managed to bag the one at the Invidia auction last year

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2016, 10:38:02 pm
content: I was thinking about it for hobby use. Looks like about 10K to replace what I have. If I give up the second coupler, around 7.5K. If I could get that system at 3, I would pull the trigger just because there are so many advantages over my old antique. Maybe one day....The E5071B would be overkill for my home use not to mention way outside my price range.

author: zach.cmt
author_rank: Newbie
timestamp: June 16, 2016, 07:12:31 pm
content: I work at Copper Mountain Tech as an engineer. I can answer questions about our VNAs if you want. I'd also be more than happy to give any software help too.

author: G0HZU
author_rank: Super Contributor
timestamp: June 16, 2016, 11:53:29 pm
content: Hi ZachIt would be nice to see some real world comparison tests against a typical modern VNA from Keysight or R&S. Do you have anything like this? i.e. some critical testing in a typical test fixture.There don't seem to be any credible test reports on your website in this respect. The independent review material I saw on your website was not very convincing and I don't see those vague reviews as adding any technical value. I'd kind of prefer to see some test comparisons made by your own engineering team because you are much more likely to produce credible test data.

author: zach.cmt
author_rank: Newbie
timestamp: June 17, 2016, 08:50:50 pm
content: Did you check out the data sheets?http://www.coppermountaintech.com/download/50/808-1-Data-Sheet/for the 4-port device, andhttp://www.coppermountaintech.com/download/2/TR1300-1-Data-Sheet/for the 2-port, 1-path device.I don't have access to a Keysight VNA, but I can do some testing on our devices. Anything more specific that you'd be interested in that "a typical test fixture?"

author: G0HZU
author_rank: Super Contributor
timestamp: June 17, 2016, 10:23:16 pm
content: I did look at the datasheets and at first it looks impressive. But if I look closer I can see things that will put some advanced users off.For example, the datasheet refers to accuracy rather than uncertainty. Maybe I'm being a bit pedantic here but this means that I don't really know how to interpret the datasheet figures.Do you really mean uncertainty rather than accuracy? I think most engineers would expect to see various graphs that show uncertainty.Other stuff is missing too and one key parameter that would affect my usage is how the uncertainty is affected by the source power level. I try and use a source power that delivers the least uncertainty (in the receiver) for a given task. But your datasheet doesn't help me here. (or if it does, then I've missed it somehow?)Note that I don't claim to be a VNA guru but I am an experienced user and I like to use a VNA to extract n port models of networks for use on a PC. So I like to use a VNA that can deliver model data that is useful on a simulator. Your VNAs look attractive to me because I can get instant access to model data because I would use the VNA on the same PC I run a simulator. Plus I can keep all my save/recall data on my PC as well as all my calibration/fixture data. Also, it's nice to be able to easily view the VNA display on a big hi res monitor.I've worked out how to see a hi res display on a remote monitor with my E5071 but it's quite fiddly to set up. I think your system of 'small/portable' VNA box and the remote PC is the way of the future and big old VNAs like my E5071 take up a lot of bench space.QuoteI could suggest a few basic tests but could you first explain how you measure/prove the figures in your datasheet. How do you prove the measurements? Are they predicted/achieved 'by design' or do you have test setups to verify the performance? I'd be keen to hear how Keysight or R&S do this as well. Obviously, this isn't an easy task.

author: G0HZU
author_rank: Super Contributor
timestamp: June 17, 2016, 11:02:26 pm
content: Note that I've managed to find the source power info (-5dBm ) in the footnotes for the 4 port VNA. Before I found this I assumed it would be at -10dBm and it was missing from the tabulated data.It would be nice to see a graph here but the performance does look to be good here.

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 18, 2016, 02:52:42 pm
content: Quote from: joeqsmith on May 06, 2016, 11:38:34 amanother option, less stellar spec but $500 hobby price friendly... DG8SAQ-VNWA-3http://www.ebay.com.my/itm/DG8SAQ-VNWA-3-Low-Cost-1-3-GHz-Vector-Network-Analyzer-/231954474988?hash=item36019067ec:g:KEMAAOSwJb9WsjIDreviews are available online... unfortunately i'll wait for something around 6GHz at a fortune price to become usefull to me... until then...

author: uncle_bob
author_rank: Unknown
timestamp: June 18, 2016, 03:08:25 pm
content: Quote from: Mechatrommer on June 18, 2016, 02:52:42 pmHiBefore you dive into *any* of these boxes it is very important to consider just what your needs really are. It is trivially easy to run up an enormous tab adding features on a VNA. It is also utterly useless to buy one that does not have the things you are going to use built into it.I can cobble up a couple of mixers and a breadboard style coupler in the basement. With it I can get some information. I can also haul out a 6 GHz HP VNA and take data (with the lights out ... the color CRT really isn't doing very well). The cost of one is vastly different than the cost of the other. The quality of data and ease of use is also more than a bit different as well.It all depends on what you need.Bob

author: RadioDude
author_rank: Newbie
timestamp: June 18, 2016, 04:21:08 pm
content: A good quality VNA up to 4GHz is MegiQ (www.megiq.com) VNA-0440 for about $3000 it is a true 2-port VNA with nice option like match calculator. They seem to be for professional but the price is almost for hobby.I found a review with comparing Rohde & Schwarz ZVL and MegiQ and MiniVNA Tiny athttp://www.gsm-modem.de/M2M/wp-content/uploads/2014/04/IoT-M2M-Cookbook-Harald_excerpt.pdf

author: joeqsmith
author_rank: Super Contributor
timestamp: June 19, 2016, 02:09:39 am
content: I was very impressed with the software.Quote from: zach.cmt on June 16, 2016, 07:12:31 pm

author: G0HZU
author_rank: Super Contributor
timestamp: June 19, 2016, 01:20:24 pm
content: QuotePrices for the E507x range are all over the place at the moment. There are some kite flyers trying for huge money even on a basic 2 port version but if you are patient there are some bargains out there. The cheapest I've seen one is $7k USD but I think the prices are going to fall in the next couple of years. If you are interested in trying out the E507x user interface it is possible to install the VNA SW onto a modern PC and run it in a kind of emulator mode. I disassembled the program code for my E5071 to look at how they manage the SW options etc and I found that there is a hidden simulation mode in their main program code.I assume they used this during the GUI development. This mode allows the GUI programmer to develop and debug a lot of things without needing a real VNA platform on their bench. I've worked out how to launch it on a standalone PC. I can show you how to do this if you want to try it out?I also found in the program code that it supports hi res graphics and I found out that the real E5071B VNA can do this too (with a suitable external monitor and some setup changes in the VNA) and I can now access this hi res mode on my E5071B here at home and escape from the native VGA graphics. Depending on what graphics adaptor and external monitor you use you can get some really nice displays with the E5071. If you just read the manual the external monitor is locked to VGA mode on the E5071B even with a hi res monitor but you can make changes to divert the graphics adaptor to the external monitor only and then invoke the high res modes.See the screenshot below for the simulator mode running in hi res mode. This was taken on this PC and I think my monitor is 1920x1200. The simulator mode is fully interactive and you can export simulated s parameter files and play with the time domain modes as well. However, I don't think you can save/recall states to the regular slots as it appears to have failed in the image below. But you 'can' save and recall states to a text file on the PC hard disk with the simulator using the File Dialog soft button in the screenshot below.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 19, 2016, 05:00:35 pm
content: Thanks for the offer. It may be worth the time to document it as others may be interested in this as a heads up on how it drives for when the prices get into the hobby range. $7K is more than I would spend on one. I just don't use my antique one enough and it's for hobby work only.Quote from: G0HZU on June 19, 2016, 01:20:24 pm

author: chscholz
author_rank: Regular Contributor
timestamp: September 16, 2016, 04:22:44 pm
content: Quote from: G0HZU on June 17, 2016, 10:23:16 pmIt depends on what data you are looking at.Specificationsare the only data that are guaranteed. If you send VNA to our R&D service center in Columbia, MD your'll get an instrument back that meets each and every spec in the data sheet. The equipment we use to verify the specifications is traceable to national standards ("NIST traceable"). We have meteorologists on staff who make sure that everything stays within specified limits, measurement uncertainties are met, etc. The fancy term for that is guardbanding. We work closely with various national standards labs, facilities are ISO, etc. certified and get audited (internally and externally) on a regular basis.Typical dataare performance data that a majority of the VNAs meets when they leave the factory, but they are not guaranteed. During calibration we track these data, analyze them, perform statistical analysis on them. As a rule of thumb, about 70% of all manufactured instruments meet typical data.Some vendors give additional performance data in their data sheets, they are not always very meaningful. Popular items are:SPD (supplementary performance data).These performance data are not measured or tracked during calibration.Characteristic performance.I can't tell you what that means. It's "non-warranted performance that most units exhibit". Since some types of instruments give only "characteristic performance" data, I speculate that the vendor who quotes these data keeps statistics. It's not typical data, it's not SPD either, probably somewhere in between.Sometimes you see atrace in a data sheet. Those are measurements that are taken form a single instrument, worth less than SPD data.I have seen one performance measure that was labeledexpected performance calculated based on [previous model].When comparing spec sheets, make sure you compare apples to apples (same output power, same IF bandwidth, etc.). Vendors can choose measurement conditions as they please. However for VNAs there are a few de-facto standards to specify dynamic range, noise floor, output power, etc. But I've seen one data sheet where dynamic range was specified with smoothing on. This of course makes this specific VNA look quite a bit better than it really is.Also, be cognizant of footnotes. I've seen specifications of e.g. dynamic range between say 100 kHz and 1 GHz, with a footnote stating that the specification does not apply between e.g. 200 kHz and 300 kHz. What kind of spec is that?My experience with VNA customers is that 1) they are very sophisticated and knowledgeable 2) they get fairly upset when they discover how much marketing spin makes it into many data sheets.Does it matter for hobbyists?It all boils down to the question if you need accurate, precise, repeatable and reproducible measurements. I would argue that if you can't tell how good your measurement is, why would you measure at all?

author: G0HZU
author_rank: Super Contributor
timestamp: September 26, 2016, 10:39:48 pm
content: Thanks for the reply. I'm guessing that you are connected with R&S because they are based in Columbia MDYes, it is always risky to compare specs in datasheets. Lots of traps for the unwary. I was hoping that Copper Mountain (and maybe even Keysight) would give a reply. It would be great to see or read about how the testing is done.I'm nervous of the specs in the Copper Mountain datasheets because they refer to accuracy rather than measurement uncertainty. So this confuses me because I don't know if they are giving qualitative or quantitative figures. So it's hard to compare specs with Agilent etc.

author: G0HZU
author_rank: Super Contributor
timestamp: September 26, 2016, 11:37:17 pm
content: If anyone wants to play with the (PC simulated) UI for the Agilent E5071C I've put some basic instructions below that you can try.The idea is to install the VNA application on an old XP PC and then run it withE5070 /sas in E5070.exe /sThis command launches the app in an interactive simulator mode on a PC.Note that the app tries to install to a different drive than the main C:\ drive so it will fail here. So the instructions below are a crude workaround to install it as a network image onto the c:\ drive in program files. Someone with better IT skills than me might be able to suggest a cleaner/easier way to get it to install on a regular PC.If you are successful you will be able to lauch the VNA app and play with a built in simulation of a 4 port device.IMPORTANT: the installer will try and launch this app from startup every time you start the PC so best to remove the launcher shortcut from the startup menu in windows.Otherwise you may get a bit fed up seeing it try to launch without the /s command and it will crash out saying it has a fatal error in that it can't find the VNA hardware.You really do need to launch it as E5070 /s to get it into simulator modeQuote