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VNA advice wanted
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I've been building up an RF bench (8560A w/ TG, 8648C, 438A, 5386A, Tek 485, LeCroy DDA-125/LC684DLX plus several Chinese DSOs and 3478As and 34401As) with a maximum frequency of about 3 GHz.
I recently noticed that some of the older HP VNA & S parameter sets with a maximum of 3 GHz are not so expensive as to be out of the question. for example the 8753C. With a $2-3K US budget, what models should I be looking at? Which should I avoid? What are reasonable prices for gear in good condition? I'm not an EE, so I've never had the privilege of working in a well equipped lab and the model numbers are quite a puzzle. I'm not aware of a site that lists all the HPAK models of various instruments. by type. I have a VNWA 3E, but have not yet used it, because right after I got it, I bought so much gear that all my time was consumed by reorganizing my workspace. I've collected most of the parts to build an S parameter set for the VNWA, but it doesn't reach the 2.4 GHz WiFi band and I'm contemplating creating a private neighborhood network over about a 40 acre area to allow monitoring PoE security cameras without putting them on the internet. |
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Even though this is an HP group, I think you should consider a different USB VNA. I have a MiniVNA Tiny that goes to 3 GHz. The downside is that it really only has a dynamic range of about 40 dB, but that is enough for 95% of the work I have done with it. The big upside is it runs off a laptop or even off a tablet or phone, so it can easily be used in the field. I have brought it to antennas, test benches and even aircraft to do testing as it is so small and light. My other option was a R&S VNA that worked great, but I couldn't even pick it up! The software for the USB VNAs have lots of features and export capabilities that are hard to find in older VNAs. I use an FFT based SA and a sweeping signal generator for a scalar network analyzer. I can then sweep any part of a filter that has more than 40 dB of rejection. That combined with the VNA pretty much covers everything I need to do. Regards, Mark On Sat, Feb 9, 2019 at 6:02 PM Reginald Beardsley via Groups.Io <pulaskite=[email protected]> wrote: I've been building up an RF bench (8560A w/ TG, 8648C, 438A, 5386A, Tek 485, LeCroy DDA-125/LC684DLX plus several Chinese DSOs and 3478As and 34401As) with a maximum frequency of about 3 GHz.? |
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I see you have a spectrum analyzer with TG. If you get a good quality SWR bridge like Wiltron 60NF50 (or 60N50) or HP 86205A then you are basically set
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to do all kinds of transmission and reflection measurements albeit scalar ones (only magnitude but not phase) That will probably cover a lot of RF work you will be doing. However, if you would like to have a VNA I recommend one that has integrated test set like 8753D (it also comes without test set) It also has a 6GHz option? which would be fantastic. Or 8714ES or 8712ES (make sure it has 50 ohm ports not 75ohm!)? I guess you might be able to find a decent 8753D for about 2K these days if it is fully working. If you want to enjoy the fun of repairing it then of course it comes cheaper. 8714-13-12-11 are of course cheaper and come with CRT not LCD. a decent 8752C with a test set also should not be more than 1.5K-1.8K I guess and it is still great . On Sat, Feb 9, 2019 at 08:02 PM, Reginald Beardsley wrote:
I've been building up an RF bench (8560A w/ TG, 8648C, 438A, 5386A, Tek 485, LeCroy DDA-125/LC684DLX plus several Chinese DSOs and 3478As and 34401As) with a maximum frequency of about 3 GHz. |
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On Sat, Feb 9, 2019 at 05:40 PM, Mark Goldberg wrote:
Even though this is an HP group, I think you should consider a different USB VNA. I have a MiniVNA Tiny that goes to 3 GHz. I'm going to try this system for an educational modular build experience and compact looks practical system: In general:? The schematic:? From this folder:? ? Noted in more detail in regards to the simplified version (and potential frequency range increases with different modules noting specs carefully) from this thread in this group: /g/SoftwareControlledHamRadio/topic/analyzer_comparison/29533629? |
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On Sat, Feb 9, 2019 at 07:02 PM, Reginald Beardsley wrote: "...the model numbers are quite a puzzle..."
To take some of the puzzle out of the model numbers, look at Dr. Kirkby's web pages, for example:? I think the HP/Agilent 8753 series is a great choice that balances capabilities and cost.? I got an absolutely pristine, working perfectly, 8753ES off the auction site a couple years back for about $1800. With the assistance of Dr, Kirkby's friend I was able to add the time domain option which makes it a very powerful addition to my RF bench.? You can download a full set of operation manuals and application notes for the 8753 instruments from Keysight.? Also, there are utilities available from Keysight and from John Miles to do screen captures, save data and so on. |
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Reginald,
I am trying to create some space here and I do have a 8753B with a 85046A test set (50 Ohm, mechanical transfer switch). It's a complete system with interconnect cables, except that test port cables are not included. It's available for well below your 2-3k budget. I also have a 8510B with a 26.5 GHz test set, but it does not come with a source. If interested, contact me off list. Vladan |
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Pete Manfre
Although I very little over your budget I have a beautiful looking and working 8753ES for sale at $3200?+ shipping.? ?Details and photos off list to conserve bandwidth.? Pete wa2odo On Sat, Feb 9, 2019, 8:02 PM Reginald Beardsley via Groups.Io <pulaskite=[email protected] wrote: I've been building up an RF bench (8560A w/ TG, 8648C, 438A, 5386A, Tek 485, LeCroy DDA-125/LC684DLX plus several Chinese DSOs and 3478As and 34401As) with a maximum frequency of about 3 GHz.? |
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How do the 871x series compare to the 8753 series? I read David Kirkby's page on the 8753 series. It seems as if every model offers options to turn it into almost every other model.
Does anyone know of a summary of the 871x similar to Kirkby's summary of the 8753? What I'd like is 30 KHz to 3 GHz with test set. Though what I'd like may not be what I get and I might settle for 300 KHz lower limit and just build a dedicated device for testing EMI filters or buy something like a 3577A. The SMPS noise from my Instek MSO-2204EA is horrible which is not really surprising given it's complete lack of shielding. But that and LED lights have gotten me on an EMI suppression binge. My eyes are a bit glazed over from 15 pages of eBay listings, But an 8753D with opt 06 and integral S parameter switch for around $2k seems reasonable if I'm patient. I'm going to need patience as I really don't have room unless I relocate my bench. |
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Reginald,
If your need for a VNA is driven mostly by EMI filters and measurement, then I'd say you don't need a VNA. A spectrum analyzer (in conjunction with some appropriate probing devices and methods) is most useful for tracking down EMI pathways, and measuring effectiveness of various cleanup techniques. You can't readily design or predict the in-service characteristics of say, a power line filter, with VNA measurements. This kind of filter is not an RF/microwave device with nice, single-ended 50 ohm I/O, and it goes in a non-RF environment. Ed |
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Dr. David Kirkby from Kirkby Microwave Ltd
An Sun, 10 Feb 2019, 02:39 amirb <amir.borji@... wrote: However, if you would like to have a VNA I recommend one that has integrated test set like 8753D (it also comes without test set) It also has a 6GHz option? The external test set does offer some advantages, which is why I bought an 8753ES option 011 (external test test). Testing high power amplifiers is one obvious one. Almost all current high end VNAs have an extra-cost option of a configurable test set.? Dave.? |
¿ªÔÆÌåÓýOn 02/10/2019 07:58 PM, Dr. David
Kirkby from Kirkby Microwave Ltd wrote:
I haven't been following this thread, so I may be off topic, but I wonder if you have read about a couple of VNA "modules" that run off of a USB port on a computer? I don't know what frequency range you need, but I think some of the modules are working up into the low GHz region. They are far cheaper than a full-blown VNA from, say, HP. You should, however, look for a unit that does 4-port measurements: S11, S21, S12, S22, if available, or you'll have to turn the UUT around to get the answers. --doug, WA2SAY, retired RF engineer |
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The EMI filters are just a reason to want 30 KHz rather than 300 KHz. I've been doing a lot of probing with the SA function of the Instek MDO-2000E line. My 8560A just isn't sensitive enough below about 300 KHz which is where the majority of the noise is. Sadly I discovered that GW botched the calculation of the modulus so the series resonant notch of a crystal shows up as a peak.
So how would you evaluate the performance of an EMI filter? It surely looks like a transmission/reflection problem to me. I'm a retired reflection seismologist, so I'm very used to the time domain and impulse responses and to a large degree can look at either a time or a frequency domain plot and cartoon the other domain (thanks to Ronald Bracewell). For that matter, how would you evaluate a crossover network? That's not 50 ohms. I would expect one would need a balun at each end, but I can't see why it matters that it's not an RF line. The conversion between balanced and unbalanced and the impedance matched would be required and the latter probably gets "interesting" if it's a 4 ohm speaker. |
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Actually, I have a VNWA 3E and an xaVNA both of which are 2 port USB devices.
The VNWA has limited dynamic range above 500-600 MHz IIRC and only goes to about 1.3 GHz. The xaVNA covers 140 MHz to 2.5 GHz. I've not actually used either one yet as I have been buying a bunch of test gear and setting up a bench. I've discovered that I don't actually have room in my current space for an 8753, but this is really just intended as a temporary bench. Eventually the bench will probably go in the library (5000+ volumes) which occupies the former 2 car garage. But I've got a dozen or more boxes of technical journals and now superfluous books to clear out. Unfortunately, at 65 there is no work at $50/bbl oil. A friend found a bespoke programming job, but before he could get started the company got bought for pennies on the dollar and upper management were all laid off. So the job disappeared. Playing with electronics by myself in rural Arkansas is not as much fun as working where I had people to interact with who understood what I was doing. So now I interact with strangers in cyberspace :-( I "retired" 11 years ago to look after my parents thinking once I got moved I'd get another contract, but before I could even begin unpacking the crash hit in 2008 and all the contract work dried up. I was having a really tough time emotionally until I discovered the EEVblog forums and the fantastic people who hang out there. But it's still feels rather weird. |
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what do you mean 8560A is not sensitive enough below 300KHz?
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The frequency range is 50Hz to 2.9GHz but you MUST enable DC coupled input (by default it is always AC coupled and freq response is >100KHz) It really meets the specs down to 50Hz. Of course you will need to choose a small RBW and it will be pretty slow but it works. I have a 8560E which goes to 30Hz and I can measure? a 10KHz resonator with it however at 10Hz RBW it is slow. Your VNA will also be very slow for the same reasons your SA is. for low frequency filters such as EMI filters you really only need transmission measurement to see where the resonance is. "Reflection" is not really an issue at frequencies like 30KHz? but still can be measured using a good directional bridge anyway. yes, a balun can take care of the matching but I am not exactly sure if those filters are designed for a specific purely resistive load/source impedance. In RF filters, this is always the case and the impedance is usually 50 (or 75) or rarely things like 100 or 200 or 300 ohms (resistive) so a transformer easily takes care of the matching but i don;t know about EMI filters. For example it might have been designed to have its specified frequency response for a specific inductive or capacitive load. In any case you will need to know that optimum impedance the filter was designed for (if that is indeed how they are designed) However, just to see where the resonance is or to compare two filters, most of the time you dont even need to care about impedance matching. Just the SA with TG is enough The actual insertion loss will be wrong though. Investing on a good EMI probe and even a high frequency active probe (for in-circuit probing) to use with the SA would be my recommendation. On Sun, Feb 10, 2019 at 08:27 PM, Reginald Beardsley wrote:
The EMI filters are just a reason to want 30 KHz rather than 300 KHz. I've been doing a lot of probing with the SA function of the Instek MDO-2000E line. My 8560A just isn't sensitive enough below about 300 KHz which is where the majority of the noise is. Sadly I discovered that GW botched the calculation of the modulus so the series resonant notch of a crystal shows up as a peak. |
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I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A.
I presume I'd need to first measure the input and output impedances and then construct matching baluns.. Whatever is not reflected is transmitted except for any absorption due to resistive losses. So except in certain pathological cases reflection does not matter. But sometimes it does. In reflection seismology the water layer reverberation is a major aggravation. I'm afraid I've gone off the deep end. My power feed for my bench is all shielded with Liquatite SL-516 flex conduit. I cut off the cords, and ran them from Appleton 4SS boxes (which I do *not* recommend as it gets *very* cramped). I bought them because they fit the external space nicely, but got beat up pretty badly getting the wires to fit inside. I still need to mount a 20 A EMI filter where I connect to the mains. I've got a filter, but it's rather large and I still need to find a suitable enclosure. This might seem like overkill, but if you investigate the radiated EMI from a GW Instek GDS-2000E series scope you'll be appalled by the radiated EMI. There is *no* shielding on the SMPS. I plan to correct that as I have a bending brake and can fabricate an enclosure, But after discovering the issue decided that shielding my power feed was worth while. Besides which I really did not have room for runnning all the power cords into power strips. The last attempt at that led to a wad of cables of absurd dimension. As for probes, so far Bob Pease has kept me to the strait and narrow. |
¿ªÔÆÌåÓýFor occasional use, I like the 8753 for its all-in-one-box construction and simple calibration procedure. I find the 8510 more demanding of the operator, excellent though its performance is.The 8753 was made in very large numbers, so the second hand price is relatively cheap. Experience of them at work has been that they have a good reliability record- we¡¯re still using some that are nearly 30 years old and have needed nothing more than routine calibration. Hope this helps. Regards, Alwyn _____________________________________________________ Alwyn Seeds, Director SynOptika Ltd., 114 Beaufort Street, London, SW3 6BU, England. Tel.: +44 (0) 20 7376 4110 SynOptika Ltd., Registered in England and Wales: No. 04606737 Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________
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on my 8560E the AC/DC coupling is under Amplitude softkey menu on the second page. It's probably the same on 8560A
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because on my 8596E it is also under the amplitude menu your analogy with seismology is not quite relevant when we talk about a circuit at 30KHz or few 10's or 100's of KHz The size of the whole circuit and all connections is not even 0.001 of the wavelength contrary to the sizes or distances you are dealing with in seismology For evaluating these kinds of low frequency (lumped) circuits I would get an Agilent oscilloscope with built in function generator which has a bode plot software in it like a DSO1104G which is relatively cheap. You can automatically find the bode plot of? V_out / V_in. I'd think with a little bit of imagination one could also set it up to plot the input impedance as well. Or you can get something like an HP 4192A gain and phase and impedance analyzer and measure the transfer function and input/output impedances down to 5Hz same thing can be done with HP 8508A vector voltmeter. On Mon, Feb 11, 2019 at 01:33 AM, Reginald Beardsley wrote:
I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A. |
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oops, I meant DSO1102G oscilloscope
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by the way, when you put the 8560A in DC coupled mode, be very careful of not applying any DC voltage to the input specially if the attenuation is low. It can easily kill the mixer On Mon, Feb 11, 2019 at 01:33 AM, Reginald Beardsley wrote: I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A. |
¿ªÔÆÌåÓýHi Regi. Measuring the performance of "EMI" filters can be done many ways depending on what kind of data or information is required. There are so many different kinds of filters and so many different applications for them that it is difficult to find just one of two sources of information that will answer all of your questions. Many different filter companies measure things in different ways and few are eager to release their test methodology. I will be happy to help you the best I can off line. Being an old tempest engineer goat my field and EMC has some overlap in different places. As a point of interest have a look at these
papers & sites, if anything it will help introduce you to
many of the terms used and at least provides a primer to the
subject. I will see if I can forward to you additional reading
material in the near future.....has several Dr. appts today and
this week. 73 Gedas, W8BYA Gallery at Light travels faster than sound.... This is why some people appear bright until you hear them speak. On 2/11/2019 1:33 AM, Reginald
Beardsley via Groups.Io wrote:
I've been lazy and not read the entire manual. Where do you set the coupling? I fired it up and tried all the buttons, but did not find the AC/DC coupling on my 8560A. I presume I'd need to first measure the input and output impedances and then construct matching baluns.. Whatever is not reflected is transmitted except for any absorption due to resistive losses. So except in certain pathological cases reflection does not matter. But sometimes it does. In reflection seismology the water layer reverberation is a major aggravation. I'm afraid I've gone off the deep end. My power feed for my bench is all shielded with Liquatite SL-516 flex conduit. I cut off the cords, and ran them from Appleton 4SS boxes (which I do *not* recommend as it gets *very* cramped). I bought them because they fit the external space nicely, but got beat up pretty badly getting the wires to fit inside. I still need to mount a 20 A EMI filter where I connect to the mains. I've got a filter, but it's rather large and I still need to find a suitable enclosure. This might seem like overkill, but if you investigate the radiated EMI from a GW Instek GDS-2000E series scope you'll be appalled by the radiated EMI. There is *no* shielding on the SMPS. I plan to correct that as I have a bending brake and can fabricate an enclosure, But after discovering the issue decided that shielding my power feed was worth while. Besides which I really did not have room for runnning all the power cords into power strips. The last attempt at that led to a wad of cables of absurd dimension. As for probes, so far Bob Pease has kept me to the strait and narrow. |
jafinch78 .
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