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Re: Transistor S parameter measurements
You might search in some of the VNA-associated notes from HP and Motorola.
I no longer have specific references, but I remember specifically, both suppliers addressed the problem with fixture designs. HP (Keysite) still sells fixtures for the purpose applied to test equipment specific applications. Cloning those fixtures might be the best approach. When Motorola came out with their line of bipolar (BJT) RF power transistors, they documented the test fixtures. A few other Japanese suppliers of small-signal devices did the same. Wish my memory of 40 to 50 years ago was better. Dave - W?LEV On Tue, Sep 22, 2020 at 8:23 PM Reginald Beardsley via groups.io <pulaskite= [email protected]> wrote: I found some discussion over a year ago, but nothing since. Has anyone-- *Dave - W?LEV* *Just Let Darwin Work* |
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Transistor S parameter measurements
I found some discussion over a year ago, but nothing since. Has anyone done this?
I had trouble finding any information on fixture design. Ultimately I settled on biasing the candidate transistor with PCB edge SMA-F connectors on a board and then with the appropriate appendages measuring it with the nanoVNA and possibly some other VNAs. I just made up a bunch of bare fixture boards. First up is a 2N3904 in CE form and no feedback. After that I thought I'd try CB and CC before moving on to feedback. I know I'm not the only one interested, but I can't seem to find much record of prior work. Have Fun! Reg |
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Re: MMCX amd MCX calibration standards
#adapters
I am surprised they were not good beyond 1ghz. The smaller geometry, if constructed with care should have made it as easy or easier than making an sma calibration standard. I wonder if a single 50ohm resistor might give better results, or using two physically smaller 100ohm than the 0605 size ( not that I would be able to physically do it).
Steve L |
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Re: MMCX amd MCX calibration standards
#adapters
Some time ago i made a calibration kit using mmcx connectors. I ued 6 female mmcx connectors like these .
One is left as is -> open. Second is shorted by a strip of copper foil -> short. 3 and 4 : two 100 Ohm 0.1 % 0603 resistors are connected between the middle and the outer pins -> two 50 Ohm loads. Two connectors are soldered back - to - back -> through. For the connection of the mmcx cables (male to male) i used mmcx to sma adapters. The calibration kit was good to 1 GHz. Bert |
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Re: TDR setup for NanoVNA #tdr, add electrical delay
Jim wrote:
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# The longest cable is more a function of the step size than the highest frequency. It has to do with ambiguity. Understood. All three of those formulas assume we only have the 101 datapoints of a standalone nanovna. As I stated: # Though of course, far better to figure out how to process more data points. # Perhaps with nanovna-saver, or a nanovna-SAA2 Jerry, KE7ER On Tue, Sep 22, 2020 at 08:29 AM, Jim Lux wrote:
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Re: TDR setup for NanoVNA #tdr, add electrical delay
On 9/22/20 8:00 AM, Jerry Gaffke via groups.io wrote:
John wrote: The longest cable is more a function of the step size than the highest frequency. It has to do with ambiguity. |
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Re: A practical example of evaluating unknown cables using the TDR feature of a nanoVNA
#training
#applications
#tdr-step-response
It would be good for this to be posted to the wiki and/or in a file download location. The questions about how to do TDR measurements one up frequently, and last week we had a very rude and frustrated poster throw their hands up and give up (although that person could have benefitted greatly from reading what documentation does exist, but that is another story).
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Re: TDR setup for NanoVNA #tdr, add electrical delay
Thank you, John. The founding concepts you described I was already aware of, but I'm sure they were beneficial to anyone following the post. I was specifically interested in the reasons for the settings you chose (Such as REAL format and TRANSFORM), as I am not yet familiar with all the features of the VNA. Understanding the f-to-T function makes it clearer.
My adjustment of the STOP frequency allows an overall view (albeit at low resolution) of the entire length of cable which hopefully will catch some indication of any discontinuities along the line. If desired, using a higher STOP frequency along with the ELECTRICAL DELAY can then provide a more detailed indication of the nature of the discontinuity. Thanks again! |
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Re: TDR setup for NanoVNA #tdr, add electrical delay
John wrote:
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# I noticed an interesting effect: If you set the Start frequency at half of the step size # (say 15MHz to 3000MHz, 101 points), the impedance steps at the first (and every odd) # "delay overflow" are inverted!! Probably makes perfect sense to someone (but not to me). That's very curious indeed! Perhaps with some head scratching, one might use this effect to distinguish between ambiguous regions on long runs of cables. Though of course, far better to figure out how to process more data points. Perhaps with nanovna-saver, or a nanovna-SAA2 At the top of Bryan's document, Step 2 states: "I changed the nanoVNA stop frequency to 130 MHz which gives a maximum length that can be observed in the nanoVNA of about 31.5 m. " Speed down the cable is 3e8*0.66 meters/second, assuming a velocity factor in his cable of 0.66. So Bryan's 31.5m might represent a delay of 31.5/(3e8*0.66) = 160 ns. If we assume Bryan did not take the velocity factor into account, that's 31.5/3e8 = 105 ns. Neil's formula gives a delay of tmax = 39/fmax = 39/130e6 = 300 ns John's formula gives us a delay of tmax = 100/fmax = 100/130e6 = 769 ns I prefer the looks of John's formula, the others appear to have been arrived at empirically. But that's a rather large spread. Jerry, KE7ER On Mon, Sep 21, 2020 at 10:33 PM, John Gord wrote:
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Re: MMCX amd MCX calibration standards
#adapters
Are those the minute connectors used on the teaching board, and, I think on drone circuitry? I thought the drones used 5ghz, an area a bit tricky for home-made standards and somewhat out of the nano range.
I presume you have the sma to MCX converters..... I have seen them on Fleabay. You will need a number of mcx connectors, some tiny surface mount resistors (probably safer with one 50ohm for load rather than trying to solder two 100ohm in parallel which would give better top-end performance). The open is easy - do nothing, the short is a big blob of solder where you would attach the coax. Study some utube and internet searches on making sma standards first, so you know what you are letting yourself in for. Maybe make some sma standards for practice and see how they perform against the standards with the vna. Experiment and see what happens. I am sure others would be interested in your results. That is how most of us learn. Steve L. G7PSZ |
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Re: A Good source for Calibrated Loads in formats other than SMA -
#calibration
On Tue, 18 Feb 2020 at 17:23, Bill Smotrilla <smopho@...> wrote:
Array Solutions sells precision calibration loads in formats other than I think "precision" is a bit of an exaggeration there. Several are transitioning from N to SMA, which have very different diameters, so significant shunt capacitance, as a change in transmission line diameters is equivalent to a shunt capacitance, as any decent book on transmission lines will show. Dave |
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nanovna saver do not communicate with windows 7?
#nanovna-saver
Jean Mario Charest
Hello, I installed nanovna saver on my labtop. My labtop use windows 7 but I installed all drivers for USB connection but the nanovna connect with this port 3 but it don't communicate with nanovna saver? So it communicate with my android phone! I have the same problem with my UBUNTU 18.04.5. The port connect but not communicate!?
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Re: A Good source for Calibrated Loads in formats other than SMA -
#calibration
Hi Kurt,
DO you have a view on cal kits for MMCX connectors, or is it ok to cal up to an sma (female) then have a cable SMA male to MMCX socket (female polarity) Thanks Nick |
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MMCX amd MCX calibration standards
#adapters
Hi All,
Does anyone have experience building the calibration standards for MMCX and MCX antenna connector - sockets? Thanks Nick |
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Re: A practical example of evaluating unknown cables using the TDR feature of a nanoVNA
#training
#applications
#tdr-step-response
Thank you Bryan for your excellent and very explicit document.
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Jean F5EDP -----Message d'origine-----
De : [email protected] <[email protected]> De la part de Bryan, WA5VAH via groups.io Envoy¨¦ : mardi 22 septembre 2020 04:49 ? : [email protected] Objet : [nanovna-users] A practical example of evaluating unknown cables using the TDR feature of a nanoVNA #applications #tdr-step-response #training nanovna users: Sometimes we are handed equipment that we want to use; however, we are not given any information about that equipment. I experienced one such issue recently when I purchased a house with coaxial cables inserted into the walls long before I arrived. The cables had been installed when the house was built (18 years earlier) and I did not want to tear into the walls of the house in order to learn about the cables. I wanted to re-use these cables to send electrical data from an infrared sensor near my TV to my stereo system which was located across the room. The attached document shows how to use a nanoVNA and Time-Domain Reflectometry (TDR) to determine the impedance, consistency, and electrical length of the unknown cables. I didn't have to tear up my house and my infrared repeater system for remote controlling my stereo works just fine using the cable I characterized. I consider this a success story. I hope folks find this use of a nanoVNA interesting and encourages them to use the TDR feature of a nanoVNA for a variety of purposes. It is a really useful capability where coaxial cables are involved. -- Bryan, WA5VAH |
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Re: TDR setup for NanoVNA #tdr, add electrical delay
Jerry,
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I noticed an interesting effect: If you set the Start frequency at half of the step size (say 15MHz to 3000MHz, 101 points), the impedance steps at the first (and every odd) "delay overflow" are inverted!! Probably makes perfect sense to someone (but not to me). --John Gord On Mon, Sep 21, 2020 at 09:39 PM, John Gord wrote:
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Re: TDR setup for NanoVNA #tdr, add electrical delay
Jerry,
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I think the discrepancy in maximum delay range is confusion between the range shown on one screen and the range available when including Electrical Delay. As you surmised, with 3GHz and 101 points, a discontinuity with a delay of 1.5ns also shows up at (1.5ns +33.3ns) and (1.5ns + 66.6ns), etc. --John Gord On Mon, Sep 21, 2020 at 08:20 PM, Jerry Gaffke wrote:
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Dr. David Kirkby, Kirkby Microwave Ltd
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