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SMA coax cables the kit came with -
Hi all,
Can anyone please help identify the type of coax the original kit SMA cables are using? I like the convenience of how skinny and flexible these cables are. I hate thick, rigid cables, that make everything difficult, add bulk, and move instrumentation from wherever it is to their most convenient bend radius. I'd like to add some more SMA cables to my bench and not sure what to look for. Thank you! Radu. |
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Re: NanoVNA-h4 stuck in DFU mode
that's the problem, i cannot get an image to load onto it. i cant even get the computer to get the correct driver for it.
i have tried two different windows 10 21H2 machines that both show STM32 Bootloader in the device manager under USB Devices but the DFuse.exe tool will not show it as being connected in DFU mode. |
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Re: NanoVNA-h4 stuck in DFU mode
On Mon, Sep 19, 2022 at 07:12 PM, Eric KO4ZEK wrote:
If the device is in dfu mode, install the firmware you want to use. When that's done you turn it off and on and it should work. The device will remain in dfu mode until you upload usable and working firmware to it. -- Gyula HA3HZ ( ) |
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Re: 2 poles filters teminaison impedance
On Mon, Sep 19, 2022 at 11:38 AM, Gerard wrote:
You need to build a proper test jig when you test components. Stray inductance and capacitance will affect your results. For S21 measurements I use a test board like the one below. You can buy NanoVNA test boards (see wiki and other posts for details or build your own from scrap PCB material and SMA connectors. Use the SOL loads by placing them in the fixture as shown. The 50 ohm isolation load is on the right side. When doing the through remove all loads and put a jumper across the device-under-test (DUT) position. After the through calibration and results saved you will see that S21 is 0 dB across the frequency range. S11 will not be of any interest because the series resistors are in place. Remove the jumper and put the MCF in place (remember to ground one lead) Hope this helps you - Roger |
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Re: 2 poles filters teminaison impedance
Hello,
The filter is given as equivalent to a 45M15A. The characteristics give a termination of 4Kohm and 2.5 PF. I also found a more traditional test method to see. On this site, you will see that an another testing with transformers as soon as the impedance of the filter is greater than 1Kohm With the nanovna, I never managed to have a nice curve with my test model. Best with a -8DB dip between the peaks. I played on the values of resistors and capacitors without doing better. I doubt that sentence: Set the trace to display LOGMAG and PHASE of the passing signal (CH1=THRU). LOGMAG = S21 ? also i doudt that sentence: Remove the crystal filter and connect the resistors to get the through characteristics. Next, remove the connection between the resistors, take the isolation characteristics, and CAL DONE in that state so i doudt my calibration. Short an open -->ok load ? only 50ohm, or the two serial resistors, or 50 + serial resistor???? Throught --> only the 2 resistors Isolate --> no thing connected.? I¡¯m not used to using the nano yet, so I doubt May you revalidate and write the correct procedure thank you cdt |
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Re: 2 poles filters teminaison impedance
Another method used by Epson to measure MCF devices is to use matching transformers to perform the 50 ohm to Zt transformation.
This requires considerably more effort than the series method but the advantage is that you retain the S21 measurement range and can measure stop band attenuation to a greater depth. The trick is to get a good matching transformer for the MCF filter frequency. I suggest that binocular core ferrites be used because they require fewer turns and have a high coupling coefficient which means less leakage inductance and a better match. They come in different mixes so you can select the one suitable for the MCF frequency of operation. Roger |
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Re: 2 poles filters teminaison impedance
On Mon, Sep 19, 2022 at 02:28 AM, Gerard wrote:
Yes you have the correct procedure. Below is the test setup used by a Monolithic Crystal Filter (MCF) vendor using series resistors and a shunt capacitor to get the required termination impedance.. Note that if the MCF termination resistance is 520 ohms the series resistor would be 470 ohms (if the test equipment is 50 ohms). When you calibrate with the series resistors connected together the S21 measurement range of the NanoVNA will be reduced. Assuming a 70 dB range for S21 with a NanoVNA and using two 470 ohm resistors in series the S21 range will be reduced by 20 dB so you can only see MCF attenuation to 50 dB. The larger the resistors the worse it gets. With a termination resistance of 2000 ohms the series resistors would add up to 3900 ohms and the S21 measurement range will be reduced by 32 dB. Roger |
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NanoVNA-h4 stuck in DFU mode
My NanoVNA-H4 is stuck in DFU mode. when i try to use the DFuse.exe it does not see the device connected to the computer. when i go into device management i see the STM32 Bootloader listed under USB devices. i have tried several different articles on getting the windows 10 driver installed but nothing seems to work.
thanks in advance Eric W. |
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Re: 2 poles filters teminaison impedance
Hello, Good morning,
Very interesting article. I did a translation in French. Now tell me if I¡¯m wrong about the measurement method. 1) We calibrate the NanoVna and then we measure the filter, we obtain a raw state of the filter (2 peaks). 2) The right measure would therefore be to calibrate the NanoVna with the 2 resistances in series (In our example 940 ohm --> 2*470 ohm) and not 50 ohms 3) Measure next. 4) Observe the curve Similarly, I did not find the NDK 21F15B filter features to check if the manufacturer impedance is around 470 ohm for our example. I understood that in our case, it would take 2 adjustable resistors, and repeat the operation to find the ideal curve. am i right? cdt |
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Re: 2 poles filters teminaison impedance
On Sat, Sep 17, 2022 at 11:27 AM, John Gord wrote:
The latest DisLord firmware for the NanoVNA does allow you to see what theI respectfully disagree with you. The Port Z feature in the latest DiSlord software only does the mathematical calculations necessary to convert the measurements to a different system impedance (like 600 ohms instead of 50) It does NOT change the actual load impedance on the filter itself. The filter characteristics will change if you do not use the actual source and load impedance that the filter was designed for. For example take an IF filter that was designed for a 1000 ohm in/out impedance. If you put 50 ohms on the output the rolloff characteristics will be much worse than at 1000 ohms and no mathematical calculations in the NanoVNA will compensate for that. Roger |
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Re: 2 poles filters teminaison impedance
Hello John,
Thank you for your response 1) First I have to see if I can download it into my nanoVNA (Compatibility) and study how to do it. See picture probably a clone 2) Then I emulate more with a laptop PC, because the view on a 2.8 screen is dificult. I use NanoVNASaver software. I don¡¯t know if another software is needed to have direct access to this PORT-Z device. Finally, I watched two videos on YouTube. One tests quartz (2 legs), the other a house filter made of several quartz. 3)My question is, will it work with a 2-cup (3-legged) filter? cdt |
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Re: NanoVNA App - Installation and Use
#applications
On Sat, Aug 27, 2022 at 10:40 AM, DiSlord wrote:
I think this hardware LCD module problem, my LCD on V2Plus4 also haveThanks for the tip. I got a new display and now the screen capture works. The old display has the version 1.0 and the new display has the version 1.1. |
Eric KO4ZEK
HA3HZ
Roger Need
Gerard
