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Hi Hello, has anyone used this firmware for 75ohm, it is on a Russian forum http://www.cqham.ru NanoVNA forum I need an instrument only for measuring small lengths of rg6 cable, up to 20m, open, damaged and short Thanks
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You don't need special firmware to do that with the H4 - any of the recent versions of DiSlord's firmware will make those measurements.
Calibrate as normal with a 50-ohm load.
Then in Display -> Port-Z menu, enter 75 ohms. This causes the firmware to use 75 ohms for the Z0 in calculations.
And you can use the Measure -> Cable menu to turn on some measurements on the left of the screen, which will include the Z0 of the cable, the cable's loss, and an estimate of the length (based on your entry of velocity factor). To use this measure function, just set the start frequency to a low value, the stop frequency to a value that will cause at least one half-circle to be drawn on the smith chart, and leave the other end of the cable you are testing either open or shorted. In fact, this method will work without setting the 75ohm Port-Z. You only need that if you are trying to calculate impedances for matching, etc. Try it - it's the tool I use for evaluating cables, and works quite nicely. If it can't display the cable impedance, it means something is wrong with the cable or connectors.
You can alternately use the Display -> Transform menu to emulate a TDR measurement, which may help find the distance along the cable to a damaged spot - you will want to read up on how to do that, it is a bit more involved to set up and execute correctly.
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But I don't have the option Display -> Port-Z menu, enter 75 ohms
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Which firmware version do you have? You can see at config -> version, or on older firmware at the startup screen. And I presume that you have a nanoVNA-H4 model, based on the title of your message. You can get the latest released firmware from DiSlord at this link: https://github.com/DiSlord/NanoVNA-D/releasesBe sure and choose the file with -H4 in the name. But you don't really need it - the measure cable function will show you the impedance of the cable (75 ohms). It looks like you have enabled Measure -> Cable, but only see the loss value. It only shows the values it can compute, so you need to attach an open-ended cable to the S11 port, and set the frequency span as I noted in my last post: the upper frequency needs to be at least what will make the cable be 1/4 wavelength (i.e. 1/2 circle or more on the smith chart trace). I normally calibrate from 1MHz to 30MHz, and that covers cable lengths from about 40meters to 2.5meters. Higher upper frequency needed for shorter cables. And on the H4, you should set your "Stimulus -> Sweep Points" to 401, which gives you better accuracy with still a fast sweep time. Stan KC7XE
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Hey Stan, I'm interested in this function as well. I have an Aursinc H4 with firmware 1.2.40 and have not been able to locate the a Port-Z menu either. Thanks Stan!
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I too have a recently purchased H4 and the firmware is 1.2.14 and I do not have that option nor is it listed on my printed menu map. What version do you have?
Dan KE6PO
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OK, something weird is going on here.
The attached screenshot is from my nanoVNA-H4.
The port-z is the last item on the display menu. It has been in the DiSlord firmware for many versions, perhaps for a year now . I don't remember which version it was added.
I run version 1.2.40 (the latest), but I just re-installed version 1.2.20, and it has the same port-z menu item (in fact this screenshot is from the 1.2.20 version).
So it should definitely be in your 1.2.27 version - I'm not sure about the 1.2.14.
Since it is not appearing on your menu, something may be wrong with your config, or somehow you have firmware from a strange branch that didn't include this feature. I would start by doing a "config -> expert settings -> more -> clear config", and restarting your H4. This loads factory defaults into many of the internal settings, and is sometimes necessary to clear left-over bits from earlier software versions. Hopefully it will cause the menu to appear.... If not, maybe update your firmware to the latest (at the link I posted before) and hopefully that will fix things.
p.s. I usually don't encourage people to update firmware unless they are missing a feature that they need, since the firmware has been very good since v1.2.00 (and even before then). That's why I recommend instead doing a clear-config first to see if that works.
I hope this helps --
Stan KC7XE
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Yes, very confusing indeed. I have the verified Dislord1.2.40 firmware installed on multiple NanoVNAs and none have Port-Z. In addition, I can find no structure map that includes it. Would it be possible to direct me to the current DFU file that your are sure contains this menu item. I teach a NanoVNA class at our local Ham Shack and would love to demonstrate this feature. Thank you Stan! -Rusty
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Ok, just to be sure (again), I just now re-downloaded NanoVNA-H4.v1.2.40.bin from DiSlords github page at https://github.com/DiSlord/NanoVNA-D/releases and installed it using STM32CubeProgrammer. This is the same thing I did last night with NanoVNA-H4.v1.2.20.bin Both versions from these files show the PORT-Z item as next-to-last in the Display menu, per the attached. I just searched for PORT-Z on the DiSlord release page linked above, and it shows that this function was added to the firmware in v1.1.00 way back in Dec 2021. I have seen it ever since. Here is DiSlord's release note on this function: "Added module for normalization of impedance (DISPLAY-> PORT Z 50 -> XX), allows you to see what the DUT would be if the device had the same impedance as it. Works for two ports, which means filters can be measured as well. This will allow you to measure 75 ohm systems, or even higher-impedance filters (there are limitations, the higher the impedance, the lower the dynamic range). Calibrate as usual to 50 ohms, no matching adapters are needed." Also, search these message archives for PORT-Z entries back in that timeframe - there were several threads of discussion on it. SO: there is something in your config or hardware that is not allowing this menu to show. Did you do a clearconfig? (clearconfig 1234 from the terminal, or from the menu)? My hardware is a relatively old H4, hardware ver 4.3 I think. But I don't think any of the new hardware changes, which are mostly just the replacements for the Si5351 chip (MS5351, etc), would have changed anything to do with this software function. Sorry if I sound a little off, but I am very surprised you are not seeing this function - it really has been there for years. And I'm surprised that there is more than one of you with the same issue. Maybe someone else on this list can shed some light on what could cause this.
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Thank you Stan! I understand the frustration, but will try to see if I can help to resolve the issue on my end. Yep, that's the same firmware that I have, but will try the DFU again. Thank you for all that you do! -Rusty
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Stan, I want to thank you for your effort with this. I did get it working. I was running Dislord firmware version 1.2.27. For whatever reason, this version didn't have PORT-Z, although it should have if the update was made in version 1.1.00. V1.2.40 took care of the issue. I am excited to have this function. Again, Thanks!
-Rusty (Litchfield Pk. AZ)
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Hi Stand
Thank you for all this precious infos about Dislord firmware functions,
Did H4 firmware has an already function to mesure the Z0 (specific impedance of a coax cable) as 50.5 Ohm or 76 ohm directly ? If there any youtube video schowing this function ?
73s Nizar
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On Tue, Nov 26, 2024 at 12:25 PM, Team-SIM SIM-Mode wrote:
Did H4 firmware has an already function to mesure the Z0 (specific impedance
of a coax cable)
Yes, as I noted before, it is done by enabling the "Measure -> Cable(s11)" menu item. I am not aware of a video about this, but it is very easy to use. Just calibrate OSL as normal, using the standard 50ohm calibration - I chose for this example calibrating from 1MHz-30MHz, and calibrated at the end of the short pigtail cable, where I will attach the cables to be measured. As I mentioned in a prior post, the top frequency needs to be high enough so that the smith chart draws at least one half-circle with the length of cable you are using. 30MHz will work for cables over about 2M long. See attached two images. For the first, I attached a 3-meter length of RG223/U, and you can see on the left side the cable measure data shows it at 48.7 ohms impedance, with a loss of 300mdB (0.3dB) at 30MHz. I can move the cursor to see the lower loss at lower frequencies. In the second image, I attached a 3-meter length of Comcast CATVX cable (which they provided for their Gigabit router service). It shows 74.6 ohms impedance, and a loss of 233mdB (0.233dB) at 30MHz. Very easy, very quick. The far end of the cable was just left open. Now, exactly how accurate is the impedance measurement? I don't know, but it is within at least a few percent, and I know if I have 75 ohm coax or 50 ohm, or 92 ohm or whatever. And if the cable is bad, the impedance is usually way off, or doesn't get shown at all - I have a 100' length of RG8/U which won't report an impedance since it had some water penetration. There are lots of other methods to characterize cables with the nanovna, but this one is very easy to use and has good accuracy. If I am making tuning stubs or something critical, I use other methods. But for quick cable characterization for loss estimates, impedance, and length, this works very well. Note that the length estimate is only as good as the velocity factor you enter. Or you can enter a measured length, and it will calculate the velocity factor. And of course, the velocity factor and impedance of all coax cable types varies somewhat due to manufacturing tolerances and materials, so it is never an exact value. I hope this helps, Stan KC7XE
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Hi Stan
Thank you very much for this appreciated engneering analysis of Dislord new function measuring coax cable impedances and loss's , wonderfull function , Thanks to Dislord also .
73's Nizar
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You're welcome - enjoy using it.
But it is not new, it was added to the nanoVNA in Dec 2021.
Stan
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On Tuesday 26 November 2024 09:22:01 pm Stan Dye via groups.io wrote: On Tue, Nov 26, 2024 at 12:25 PM, Team-SIM SIM-Mode wrote:
Did H4 firmware has an already function to mesure the Z0 (specific impedance
of a coax cable)
Yes, as I noted before, it is done by enabling the "Measure -> Cable(s11)" menu item. I am not aware of a video about this, but it is very easy to use. Just calibrate OSL as normal, using the standard 50ohm calibration - I chose for this example calibrating from 1MHz-30MHz, and calibrated at the end of the short pigtail cable, where I will attach the cables to be measured. As I mentioned in a prior post, the top frequency needs to be high enough so that the smith chart draws at least one half-circle with the length of cable you are using. 30MHz will work for cables over about 2M long.
See attached two images. For the first, I attached a 3-meter length of RG223/U, and you can see on the left side the cable measure data shows it at 48.7 ohms impedance, with a loss of 300mdB (0.3dB) at 30MHz. I can move the cursor to see the lower loss at lower frequencies. In the second image, I attached a 3-meter length of Comcast CATVX cable (which they provided for their Gigabit router service). It shows 74.6 ohms impedance, and a loss of 233mdB (0.233dB) at 30MHz. Very easy, very quick. The far end of the cable was just left open.
Now, exactly how accurate is the impedance measurement? I don't know, but it is within at least a few percent, and I know if I have 75 ohm coax or 50 ohm, or 92 ohm or whatever. And if the cable is bad, the impedance is usually way off, or doesn't get shown at all - I have a 100' length of RG8/U which won't report an impedance since it had some water penetration.
There are lots of other methods to characterize cables with the nanovna, but this one is very easy to use and has good accuracy. If I am making tuning stubs or something critical, I use other methods. But for quick cable characterization for loss estimates, impedance, and length, this works very well. Note that the length estimate is only as good as the velocity factor you enter. Or you can enter a measured length, and it will calculate the velocity factor. And of course, the velocity factor and impedance of all coax cable types varies somewhat due to manufacturing tolerances and materials, so it is never an exact value.
I hope this helps,
Stan KC7XE Neat! II may have to play with this a bit. I've been wondering about things like the pairs in CAT5 cable, ferinstance... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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