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Re: Help with LPF Measurement
yay indeed.. Pretty cool.
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-----Original Message-----
From: <[email protected]> Sent: Mar 13, 2025 11:31 AM To: <[email protected]> Subject: Re: [nanovna-users] Help with LPF Measurement Jim, Dave, et al., Thank you very much for your suggestions. I rebuilt the filter using discarded SMA connectors I found in my junk box along with actual 270 pF caps that I ordered overnight from AMZN. It's all on the same board I've reused several times, so please excuse the abrasions, drill attempts, etc. The results are just as you predicted. Images attached. Again, thank you very much for your help. Yay!! Mitch NK3H |
Re: Help with LPF Measurement
THAT looks much better built .. and shows the predicted results ... GOTCHA :-)
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looks neat .. and works like it should so you see its very often not just the components you use but how you arrange them and as higher you go in frequency as more you have to take care of such things (no way to build such an ugly manhatten style construction for uhf or shf and show predicted results) i guess main thing is the connectors .. and solder the caps direct to ground (with short leads) finetuning could be done with the caps and with the coils (if you can move the windings a? bit on the core) anyway .. you for sure learned something (and others on the group see what to do and what NOT to do if building a filter) ... or in fact we all learned from it :-) happy homebrewing ... 73 dg9bfc sigi Am 13.03.2025 um 19:31 schrieb Mitch NK3H: Jim, Dave, et al., |
Re: Help with LPF Measurement
Jim, Dave, et al.,
Thank you very much for your suggestions. I rebuilt the filter using discarded SMA connectors I found in my junk box along with actual 270 pF caps that I ordered overnight from AMZN. It's all on the same board I've reused several times, so please excuse the abrasions, drill attempts, etc. The results are just as you predicted. Images attached. Again, thank you very much for your help. Yay!! Mitch NK3H |
Re: Help with LPF Measurement
This - get some 4 leg SMA jacks and solder two of the legs to the copper clad at the edge of the board. Cut the upper two legs off. That will give you a nice transition.
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Depending on where you are, you can probably get jacks mail order in a day. 10 of them for $8 -----Original Message-----
From: <[email protected]> Sent: Mar 12, 2025 11:54 PM To: <[email protected]> Subject: Re: [nanovna-users] Help with LPF Measurement Mitch, Try making the ground connection to your filter very short, say 5mm or so. Also, try multiple ground wires. The currents to ground from all the capacitors in the filter flow through that ground connection, and if it has much inductance it will have a voltage drop that limits the rejection of the filter. If you have the connectors available, a better connection method is to solder an SMA connector shell directly to your ground plane at the input and another directly to the ground plane at the filter output. Then connect the center pins of the connectors to the input and output and connect your cables. If you just have some SMA pigtails (or can make a couple by cutting an SMA cable in half), you can connect the shield of a pigtail to your ground and the center wire to your input and similarly connect an output pigtail. Then connect those pigtail connectors to the NanoVNA. As others have mentioned, making all the component leads as short as you can will help, but the grounding is probably the bigger factor at this point. --John Gord |
Readings are not correct for NanoVNA F V2.
Does anyone have a web-site or youtube that goes through the set-up on using the F V2 for checking Coax lengths. The new one I have does not show the correct length, example a known 15.24m / 50ft coax comes up over 3 times that. Thinking maybe velocity-factor inputs. No help. The H4 VNA I have is spot on with the numbers. Any help would be grateful. Thanks
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Re: Help with LPF Measurement
How do you know it's filtering the harmonics out? Feeding in a square wave (into a non-resistive load) might not have the harmonic structure you expect.
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It's really hard to interpret the wiggles after the transition in any meaningful manner, short of dumping them into some software and running an FFT. And with a sine excitation, you need to pick a couple frequencies to test at - say 30 and 50 MHz. I'd believe the VNA. As an experiment you could download ELSIE and build the circuit with the inductance from the leads and see what it gives you. If you want something simpler, just use the first pi section - shunt C, series L, shunt C. -----Original Message-----
From: <[email protected]> Sent: Mar 12, 2025 9:48 PM To: <[email protected]> Subject: Re: [nanovna-users] Help with LPF Measurement Hi Jim, Thank you for your suggestions. I will shorten leads and properly dress the components tomorrow. BTW I had no 270 caps but had 50s and 220s, hence the two caps in parallel. You make a really good point in saying "the filter's not working right...." But what I don't understand is why the results from the sig generator/oscilloscope show the filter is filtering out high frequency harmonics pretty well, but the NanoVNA shows a very weird S21 result. It improved slightly when I added the ground leads between the board and the test rig (my bad for missing that!!), but it's not even close to what it should look like. Onwards....Thanks again. Best, Mitch NK3H |
Re: S-Parameter Plotter
On Mon, Mar 3, 2025 at 07:44 AM, Larry Macionski wrote:
Larry, I still use Brian's excellent antenna simulation programs today. In fact, just about every week. (Different story not for here.) But, I run them on both a very new macOS computer and a Windows 10 computer using this app: It works very well. There's a couple features with YO that I haven't gotten working right because of the various calls into and out of a controlling batch file, but overall it's a great experience, still. The best part is that simulations run very quickly - minutes at most instead of overnight. 73, Clarke K1JX |
.NanoVNA-H v3.5_L: white screen - how do I connect USB to fix?
I couldn't connect to the unit and somehow managed to wipe the processor.
I've tried resetting it to reconnect, but the only response I get is in STM32Cube Programmer 'UR is set by HWrst' or something similar. I tried shorting BOOT0 to VDD as noted, screen remains white, no connection. Any suggestions would be appreciated! |
Re: Help with LPF Measurement
Things are beginning to look a bit more like a LPF with the "ground"
connected! Other suggestions have been made which are right on. Keep us posted on your progress. Dave - W?LEV <> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Thu, Mar 13, 2025 at 4:27?AM Mitch NK3H via groups.io <mitch= [email protected]> wrote: Dave,-- *Dave - W?LEV* -- Dave - W?LEV |
Re: Help with LPF Measurement
You may be looking for the graphical version of the map, but I threw this into the AI Grok app on my iPhone and it listed them all out.
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“ Menu Structure Map for the NanoVNA F V2.” You may or may not know, but these AI apps are amazing and scary all wrapped together but I don’t use search engines any longer, too much hunting and pecking to find the answer where the AI app responds with all the information already consolidated. If you haven’t, I would recommend at least trying it out .. Tom 73 "Reality is the moment in which we live, all else is just a memory... "Make the MOST of Reality” ? KTCNC ? ??????? "Kick the Dust Up" On Mar 13, 2025, at 08:59, CLIFTON HEAD via groups.io <aecret@...> wrote: |
Re: Help with LPF Measurement
There are a bunch of them online. Have you tried Googling?
Compare the menu that you think is right to your NanoVNA because there are several variations. On Thu, Mar 13, 2025 at 8:59?AM CLIFTON HEAD via groups.io <aecret= [email protected]> wrote: Off subject, does anyone know where to get a Menu Structure Map for the |
Re: Help with LPF Measurement
Off subject, does anyone know where to get a Menu Structure Map for the NanoVNA F V2. My new one did not come with one. Thanks
________________________________ From: [email protected] <[email protected]> on behalf of John Gord via groups.io <johngord@...> Sent: Thursday, March 13, 2025 1:54 AM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] Help with LPF Measurement Mitch, Try making the ground connection to your filter very short, say 5mm or so. Also, try multiple ground wires. The currents to ground from all the capacitors in the filter flow through that ground connection, and if it has much inductance it will have a voltage drop that limits the rejection of the filter. If you have the connectors available, a better connection method is to solder an SMA connector shell directly to your ground plane at the input and another directly to the ground plane at the filter output. Then connect the center pins of the connectors to the input and output and connect your cables. If you just have some SMA pigtails (or can make a couple by cutting an SMA cable in half), you can connect the shield of a pigtail to your ground and the center wire to your input and similarly connect an output pigtail. Then connect those pigtail connectors to the NanoVNA. As others have mentioned, making all the component leads as short as you can will help, but the grounding is probably the bigger factor at this point. --John Gord |
Re: Help with LPF Measurement
Mitch,
Try making the ground connection to your filter very short, say 5mm or so. Also, try multiple ground wires. The currents to ground from all the capacitors in the filter flow through that ground connection, and if it has much inductance it will have a voltage drop that limits the rejection of the filter. If you have the connectors available, a better connection method is to solder an SMA connector shell directly to your ground plane at the input and another directly to the ground plane at the filter output. Then connect the center pins of the connectors to the input and output and connect your cables. If you just have some SMA pigtails (or can make a couple by cutting an SMA cable in half), you can connect the shield of a pigtail to your ground and the center wire to your input and similarly connect an output pigtail. Then connect those pigtail connectors to the NanoVNA. As others have mentioned, making all the component leads as short as you can will help, but the grounding is probably the bigger factor at this point. --John Gord |
Re: Help with LPF Measurement
Hi Jim,
Thank you for your suggestions. I will shorten leads and properly dress the components tomorrow. BTW I had no 270 caps but had 50s and 220s, hence the two caps in parallel. You make a really good point in saying "the filter's not working right...." But what I don't understand is why the results from the sig generator/oscilloscope show the filter is filtering out high frequency harmonics pretty well, but the NanoVNA shows a very weird S21 result. It improved slightly when I added the ground leads between the board and the test rig (my bad for missing that!!), but it's not even close to what it should look like. Onwards....Thanks again. Best, Mitch NK3H |
Re: Help with LPF Measurement
Alan,
I agree 100% on neatness, lead length, etc. This was supposed to be just a test project in anticipation of properly building the filter. From your comments and others', it appears I need to use appropriate methods from the very start in order to get results even in the ballpark. Advice appreciated. Thank you. |
Re: Help with LPF Measurement
Dave,
Thank you for your reply. Very much appreciated. In order: 1) Done. 2) Yes, I measured all components with my LCR meter (DE 5000). 3) Correct. 50 ohms confirmed by others for this filter. 4) It's possible that some capacitors aren't right for this frequency range. I'll look into that. 5) I posted the S21 imaged from the VNA, not the SAVER program. I'll work on that next. 6) Signal generator does not sweep; that's a good idea and will try to figure something out. Thanks for your help. I'll spend most of tomorrow working on this. Best, Mitch NK3H |
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