You are an excellent professor! Makes me wish I went to college, but I'm learning more now at 50 years old than I ever would have when I was younger, plus you have a way of making these very complex ideas less frightening. My time here is well spent and I enjoy every second of it. Thanks for everything you do.
Hi @MegawattKS, I have a question if you don't mind answering --- if it's out of scope please disregard (I'm not even sure CZcams will warn you I've left this here). I'm attempting to design a 10MHz bandpass filter (as part of a larger project to build an HF WWV receiver). I've used one of the web based design tools and designed a Butterworth 3-pole filter with 3-dB points of 9.5MHz and 10.5Mhz and 50ohm termination. I've built the circuit out of parts that I think are reasonable for 10MHz frequencies and have reasonable Q values, low ESR. I've measured the filter with a NanoVNA and the insertion loss is huge, about 20dB. I've built it on a protoboard and dead-bug style and the results are quite similar. The Inductors had a Q of about 60 and DCR in the 100s of milliohms. The caps were thin film caps with Q's over 200. I suspect I'm making some fundamental error that maybe you'll spot immediately. If it's not really apparent, maybe you have some advice about what to try and diagnose first, ... Anyways, no worries if I'm asking too much, please don't feel any qualms about ignoring the question if I am asking too much. Thanks, Rob
I Rob. Interesting problem. I actually love troubleshooting, so I'll try to help for sure. Can you provide a link to the web based design tool page and/or otherwise specify what the topology of the filter is? Is it a coupled-resonator design, or does it involve two parallel LC sections with a series LC in the middle perhaps? And what are the LC values? Also, aside from the insertion loss being high, can you detect any other anomalies in the measured response that might provide some clues? E.g. does it have the right shape when you measure S21 or does it show some non-flat passband behavior (e.g. two distinct peaks)? Finally, one way I often try to troubleshoot such problems is to look at S11 and S22. Sometimes if there's a connection issue or an SMD cap failed due to thermal shock, S11 and S22 can give hints (although you mentioned two different builds has similar issues - so that kinda rules that out).
Sorry, I'm having problems with adding comments. I thought I left the following but I couldn't find it after I returned: ------------------- @MegawattKS thank you so much. I wasn't expecting such a gracious offer. I'm going to setup a github repository to share the PDF of the filter design with you. Unfortunately, my computer chose this moment to update it's development environment (including git) so it may take a bit. I used rf-tools.com/lc-filter/ to design the filter. I chose Butterworth/Bandpass/3 pole/ "Conventional, Series-First" so the design appears to be a series resonator, a parallel resonator to ground, and a series resonator. The appearance of the VNA measured S21 parameter looks about right to me just too much insertion loss. The S11 parameter also looks about what I might expect with a notch downward at the same frequency as when S21 maximizes (however, I'm guessing the notch doesn't go low enough). I'm guessing I can look at S22 and S12 by reversing the physical ports. Is that right? If so, we ought to see the same because the network is reciprocal (because it's linear) right? The git repo ought to be available at: github.com/ballanty/filter once I get things uploaded. I'll add the PDF of the filter design and some notes. Many thanks again!
Hello, When an electromagnetic wave strikes a receiving antenna, the electric field of the wave causes electrons to move up and down. What about the magnetic field of the wave? How does it affect the receiving antenna?
That's a very good question. I honestly don't have a good answer, other than to say that the full mathematical analysis may be required to illuminate this. In the final analysis, its an EM wave, so electric and magnetic fields are both involved. For the dipole antenna we're discussing, the electrons move in the antenna mostly due to the E-field excitement. At least that's the easiest way to visualize what's happening. But this is going to create currents and generate a magnetic field of it's own - which then interacts with and changes the overall E and B fields coming into the antenna's vicinity. But that's as far as my intuition goes. Even if the full mathematics of field analysis is done, it may be tricky to say what effects the B field is creating in the receiving situation. Perhaps someone else reading these comments may have insights to share...
@@MegawattKS what do u mean by (But this is going to create currents and generate a magnetic field of it's own - which then interacts with and changes the overall E and B fields coming into the antenna's vicinity) is the magnetic field coming out of the receiver antenna duo the oscillating interact with the electromagnetic waves coming in ?
@@medolol550 Yes - that's one way of conceptualizing it. But not just the B field. Also an E field is 'coming out'. When I did a Google search for "plane wave field distortion near a receiving dipole", the AI answer says it slightly differently - but equivalently: "When a plane wave encounters a receiving dipole antenna, the electromagnetic field near the dipole can become distorted, particularly in the "near-field" region, due to the interaction between the incoming wave and the dipole's own electric and magnetic fields, causing variations in the field strength and polarization depending on the dipole's orientation and the distance from the wave source.". (NOTE: Generally I don't trust everything an AI 'thinks', but sometimes it is good at expressing things :-) The Google AI text references a Wikipedia article as well as something called Energy Velocity and Reactive Fields journals. I didn't dig inside to see where it got the information to synthesize its response from this. But the statement has to be true. Otherwise the EM plane wave would pass the receive antenna unchanged - which is not possible because the received signal power had to come from somewhere 🙂
@@MegawattKS u know i have finished a full electromagnetism course but the point about electromagnetic waves is not clear at all , like duo to special relativity there is nothing called magnetic field , duo to quantum electrodynamics there nothing called electric field even its just the effect of the virtual photons , i just wanna be professional at electromagnetic waves i dont know how to be like this cuz of that so how to be like this cuz of that confusing so u know a way?
Hi. Thanks for the comment and question. Unfortunately no. I studied spherical coordinates and some of the main math solutions using them long ago - but as an engineer I never had a place to apply that - so I'm afraid I can't offer anything there. Sorry.
I don't have them on a website currently - but am starting to work on that thanks to your comment. I'll try to reply again if/when I get that done. Thanks for the inquiry. 73's (ham radio speak for 'best wishes')
Finally got the website built out and the slides uploaded. If you're still interested, they're here: ecefiles.org/rf-design/ Unfortunately, they will use up a lot of ink if printed, as I didn't find an easy way to set everything on a white background :-(
Your whole channel makes CZcams a richer place. Please don't stop making such videos!
Wow - that's a wonderful comment. Thanks so much !
You are an excellent professor! Makes me wish I went to college, but I'm learning more now at 50 years old than I ever would have when I was younger, plus you have a way of making these very complex ideas less frightening. My time here is well spent and I enjoy every second of it. Thanks for everything you do.
Thank you so much for the kind words !
Great video!, i will be looking forward for the next one.
Thanks !
Another wonderful video. Thanks and please keep up the good work. 73
Thanks! I appreciate the comments. It helps with motivation :-)
Regards from VK3, thank you,
Fantastic content and very helpful, thanks.
You're very welcome. 73's !
best explanations!!! Thank you!
You're very welcome! Sorry for the late reply.
@@MegawattKS oh no worries, I'm surprised you had time to rely.
Nice and clear explanation again, thanks! 73 de PA3RJ
You're welcome, and thanks so much for the comment ! 73
I was looking for Episode #6, and then I just noticed that these are all new episodes. Is episode 6 on its way?
Yes. I just got a little delayed in finishing it. Hopefully it'll be done in a couple/few days 🙂
@@MegawattKS Looking forward to it. Keep up the good work!
Episode 6 should be up and visible now. Thanks again for the comments and your interest in the material !
Hi @MegawattKS,
I have a question if you don't mind answering --- if it's out of scope please disregard (I'm not even sure CZcams will warn you I've left this here).
I'm attempting to design a 10MHz bandpass filter (as part of a larger project to build an HF WWV receiver). I've used one of the web based design tools and designed a Butterworth 3-pole filter with 3-dB points of 9.5MHz and 10.5Mhz and 50ohm termination. I've built the circuit out of parts that I think are reasonable for 10MHz frequencies and have reasonable Q values, low ESR. I've measured the filter with a NanoVNA and the insertion loss is huge, about 20dB. I've built it on a protoboard and dead-bug style and the results are quite similar. The Inductors had a Q of about 60 and DCR in the 100s of milliohms. The caps were thin film caps with Q's over 200.
I suspect I'm making some fundamental error that maybe you'll spot immediately.
If it's not really apparent, maybe you have some advice about what to try and diagnose first, ...
Anyways, no worries if I'm asking too much, please don't feel any qualms about ignoring the question if I am asking too much.
Thanks,
Rob
I Rob. Interesting problem. I actually love troubleshooting, so I'll try to help for sure. Can you provide a link to the web based design tool page and/or otherwise specify what the topology of the filter is? Is it a coupled-resonator design, or does it involve two parallel LC sections with a series LC in the middle perhaps? And what are the LC values? Also, aside from the insertion loss being high, can you detect any other anomalies in the measured response that might provide some clues? E.g. does it have the right shape when you measure S21 or does it show some non-flat passband behavior (e.g. two distinct peaks)? Finally, one way I often try to troubleshoot such problems is to look at S11 and S22. Sometimes if there's a connection issue or an SMD cap failed due to thermal shock, S11 and S22 can give hints (although you mentioned two different builds has similar issues - so that kinda rules that out).
repo should be available now. Thank you!
Sorry, I'm having problems with adding comments. I thought I left the following but I couldn't find it after I returned:
-------------------
@MegawattKS thank you so much. I wasn't expecting such a gracious offer. I'm going to setup a github repository to share the PDF of the filter design with you. Unfortunately, my computer chose this moment to update it's development environment (including git) so it may take a bit. I used rf-tools.com/lc-filter/ to design the filter. I chose Butterworth/Bandpass/3 pole/ "Conventional, Series-First" so the design appears to be a series resonator, a parallel resonator to ground, and a series resonator. The appearance of the VNA measured S21 parameter looks about right to me just too much insertion loss. The S11 parameter also looks about what I might expect with a notch downward at the same frequency as when S21 maximizes (however, I'm guessing the notch doesn't go low enough). I'm guessing I can look at S22 and S12 by reversing the physical ports. Is that right? If so, we ought to see the same because the network is reciprocal (because it's linear) right?
The git repo ought to be available at: github.com/ballanty/filter once I get things uploaded. I'll add the PDF of the filter design and some notes.
Many thanks again!
Hello,
When an electromagnetic wave strikes a receiving antenna, the electric field of the wave causes electrons to move up and down. What about the magnetic field of the wave? How does it affect the receiving antenna?
That's a very good question. I honestly don't have a good answer, other than to say that the full mathematical analysis may be required to illuminate this. In the final analysis, its an EM wave, so electric and magnetic fields are both involved. For the dipole antenna we're discussing, the electrons move in the antenna mostly due to the E-field excitement. At least that's the easiest way to visualize what's happening. But this is going to create currents and generate a magnetic field of it's own - which then interacts with and changes the overall E and B fields coming into the antenna's vicinity. But that's as far as my intuition goes. Even if the full mathematics of field analysis is done, it may be tricky to say what effects the B field is creating in the receiving situation. Perhaps someone else reading these comments may have insights to share...
@@MegawattKS what do u mean by (But this is going to create currents and generate a magnetic field of it's own - which then interacts with and changes the overall E and B fields coming into the antenna's vicinity) is the magnetic field coming out of the receiver antenna duo the oscillating interact with the electromagnetic waves coming in ?
@@medolol550 Yes - that's one way of conceptualizing it. But not just the B field. Also an E field is 'coming out'. When I did a Google search for "plane wave field distortion near a receiving dipole", the AI answer says it slightly differently - but equivalently: "When a plane wave encounters a receiving dipole antenna, the electromagnetic field near the dipole can become distorted, particularly in the "near-field" region, due to the interaction between the incoming wave and the dipole's own electric and magnetic fields, causing variations in the field strength and polarization depending on the dipole's orientation and the distance from the wave source.". (NOTE: Generally I don't trust everything an AI 'thinks', but sometimes it is good at expressing things :-) The Google AI text references a Wikipedia article as well as something called Energy Velocity and Reactive Fields journals. I didn't dig inside to see where it got the information to synthesize its response from this. But the statement has to be true. Otherwise the EM plane wave would pass the receive antenna unchanged - which is not possible because the received signal power had to come from somewhere 🙂
@@MegawattKS u know i have finished a full electromagnetism course but the point about electromagnetic waves is not clear at all , like duo to special relativity there is nothing called magnetic field , duo to quantum electrodynamics there nothing called electric field even its just the effect of the virtual photons , i just wanna be professional at electromagnetic waves i dont know how to be like this cuz of that so how to be like this cuz of that confusing so u know a way?
@@MegawattKS and how can i contact with u privatly if u dont mind
Hi I’m a novice rf engineer new to the channel. Your presentation skills are wonderful. Do you ever have a lecture about spherical near fields?
Hi. Thanks for the comment and question. Unfortunately no. I studied spherical coordinates and some of the main math solutions using them long ago - but as an engineer I never had a place to apply that - so I'm afraid I can't offer anything there. Sorry.
Is it possible to print out the slides for reference?
I don't have them on a website currently - but am starting to work on that thanks to your comment. I'll try to reply again if/when I get that done. Thanks for the inquiry. 73's (ham radio speak for 'best wishes')
Finally got the website built out and the slides uploaded. If you're still interested, they're here: ecefiles.org/rf-design/ Unfortunately, they will use up a lot of ink if printed, as I didn't find an easy way to set everything on a white background :-(
excellent playlist , i saved it . Are you present on instagram
Thanks. No - sorry. I try to keep all discussions in the comments so that everyone can hopefully benefit. Feel free to ask technical questions there.
@@MegawattKS got it 👍