Antenna Briefs #5 - Electric Fields, Magnetic Fields, and EM Waves

This video focuses on understanding electric, magnetic, and electromagnetic fields produced by antennas. This knowledge will be essential in future antenna topics, but we also provide some key engineering results here. For example: How do we find the field strength in volts/meter produced by an antenna and how do we map that to the voltage that a receiving antenna produces? How can we build transmitters that obey regulatory rules? A brief preview of the next episode is also provided, where we ask the questions: what is a B field (spoiler: it's really just an E field in another relativistic frame of reference), and how do we calculate and simulate far-field patterns from antennas...

[@michaelgallias2651]

Your whole channel makes KZbin a richer place. Please don't stop making such videos!

[@MegawattKS]

Wow - that's a wonderful comment. Thanks so much !

[@W1RMD]

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.

[@MegawattKS]

Thank you so much for the kind words !

[@gerardoalonso1177]

Great video!, i will be looking forward for the next one.

[@MegawattKS]

Thanks !

[@emailuser3869]

Another wonderful video. Thanks and please keep up the good work. 73

[@MegawattKS]

Thanks! I appreciate the comments. It helps with motivation :-)

[@alklapaxida850]

Regards from VK3, thank you,

[@wd8dsb]

Fantastic content and very helpful, thanks.

[@MegawattKS]

You're very welcome. 73's !

[@johnbarber1482]

best explanations!!! Thank you!

[@MegawattKS]

You're very welcome! Sorry for the late reply.

[@johnbarber1482]

@@MegawattKS oh no worries, I'm surprised you had time to rely.

[@rjordans]

Nice and clear explanation again, thanks! 73 de PA3RJ

[@MegawattKS]

You're welcome, and thanks so much for the comment ! 73

[@robballantyne3]

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 KZbin 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

[@MegawattKS]

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).

[@robballantyne3]

repo should be available now. Thank you!

[@robballantyne3]

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!

[@roberthipple7431]

I was looking for Episode #6, and then I just noticed that these are all new episodes. Is episode 6 on its way?

[@MegawattKS]

Yes. I just got a little delayed in finishing it. Hopefully it'll be done in a couple/few days 🙂

[@roberthipple7431]

@@MegawattKS Looking forward to it. Keep up the good work!

[@MegawattKS]

Episode 6 should be up and visible now. Thanks again for the comments and your interest in the material !

[@georgethomas8138]

Is it possible to print out the slides for reference?

[@MegawattKS]

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')

[@MegawattKS]

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 :-(

[@Abhinav-db1qu]

excellent playlist , i saved it . Are you present on instagram

[@MegawattKS]

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.

[@Abhinav-db1qu]

@@MegawattKS got it 👍