Quarter wavelength impedance matching (2/2)

[@joeteejoetee]

Excellent math, drawings, and explanation! Thanks for making a PCB to prove the science.

[@AndyFletcherX31]

Thanks for this video, for the first time I am beginning to understand how stub matching works

[@juliussokolowski4293]

In practical antenna VSWR measurements you see scalloping (oscillation in the VSWR plot) quite often. It confuses the heck out of some people. That is caused by there being a reflection (more or less severe missmatch) somewhere down the line - usually at the antenna feed-point. The feed-line acts like a quarter wave stub. Your demonstration shows another pitfall, impedance converges towards 50 ohm as the feed-line loss increases with frequency, with enough feed-line loss you can have almost anything look like 50 ohms. Lesson is, don't characterise antenns over long, lossy feed-lines.

[@rs4425]

Wow. Outstanding.

[@CisterJr]

fantastic web lecture!!

[@kensmith5694]

An interesting point about folded dipole antennas is that they are two quarter wave stubs with shorts at the ends resulting in a high impedance.

[@m1geo]

Excellent video!

[@joesoap2014]

Lovely job, thanks.

[@mustafahussien5010]

Very nice demosteration

[@Cien_Swiatla]

thx for the vid

[@PCBWay]

Good job as always!! 👍

[@joaopaulocoelho5401]

Perfect video!!

[@ionkolkhuistanke1313]

Hi, I've tried registering as a patreon supporter however I keep getting "You can’t join this creator’s membership." after checkout. Do you have any idea how I could fix this?

[@FesZElectronics]

Hello! I currently took a pause from video making for the month of December; as part of this pause I put patreon payments on hold, so no existing patrons are charged, and new ones cannot join. This will change starting next year if you are still interested.

[@ionkolkhuistanke1313]

@@FesZElectronics Great! Thanks and enjoy your holiday.

[@mikehibbett3301]

Brilliant. Thank you

[@thathalfthaiguy]

Would really love to see you make and tune a quarter length primary Tesla coil system!

[@szekerespista3758]

Yes! I am interested too 👍

[@kensmith5694]

Isn't the secondary the part with the wavelength that matters.

[@thathalfthaiguy]

@@kensmith5694 Yes, they BOTH matter according to Tesla.... the primary is a quarter of the secondary by "electrical" length. Tesla specified this for the best operation of his Tesla coil. The way people operate so called Tesla coils are not what Tesla did, he knew what he was doing and he knew what was important. The modern "Tesla coils" are a far cry from the original. It is not only important to get correct frequencies but also correct length. They are basically coupled antennas if operated properly.. and not just tuned tank circuits. There are major differences between the two..

[@kensmith5694]

@@thathalfthaiguy I wouldn't call them a coupled antenna because that really has little meaning. The primary side often is resonated with capacitors to bring it into a match with the natural frequency of the secondary coil. The coupling factor for the transformer action needs to be very near critical coupling if you want good power transfer. This means height and diameter matter.

[@thathalfthaiguy]

​@@kensmith5694 You say only height and diameter matter? They do (as far as high Q is concerned) but go look at Tesla's original coil and you can clearly see visually that they are nothing like the modern ones that are really a perversion of how Tesla originally designed them. Tesla did not use tall skinny secondary coils, his secondary was squarish and with a relatively low number of turns. US Patent No. 645576 "The length of the thin-wire coil in each transformer should be approximately one-quarter of the wave length of the electric disturbance in the circuit, this estimate being based on the velocity of propagation of the disturbance through the coil itself and the circuit with which it is designed to be used." If one knows what Tesla was doing then one would know they are more like coupled antennas, hence the importance of length. But if one just want sparks and what everyone today is doing, then it's not important for that person. But not everyone is content with these toys and wish to do something closer to what Tesla originally had in mind.

[@davidwillmore]

Don't striplines and microstrip lines need to have ground pours to their sides as well?

[@FesZElectronics]

That is not mandatory - the impedance is usually defined in reference to the ground planes; having ground left and right will help with preventing cross coupling to other traces though

[@LiJohn-yi6wz]

What's the name of pcb software,it looks like very beautiful.

[@FesZElectronics]

Its "Circuit Maker"; the free version of Altium

[@openFrimeTv]

Hey Tell me, did you tell somewhere about a 50 ohm resistor in series with the generator and parallel to the analyzer?

[@kensmith5694]

Yes, he showed the 50 Ohm load on the output side. His generator is likely 50 Ohms.

[@openFrimeTv]

@@kensmith5694 I mean, is the resistor connected in series or in parallel with the generator?

[@kensmith5694]

@@openFrimeTv If you think of the generator as a voltage source then the resistor is in series with that voltage.

[@openFrimeTv]

@@kensmith5694 Thanks

[@kensmith5694]

@@openFrimeTv BTW: The bit about "voltage source" was because if you think of it as a current source then the resistor is in parallel. I will explain hoping you can follow this: Imagine the output of the generator is a single PNP or P-MOSFET transistor with the signal taken off the collector/drain. The 50 Ohms would be connected to ground. The transistor would produce a pulse of current that doesn't depend on voltage so its impedance would be extremely high. That high impedance would be in parallel with the 50 Ohms. I hope this helps you to see. If not I can try further if you say where I lost you.