The Mysteries of the Pi Network Explained

[@ianbaines8140]

That was a very useful lecture and many thanks professor. I have been an electrical engineer for 50 years and hold a Masters in radio engineering. Been a ham even longer and have built many tube circuits that use the pi network. I honestly could not figure out how it worked. An impedance transformer, a tuned circuit plus a low pass filter - but how does all this magic happen with only three components? All is now revealed and it is pretty obvious once explained. Believe it or not I could not find a decent explanation in all my reading. So thanks for walking us through it so well. Now if I could only figure out the formulas needed to design one.

[@johncherish7610]

Absolutely clear and fully understandable, you make it easy for even novice operators to understand how it works. Brings back the early years in high school when I studied electronics, back in the vacuum tube era (1968 ) " back in a day" and my old Heathkit DX60B Transmitter I built and wish I still had. I remember tuning it up even to this day on those cold winter evenings KB3QHD

[@udylevy]

Awesome video! I love explanations like this, where the lecturer explains the idea clearly instead of drowining you in endless calculations. well done!

[@garylanders1470]

Excellent examples and explanations! Thank you kindly Sir.

[@russpeck1320]

As a long-time ham and electronics technician with college training, your explanation of the tank circuit has finally answered questions that I have had for years. More of this stuff, please, Greg!

[@w2tty]

I’m amazed at how effective your explanations are. Nice job. Clear, and it makes sense. Thank you.

[@LousyPainter]

Wow! You're a fantastic instructor. Thanks for your consideration to take the time to explain this so clearly.

[@Doonit_hard_way_since_65]

Really well done. Great explanation of a confusing subject with a completely simple method. Hats off.

[@rojmt]

Thank you! I appreciate how you broke down the diagram first before rearranging it in the form that it's most usually known. In that way, we can see the function of the circuit first and how it came to be like the final schematic. I enjoyed this leacture, thanks so much!

[@livesonjura]

Fascinating to see how the pi network evolved from a simple resonant circuit. And how practical considerations come into play as you replace the expensive roller inductor solution with a cheaper variable cap in series with the existing cap to perform the needed current & voltage transformation and still maintain resonance. It makes good sense now. Thank you.

[@terencebarfield5864]

Sir I am seriously enjoying your presentation

[@garysewell5465]

At last...the tank circuit explained in a way I understand...thank you

[@w9fgh]

Clearly and simply explained. It would also be good to explain why a Pi network network reduces harmonics.

[@davidwest2773]

Excellent explanation thank you so much I'm studying for my ham extra level four

[@Simon-mz7sf]

Thankyou for such a concise and clear tutorial

[@borisromanoff4244]

Great class, dear Professor. Please give us more classes like this very one.

[@antoniohenriques7156]

Great lectures only come from great professors. I love it as I love your home made "stuff". Happy new year Greg, and keep up the good work. THANK YOU! CT1CXD 73's

[@AB1Vampire]

How nice to see you on YT. I've benefitted from your online articles many times. n2eye

[@fpaolo63]

thanks... a great explanation 👌 ... without hard math. A good refresh also for an old electronic eng. that spent his life working on digital stuff....

[@woodjim]

(Reposted in the right place) FINALLY! An easy-to-understand explanation of this great impedance-matching method. No math, no Smith Chart (which I could never figure out!)... just a clear, methodical explanation of what's going on that any sixth-grader ought to be able to understand. The ONLY reservation I have is, at the end, the connection of the tapped inductor. The schematic shows that you're shorting the turns you don't want to use, which I think would mess things up badly. So just open up the right-hand end of the coil... right? Thanks for this! And please do more, keeping them simple for guys like me.

[@glatta0]

No!!! Keep the unused turns shorted. Otherwise, the coil acts as an autotransformer stepping up the voltage to very high values on the open end. This can easily cause arcing and burnout. I know this from personal experience.

[@glatta0]

I forgot to mention that the reactance of the shorted turns keeps the shorted current to a reasonable value, limiting the power dissipated to a small amount.

[@woodjim]

@@glatta0 Well, we disagree here. Yes, the coil's an autotransformer, but better to have a step-up with no load than a dead short across what's essentially a secondary winding. Try this on an old TV power transformer: use it as a filament supply and then short the high voltage winding. I smell smoke!

[@glatta0]

@@woodjim Jim, I smell smoke too. You are absolutely right about the TV transformer. I think you would see smoke too! That is because the resistance and reactance of the transformer secondary are very low at 60 Hz. However, we are at radio frequencies here, not 60Hz. Imagine leaving the tank coil open as you suggest, and connecting an RF choke across the unused turns. Very little current will flow because of the reactance of the RF choke, even though the DC resistance of the choke might be very small. That is what happens when you directly short the unused turns, except that the unused turns have high reactance at RF and themselves serve as the RF choke. To double check I found that every amplifier in the 1965 ARRL handbook has the unused section shorted, as does Collins in their 30L-1 amplifier. The unused turns are also shorted in my 813 amplifier and 6146 amplifier, and both of those amplifiers work great.

[@woodjim]

@@glatta0 Well then, I stand corrected, Greg, and thank you for delving into this to obtain a definitive answer. But regardless, despite what the science might say, if Collins got away with it, that's good enough for me! They had some beautiful and remarkably simple designs that consistently gave superb performance.

[@steveoshaughnessy3736]

Wish I'd seen this when, as a high school kid, I was trying to tune my HW-101. This is so simple. Especially the description of a tank.

[@arthurhunt642]

I've had a few HW101's. They were great and I made quite a few DX contacts with a dipole 30 feet up and usually well under a 100 watts. Back then 15 meters was so quiet you could hear a pin drop and if I could hear them I could work them. This would have been around 1997 I think..

[@DH478]

Great video, excellent explanation. More of these would be greatly appreciated.

[@G0USL]

Excellent explanation, Thanks for that.

[@robertholland7457]

Yes, very usefull, 71 years old and still learning !

[@Blueglow]

Excellent explanation. Well done!

[@markengelsen8091]

You're a good teacher

[@andrzejpl9897]

Wanderful explanation .Thank you professor .

[@DavidDoonan-bh9sq]

Thank you for the wonder full presentation

[@ericdaine4982]

Such an inspiration! Thank you so much. This is very useful to me and helps my understanding as I pick up my first novice station. Great Timing!!! I have been gathering pieces to build a 90W RF amp based on the documentation on found on your web page. This novice transmitter I am reviving also has a 6146 final output tube and this video is a very good complement. Thanks again for the effort, its very appreciated.

[@arthurhunt642]

You mean Technician class. All they have now is Technician, General, and Extra.

[@ericdaine4982]

@@arthurhunt642 Yes Technician for me but Novice for them when the transmitter was made. The transmitter I am reviving would most likely have been built as kit by a Novice in the 60's If I ever do get it going again I will be using it as a Technician. Thanks for pointing out the change.

[@PapasDino]

I've always struggled on how best to present this concept to students...plagiarism is the sincerest form of flattery and I hope you won't mind me using your outline in the future (as well as pointing folks here to view this great presentation!). 73 - Dino KLØS

[@robatkinson5672]

Two initial inaccuracies: Many hams use balanced line and link coupled networks today. It's not true that their use ended following WW2. But, their use did decline. Balanced line is found today in SW BC stations using dipole curtains and rhombic antennas because the line loss is less over a wide frequency range. Hams can take advantage of this too if they have room for only one balanced antenna but want to use it for multiple bands. Some link coupled matching networks attenuate harmonics.

[@glatta0]

I use balanced feeders myself.

[@mikefahey6606]

Very nice presentation. Helped me with something I'm working on. You should have an 'about' on your channel.

[@barryfitchew6378]

Great video, good job

[@JamesCopple-ACUASI]

Thank you for demystifying this.

[@terencebarfield5864]

Question: what is the formulae in placing our Antenna up off ground at specific frequency

[@chrisreich40]

To clarify - the circulating current in the parallel circuit does not increase. Because the voltage is increasing, the current must reduce. If it didn't, the passive components would be generating power, which of course they cannot do. I'm sure this was a slip of the tongue, but I offer the clarification so as not to confuse those who were paying close attention. To restate; the voltage developed in the resonant components increase as a result of more power being applied to the source, but the current is reduced so that the power from the source remains the same as the power in the parallel resonant circuit.

[@billjones2271]

I thought this video might be a waste of time. I was wrong. Thank you sir.

[@terencebarfield5864]

Question : what governs the antenna thickness in relation to the 50 watts RF output Transceiver

[@frankbaron1608]

excellent lecture

[@w2tty]

Way better than anything the ARRL has on this subject!

[@bobbydrummond420]

Dr. Latta is the bomb! I'd venture to say that it would be hard to find another Pi Network explanation better than the one above. Thank you, Dr. Latta, for one heck of a job and for your service to the Amateur Radio community!

[@claytonvedder2287]

Excellent explanation!

[@terencebarfield5864]

Sir I do like your presentation

[@ahmedzafar-xp3kb]

Thank you Sir. It is very helpfull

[@johnhess351]

Wow, now I understand! You got through to me.

[@OptionParty]

Very good, I enjoyed that. Question: With the band switch, it shorts the end turns. Is it better to leave the end float ? Does the shorted turns add a load, absorbing some of the power from the source ?

[@OptionParty]

@@WirelessMuseum Wow again. Thanks for taking the time for this answer.

[@OptionParty]

@@WirelessMuseum An open end would develop high voltage like a Tesla coil.

[@glatta0]

Keep the turns shorted. Otherwise, the coil acts as an autotransformer stepping the voltage up to very high values, potentially causing arcing and burnout. The reactance of the shorted turns helps keep the current and power dissipated to an acceptable amount. I have found this through personal experience.

[@glatta0]

@@WirelessMuseum The reactance of the shorted turns keeps the current down to a small value keeping the power dissipated to a minimum. In my 813 amplifier I neglected to short the unused turns and burned out my 80m toroid twice before I realized what I had done! Live and learn...

[@garypoland5288]

Great video, thanks!

[@theduckisok]

More please.

[@davidspivey6298]

How I know what a PI-netlooks like .thankyou

[@wayneswift541]

thank you

[@timmcilraith8762]

Brilliant. Thanh you.

[@kamilsp7]

Awesome !

[@W1ZY]

Brilliant. Feynman lives.

[@robt7785]

Best explaination ever!!!!!

[@userMJ813]

thanks!

[@springer9406]

Who knew that George Carlin was also an electrical engineer! :)

[@rickeaston3228]

It's too bad that the gentleman did not explain the operation algebraically using the formulas for Q to be able to calculate values for the caps and coil to make a working pi network that matches the right impedances together.

[@bobbybrooks4826]

LC

[@StephenCooteNZ]

Thank you ! Best wishes from New Zealand. ZL3ABX

[@alecdvor]

Ty for this detailed explanation kq4ijy