All About Baluns (Ask Dave #73)

Music is "Sour Tennessee Red," by John Deley and the 41 Players, courtesy YouTube Music Library.

Twitter: @dcasler

[georgelasko]

I just wanted to thank you for all of your videos.
One thing nice about this hobby is people helping others.
Thanks again, and 73.

[oldbassist]

From one grey bearded ham to another, "very well presented. Thanks." I'll be watching more. After almost 60 years in the field, and 40 years of not operating at all, baluns have always eluded my understanding of them. Hardly ever needed one but I'm back building antennas and I have no idea what I'll be trying next. Now with the internet sleep will be my only distraction. I finally picked up an MFJ Z-bridge like you show and that will be a lot of fun to play with. 73's OM.

[Ryan-xcuh]

This is the video that got me to connect the dots from my electrical knowledge to my lacking antenna/balun knowledge. Thank you sir.

[pupeno]

I have a novice argentine license (LU5ARC), an extra american licence (AC1DM) and a foundation british one (M6UON) and only just now watching this video I understood choque baluns. Thank you Dave.

[ericdee]

Smart Man right here, reminds me of my Father silent key (k6hzh) who was also a amature extra and a radar engineer for Lockheed Aircraft from 54' to 78' these guys are the pioneers of the ham radio hobby!🇺🇸⚡

[reedreamer]

Excellent work OG - I think your best work is with these advanced concepts, thorough and nuanced.

[davids]

Dave, you are a blessing! Thank you for sharing your experience and wisdom!

[rodneyseiwald]

Hi Dave,
In your animation starting at 1:38, you show current flowing back and forth on the center conductor, but no current flowing on the shield. However, there is current flowing on the INSIDE of the shield, and it is equal and opposite to the current on the center conductor. So there should be two arrows going in opposite directions INSIDE the coax. There must be a return path somewhere, and we don't want it on the OUTSIDE of the shield. That's why we might want to use a choke balun.
Keep up the good work! 73 de kc0tw.

[adventuresofbobandlana]

Dave, you are a real asset to Amateur Radio. N7KHH 👍🏾

[philt]

Dave - I think you should review your statements regarding coax starting around 2:30. The shield in fact is the second conductor in this RF AC circuit; you have to have at least 2 conductors in a circuit. You can't have a single conductor simultaneously being the supply and return path. RF current equal and opposite to the current in the center conductor does flow on the 'shield'. Ideally, the shield current will be confined to the inner surface of the shield due to skin effect- the surface that can 'see' the center conductor

[TechTins_Projects]

with reference to 8:17 I think the reason is same as why power lines use very high voltages. High voltage means smaller currents. With long cables the I squared losses will reduce the power to the end of line. But using a transformer to convert the signal to a high voltage means proportionally lower current, this 4:1 hence reduces those I squared losses. eg P=IxIxR. My guess is at the arial end, that 4:1 is simply converted back to 50ohms. It means you can have much longer cable as far less I squared losses will occur.

But that is a wild guess as I know bugger all about transmission lines.

[WILL]

Thanks for breaking this down. I still want to learn more about baluns and ununs, but this video got me thinking about them in a different way. I understand so much more about antennas now.

[liminal]

Fantastic video - I learned a lot - Thank you @David Casler - btw, animations that show what's happening 'in the wires' is really helpful!

[laserhobbyist]

4:1 Baluns are useful between balanced lines for center fed Zepps, Off-center fed (OCF) dipoles with coax, G5RV antennas, full wave loops, NVIS dipoles that are close to ground and have impedance levels near 200 ohms or high impedance feeds for log periodic beams.

[elemsit]

I will definitely have to watch this one several times...

[mrmrlee]

My understanding is this; if an antenna is not balanced, current (or signal/RF/voltage it's all the same idea) flows back along the shielding of the cable (or one leg of a feedline) to the transceiver. This back flow produces a high SWR reading which can damage the receiver if not corrected. Makes sense so far?
A balun which is an RF choke, a line wrapped around a toroid core, absorbs and dissipates this RF before it returns thereby producing an acceptable SWR reading.
The reason there are different ratios of baluns is because the amount of turns, equaling RF absorption, is different depending on how unbalanced the antenna is.
More unbalanced=more windings around the core=more RF absorbed. That's it!

[tglenn]

Thank you. You're the first person I've heard to give a good, coherent, understandable explanation of this whole topic.

[noth]

Awesome! Pure gold, thank you very much, now I finally understand what it is, what it's for and where/how to use one. 73 from NL

[brucesmith]

Very nice presentation. I appreciated that you pronounced the word BALUN correctly. Sometimes they are called “balms” (that’s an ointment) or “balloons” which only adds to the confusion about these devices.

[michaelhiggins]

Some really great info here, and presented at a level that you don't need to be a Broadcast Engineer to understand. Well done and thanks from KM2U ;)