I've watched a lot of balun videos Dave, yours and many others, but there are still so many questions that either I don't understand the explanation to, or I can't find an explanation for...like the arrangement of windings that make one design a voltage balun, and a another design a current balun. And about the arrangement of windings, on a 49:1 unun, why are the first two windings of the 50 Ω input and one of the 2450Ω output wires, twisted together in most of the designs you find online? Are baluns/ununs more efficient than lumped LC matching networks at the feed-point for a single band antenna, what are the pros and cons of each? Ferrite rod designs seem to be easier to understand in laying out the wire turns, but is using a toroidal core more efficient, and what's with all those intricate wire wrapping arrangements for toroids? Also, is there a reason every unun, isn't simply designed as an autotransformer? And finally, I saw a design for a 4:1 air-core balun which the author said could handle more power than a ferrite core balun, if that's the case, why aren't there more balun designs that use no ferrite? ...and I won't even start to ask the questions I have about transmission line balun designs...
Thanks Dave. I have a balun that is made from PVC pipe that I think originally came from MFJ but the markings are long gone. I used and adapter and the 50 ohm calibration slug from my VNA and measured the resistance with my MKJ-269B. The resistance in the 80m band showed 50 ohms so it looks like I have a 1:1 ratio. Now how do I tell what type of balun it is? Is it a current balun or a voltage balun? An isolation balun? Can it be used to keep RF out of the feedline and shack? Thanks.
Does the very low reactive component you show at 3:52 for the Chameleon matching transformer mean that it is likely very broad-banded and have a low quality (low-Q) efficiency?
I know about using resistors and the values to test them. The one thing I'm wondering is it possible to use a Variable resistor and still get accurate results? And would it matter what type of Variable resistors used?
Those long leads are probably what's causing the reactance...Just connect the resistor right onto the transformer terminals...You can just count the turns to get the turns ratio, then square it to get the impedance ratio...3 turns / 2 turns = 1.5:1 turns ratio...1.5 squared (1.5 x 1.5) = 2.25:1 impedance ratio...50 ohms x 2.25 = 112.5 ohms output impedance.
Im renovating my radio room after 44yrs. In 1977 it had floresent light bulbs which caused noise in my HF reciever. I changed to incondesent bulbs. Im considering LED bulbs. Will it cause noise ?
oh, that's not antique at all. I wish I had that one.. still using the mfj 249 from the 90's, which works fine 😏 you can actually use mfj analyzers in sunlight, unlike those fancy but unreadable vna screens
I go with Balanced = Window/Ladder Line and UN balanced = Coaxial cable. UN (COAX) to UN (COAX) = UNUN and BalUn = Bal [ladder line] to Un [coax] balanced.
hi dave could you help i just made a fan dipole for 20 40m my centre feed point is at my bedroom window sil forward out to my back fence at 85 90 degrees apart will it be fine to use as a slopping away v down to 7ft off the ground yours mark thankyou
Not all toroids are balun. Most of the(4:1, 9:1, 49:1....) are transformers - only very few - maybe one is balanced to unbalanced. Some are just CMC filters.....
I use a VNA and a potentiometer to measure the ratio. Adjust the pot for minimum SWR, then measure the pots resistance. Ratio = resistance/50.
Wow that’s a good idea and simple. I will keep that in mind before purchasing a Balun.
I've watched a lot of balun videos Dave, yours and many others, but there are still so many questions that either I don't understand the explanation to, or I can't find an explanation for...like the arrangement of windings that make one design a voltage balun, and a another design a current balun. And about the arrangement of windings, on a 49:1 unun, why are the first two windings of the 50 Ω input and one of the 2450Ω output wires, twisted together in most of the designs you find online? Are baluns/ununs more efficient than lumped LC matching networks at the feed-point for a single band antenna, what are the pros and cons of each? Ferrite rod designs seem to be easier to understand in laying out the wire turns, but is using a toroidal core more efficient, and what's with all those intricate wire wrapping arrangements for toroids? Also, is there a reason every unun, isn't simply designed as an autotransformer? And finally, I saw a design for a 4:1 air-core balun which the author said could handle more power than a ferrite core balun, if that's the case, why aren't there more balun designs that use no ferrite? ...and I won't even start to ask the questions I have about transmission line balun designs...
Just the video I needed this week!
Thanks Dave. I have a balun that is made from PVC pipe that I think originally came from MFJ but the markings are long gone. I used and adapter and the 50 ohm calibration slug from my VNA and measured the resistance with my MKJ-269B. The resistance in the 80m band showed 50 ohms so it looks like I have a 1:1 ratio. Now how do I tell what type of balun it is? Is it a current balun or a voltage balun? An isolation balun? Can it be used to keep RF out of the feedline and shack? Thanks.
Is an antenna tuner something one would want if they are receiving only (i.e. SDR with long wire)? thanks
yes
Does the very low reactive component you show at 3:52 for the Chameleon matching transformer mean that it is likely very broad-banded and have a low quality (low-Q) efficiency?
I know about using resistors and the values to test them. The one thing I'm wondering is it possible to use a Variable resistor and still get accurate results? And would it matter what type of Variable resistors used?
Those long leads are probably what's causing the reactance...Just connect the resistor right onto the transformer terminals...You can just count the turns to get the turns ratio, then square it to get the impedance ratio...3 turns / 2 turns = 1.5:1 turns ratio...1.5 squared (1.5 x 1.5) = 2.25:1 impedance ratio...50 ohms x 2.25 = 112.5 ohms output impedance.
Good point. Thanks.
What is the difference between a current balun and a voltage balun and why do you need one vs the other?
How about measuring the Zo of a feedline. Such as home brewed open wire line ?
Im renovating my radio room after 44yrs. In 1977 it had floresent light bulbs which caused noise in my HF reciever. I changed to incondesent bulbs. Im considering LED bulbs. Will it cause noise ?
very informative
Nice antique antenna analyzer 🙂
oh, that's not antique at all. I wish I had that one.. still using the mfj 249 from the 90's, which works fine 😏 you can actually use mfj analyzers in sunlight, unlike those fancy but unreadable vna screens
If it's tapped asymmetrically would that not make it an UNUN?
I go with Balanced = Window/Ladder Line and UN balanced = Coaxial cable. UN (COAX) to UN (COAX) = UNUN and BalUn = Bal [ladder line] to Un [coax] balanced.
I may not be seeing this right without my glasses, but. I think I seen in the box the tap on 40, and in the spcs the tap was on 60. Is it me?
Dave, the documentation you showed from the manufacturer said 2.25:1, not 2.5:1.
Great vid though.
@@alanjhargreaves You must have been typing when he looked at his PC and read 2.25:1 The clarification was made.
hi dave could you help i just made a fan dipole for 20 40m my centre feed point is at my bedroom window sil forward out to my back fence at 85 90 degrees apart will it be fine to use as a slopping away v down to 7ft off the ground yours mark thankyou
my garden is only 7mt wide the hieght of my window is 28 feet high thankyou
Not all toroids are balun.
Most of the(4:1, 9:1, 49:1....) are transformers - only very few - maybe one is balanced to unbalanced. Some are just CMC filters.....
The technique shown only works for transformer baluns, not for choke baluns.