1:1, 9:1, 49:1 Matching Units - What's the difference?

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1:1, 9:1, 49:1 Matching Units - What's the difference?

Рет қаралды 19,708

3 жыл бұрын

When do you use a 1:1, 9:1 or a 49:1 balun?
Our Ask An Elmer panel discuss this question - what's the difference between matching units?
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Пікірлер: 28

@mabs-O_o 3 жыл бұрын

No one addressed the actual common use cases... 1:1 is normally used as a balun to turn coax into a tuned dipole antenna 9:1 balun is normally used to 450 ohm balanced antennas like the T2FD 9:1 unun was commonly used to match a random end fed to a *tuner* - this is the lazy man's match and used on a lot of 27MHz CB base station vertical antennas 49:1 is normally used as an unun for end fed *half wave* antennas

@mabs-O_o 3 жыл бұрын

I should also mention that the random end fed is where most end fed antennas got a bad reputation; it isn't a half wave.

@neilmartin112 3 жыл бұрын

Thank you

@stevet7522 2 жыл бұрын

Thank for answering that. I was confused when none of them actually gave an answer like this.

@rickmckee6698 2 жыл бұрын

The problem with using a 9:1 unun with a tuner and a random wire for multiband operation is the fact that the 9:1 sometimes converts the impedance down too low which causes higher losses in the tuner. Lets say the antenna impedance on a particular frequency is 20 ohms, that 9:1 unun is going to convert that down to 2.2 ohms which is almost like a dead short to the tuner causing losses to increase. Also, since the 9:1 is most efficient when feeding a 450 ohms load, losses in the 9:1 also increase. Yes, you will make contacts with it, but not as solid as you would with a properly tuned antenna!

@nealbeach4947 26 күн бұрын

Rule #1 Never overthink a dipole antenna.

@KD9ZHF 17 сағат бұрын

You have a nice extensive library of videos. I find myself coming here as my reference! Thank you!

@HamRadioDX Сағат бұрын

Thanks! I appreciate that, I'm glad they are helpful

@hubercats 2 жыл бұрын

Should this question come up again, it might be helpful to mention that ratios such as 1:4, 1:9 and 1:49 arise because their square roots yield integral numbers of turns which is convenient, at the very least, for building transformers. Likewise, it might be helpful to mention that, for example, a 1:49 impedance ratio can be matched by a transformer with a turns ratio of 1 to 7 (i.e., square root of 49), or one with a turns ratio of 2 to 14. I.e., it’s the turns ratio that matters. - Cheers! - Jim (KK7CSC) PS: Here’s a specific example thatI think drives home my comments above: Imagine wanting to match an antenna impedance of 2500 Ohms to a 50 Ohm feed line. This suggests an impedance ratio of 50 to 1. Since the square root of 50 is 7.07, which is not a particularly friendly turns ratio, you would choose 49 which is close enough to 50 and has a square root of7 which yields an integer turns ratio (7:1).

@0150r 2 жыл бұрын

Thanks for explaining that. I was wondering how the antenna kit I built had 3 to 21 came out to be a 1:49 unun. It makes sense now.

@rickmckee6698 2 жыл бұрын

A 9:1 is designed to feed a 450 ohm load and is most efficient when doing so. And there is no such thing as a "driven element" in a coax feed line. RF is basically an AC signal, so there is no positive and negative terminal as the polarity changes back and forth at the frequency of operation. But, to RF there is basically "THREE" conductors in a coax feed line ! Yes, 3 ! You have the center conductor, the inside of the shield, and the outside of the shield. The good current which is known as differential mode current flows on the center conductor and on the inside of the shield. The bad current which is called "common mode current" is the nasty energy that flows on the outside of the shield and can wreak havoc on your equipment in the form of increased receive noise, and distortion on your transmitted audio and other nasty such as a hot microphone that can give you a shock if you touch it with your lips and it happens to be a metallic mic. The 1:1 Guanella current balun at the feed point of the antenna and another one right before the coax enters your shack can help eliminate these issues!

@chillychurchil5972 Жыл бұрын

EFHW 40m band(about 20m long)used 49:1 unun will performed better compare to 9:1?

@alvarogaitan2529 5 ай бұрын

4:1???

@javierpolendok5mhc 2 жыл бұрын

Not enough information on this video sorry

@democratpro Жыл бұрын

STOP EATING fat man!

@paulp1204 2 жыл бұрын

An electrical engineering question answered by a self described amateur radio newb and a mechanical engineer. Turns out not to explain the subject correctly. Who Knew? It's the square root of the turns ration. (Notice that 4:1, 9:1, and 49:1 are all squares?) So a 49:1 give a change in impedance by a factor of 7. Not 49. Good guess though. Seriously, why pose as an educator on this if you haven't even read the basics yourself, or have any practical experience?

@HamRadioDX 2 жыл бұрын

Glad you liked the video!

@paulb9179 2 жыл бұрын

Yeah no kidding. And they didn't even address what a 49:1 was used for in relation to a 9:1 yet the description says they do. 3 minutes of my life I will never get back.

@rickmckee6698 2 жыл бұрын

Then why does the 49:1 transformer convert a 2450 ohm impedance to 50 ohms? Looks like a 49 times change to me! Try it with a 2450 ohm non inductive resistor connected to the 49:1 and have it on an antenna analyzer if you have one and you will see the facts!

@paulp1204 2 жыл бұрын

@@rickmckee6698 Hi Rick - the confusion might be because a 49:1 matching unit is not the same as a 49:1 transformer. You are correct - a matching unit will work as you say. A transformer ratio is a statement of the number of turns. This ends up being the same as the voltage ratio (and the inverse of the current ratio). Now, the power is the same on either side of the transformer (a and b), so if you look at the general power formula P=V^2 / Z (power equals voltage squared divided by impedance), then (Va)^2 / Za = (Vb)^2 / Zb. This can be re-written as Za/Zb = (Va/Vb)^2. So the impedance ratio changes with the square root of the voltage ratio, i.e. a 49:1 transformer changes the voltage down by 49 and the impedance down by 7.

@rickmckee6698 2 жыл бұрын

@@paulp1204 Matching unit, transformer, whatever you want to call it still "transforms" 2450 ohms down to 50 ohms ! Just like a 9:1 changes 450 ohms to 50 ohms and a 4:1 does the same with a 200 ohm load. It doesn't matter what you call it. So please explain what you mean by "matching unit" how is it made" 2 primary turns and 14 secondary turns ? If that's what you can a "matching unit, I have built several of them for various power levels and they all convert 2450 ohms to 50 ohms ! The 7:1 ratio is the winding ratio - not the impedance ratio. It has 1 primary turn to 7 secondary turns, and you still have the same winding ratio if you use 3 primary turns to 21 secondary turns. but the impedance transformation is still 2450 ohms to 50 ohms or 49:1.

@kevinkc3onohelijeepworld953 3 жыл бұрын

Better ? Would be which mix???😆 31 43 j material k composite Omg way to much knowledge in just iron cores & the mixes them add in windings 😳☺️😆KC3ONO

@user-yt7cg8kf9z 4 ай бұрын

In terms of performance, a ratio of 9:1 or 49:1 yields nearly equal results, yet both function optimally with vertical antennas ranging from 5.2 to 16 meters or longer. However, it is essential to use FT 240-43/61 for superior performance. height allways helps lot better performance - G7UNF.