Current vs Voltage BALUNS

[Master Chief]

In a recent post about a KLM antenna, it appeares a 1:1 Voltage BALUN made by Van Gordon was incorrectly used and it got me thinking.

I am a HUGE fan of CURRENT BALUNS. Walter Maxwell and others praise the use of CURRENT BALUNS and explain WHY they are better.

On the other side of the fence was Lew McCoy (SK). He was a VOLTAGE BALUN fan. I sat in on one of Lew's talks about BALUNS and it was very interesting to hear his side.

W4COX sais on his website:

FIRST AND FOREMOST A BALUN PROVIDES A SMOOTH TRANSITION BETWEEN THE UNBALANCED FEEDLINE AND THE BALANCED ANTENNA. TRANSITION MEANING ISOLATION. WITHOUT A BALUN, THE FEEDLINE WILL TRY TO BECOME PART OF THE ANTENNA.....

This tells me we should all run 1:1 BALUNS at the base of our antennas.....especially those who run A-99 and iMax 2000s! Some of us already do!

Here is what Cebik has to say:
http://www.cebik.com/a10/ant47.html

There are MANY websites that cover topics on BALUNS. You should check them out!

If you need to buy one, Radio Works and W4COX have some quality units.

 

[Robalo]

this is what i found : BALUN deliver the power to your antenna with minimum loss and perform a perfect transition from balanced to unbalanced. This results in the strongest signal your antenna’s capable of producing with the lowest SWR under given conditions

 

[FL Native]

without a proper groundplane on the a99 or the imax the balun would not be a good idea. unless you put it say 12-15 feet down the line.

 

[DXman]

I was going to make a balun today and attach it to the beam, I was going to use 18' around a 6" piece of PVC, but after reading what Cebik was saying I guess I would only need to go with about 6' for the 10 meter band (of course 11 meters for me).

Anyway Master Chief thanks for the link, glad I caught that in time.

 

[Toll_Free]

I was going to make a balun today and attach it to the beam, I was going to use 18' around a 6" piece of PVC, but after reading what Cebik was saying I guess I would only need to go with about 6' for the 10 meter band (of course 11 meters for me).

Anyway Master Chief thanks for the link, glad I caught that in time.

6 to 10 turns, about a foot across (diameter) will give you an effective balun for CB use.

You want these turns not cobbled up, but run next to each other. I use a can as a former, then tape each individual turn to the one next to it. This is called a solenoidal choke. Much better than the typical just run 10 turns in a loop and tape it all together.

Ever wonder why they just don't cobble up all the chokes in your radio into one turn on top of another?

--Toll_Free

 

[C2]

I made me one of those, 8 turns around a 6" plastic form, hot goobered and taped together all nice and neat like. One at the antenna feed and one at the radio. Feeding my MacoV58.

I don't know if it made a difference, but I can still talk a long way just like before. I never had TVI problems before either and SWR comes in at under 1.1 with a good looking curve.

 

[DXman]

So how's it look...Ok I hope.
6 turns on a 6" dia.

 

[Toll_Free]

So how's it look...Ok I hope.
6 turns on a 6" dia.

That's the idea.

Two things:

1. It needs to be a foot in diameter, not 6 inches.
2. On a beam, it needs to be below the lowest point (the vertical element, or the hanging (drooping) elements on a Gunn or Gizmotchy style antenna)

The point is to get the currents off the outside shield of the coax.... If the balun is on the boom, you will find that you can still get currents on the outside just because of the braid being bombarded with RF....

--Toll_Free

 

[Toll_Free]

So how's it look...Ok I hope.
6 turns on a 6" dia.

Oh yeah, remove the coil form as well. Some PVC exhibits a tendency to heat up with RF.



--Toll_Free

 

[Robalo]

i going tried this one is only $32.95

http://unadilla.com/w2dinline.htm

 

[DXman]

1. It needs to be a foot in diameter, not 6 inches.
Picture below courtesy of KC2NXV shows using 2 pvc couplers joined and glued using about 2 inches of 4 inch PVC pipe, so the couplers would adhere and be stronger.

]
This doesn't look like a foot in dia to me
2. On a beam, it needs to be below the lowest point (the vertical element, or the hanging (drooping) elements on a Gunn or Gizmotchy style antenna)

The point is to get the currents off the outside shield of the coax.... If the balun is on the boom, you will find that you can still get currents on the outside just because of the braid being bombarded with RF....

--Toll_Free

All thou it may look like it is attached to the boom, it is not. There will be a 2" gap when the beam is brought up in the horizontal.

 

[Toll_Free]

1. It needs to be a foot in diameter, not 6 inches.
Picture below courtesy of KC2NXV shows using 2 pvc couplers joined and glued using about 2 inches of 4 inch PVC pipe, so the couplers would adhere and be stronger.

This doesn't look like a foot in dia to me
2. On a beam, it needs to be below the lowest point (the vertical element, or the hanging (drooping) elements on a Gunn or Gizmotchy style antenna)

The point is to get the currents off the outside shield of the coax.... If the balun is on the boom, you will find that you can still get currents on the outside just because of the braid being bombarded with RF....

--Toll_Free

All thou it may look like it is attached to the boom, it is not. There will be a 2" gap when the beam is brought up in the horizontal.

I'm not sure where this was supposed to go, but....

For a choke style balun to work at 27 megs, it needs to be 12 inches across, and 6 to 10 turns.

Period.

If you want, I'll go grab my books and give you a mathematic lambasting with theory and all that will prove my point, and lose most everyone around here, serve nothing more than to waste bandwith, and people will probably go store bought.
Don't believe me, get a ARRL manual.



And any amount of PVC can be RF sensitive. Put the piece of PVC your going to use into the microwave with a cup of water and nuke it for a minute.

Pipe hot? If so, it reacts to RF and don't use it. I found this out the hard way building a LowFer station in high school.

--Toll_Free

 

[Master Chief]

I'm not sure where this was supposed to go, but....

For a choke style balun to work at 27 megs, it needs to be 12 inches across, and 6 to 10 turns.

Period.

If you want, I'll go grab my books and give you a mathematic lambasting with theory and all that will prove my point, and lose most everyone around here, serve nothing more than to waste bandwith, and people will probably go store bought.
Don't believe me, get a ARRL manual.

Instead, how about a Volume #, Chapter, and page. I've never seen or heard of a 12" coax balun. One would think the lower the frequency the larger ther balun and the 6" to 8" diameter cores seem to be what all the books say.

Also, Force 12 uses PVC a LOT! Maybe there are issues at microwave frequencies, but not so below 30MHz. I DON'T KNOW!