Why a Balun on my dipole ?

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kb7uxe
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Location: roy,wa. 98580-0722
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Why a Balun on my dipole ?

Post by kb7uxe » Fri Mar 07, 2003 3:29 pm

Greetings from Dan. kb7uxe.
using an inverted V, with a 1:1 balun, set for 3.9mhz, using an MFJ 989c tuner
I was unable to tune anywhere except 75/80 meters.
When I removed the balun and replaced it with a simple center insulator,
I am now able to tune all bands...

What does that Balun do?

Why do i need that Balun ?

Why does the Balun limit my ability to tune other bands ?

Thank you.
Dan.
KB7UXE
Dan Asbjornsen
box 0722
Roy, wa. 98580-0722
kb7uxe@comcast.net
3.696 mhz CW most evenings sometime
between 7pm and midnight PST .

W0LPQ
Posts: 83
Joined: Wed Mar 05, 2003 4:51 pm
Location: Greenwood, IN

Balun

Post by W0LPQ » Fri Mar 07, 2003 7:05 pm

1. You have a single band antenna fed with Coax. If you want a multiband antenna, suggest you consider 450 ohm line with the tuner.

2. Single band antenna with balun trying to operate multiband, now the tuner has to tune the balun, coax as well as try to match the antenna. Impossible, darn near.

3. If you insist on using a balun, a better choice would be forget the tuner, add wires to make it a dipole for each band you want to use. This has been done before (as shown in earlier handbooks) and works well. The tuner is really not necessary if you operate on the bands the dipole is cut for. You can either use a balun or not. No real advantage, other than to realistically adapt the unbalanced Coax to a "balanced" antenna. Using multiple wires lets you get the SWR down to good levels in the portion of the band you want to use.

If you don't want to add wires, then #1 is the best route to go. Forget the balun and use just the tuner, but please use 450 ohm line. Makes it a whole bunch easier to tune. Some tuners have an internal balun that will convert the 450 ohm to whatever the tuner is happy with. Don't forget that whatever you put inline with the feedline to antenna path, the tuner has to tune. Individual wires for dipoles make it a whole lot easier and if you insist, insert the balun at the antenna. But you do not need a tuner. If you want the tuner, forget the balun.

73

Bill, W0LPQ

kb7uxe
Posts: 5
Joined: Fri Mar 07, 2003 3:00 pm
Location: roy,wa. 98580-0722
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balun...

Post by kb7uxe » Sat Mar 08, 2003 4:41 am

Thank you bill fro the information..
However,2 orignal questions are still unanswered...
1, what does a balun do?
2, Why do I need a balun?
3,Why does the Balun limit my ability to tune other bands ?
#3 I kinda read as: tuner can;t tnue coax, balun & antenna......
However, using coax, simple center insulator, a tuner and the mono band dipole
I can tune almost anywhere in the ham bands no problem....
I guess I'll just go with, Balun acks as a tuner or matching network (?)....
so when used it creates an envorement the tuner can't tune......

Isn't ham radio wonderful!!!!
Thanks, Dan,.
kb7uxe@yelmtel.com
8-)
KB7UXE
Dan Asbjornsen
box 0722
Roy, wa. 98580-0722
kb7uxe@comcast.net
3.696 mhz CW most evenings sometime
between 7pm and midnight PST .

W0LPQ
Posts: 83
Joined: Wed Mar 05, 2003 4:51 pm
Location: Greenwood, IN

Post by W0LPQ » Sun Mar 09, 2003 1:03 am

Roy, WA......my late uncle (W7HTR) lived there complete with windmill on his small farm.

1. Balun: Balanced to Unbalanced conversion. Either 1:1, 4:1, 9:1 or wind your own from various sites. A dipole is a Balanced antenna, and as many have said, a dipole can either use a balun or not use one. For years, they have been fed with Coax. Under normal conditions, a balun is not needed. Coax is unbalanced, thus, a balun..! The balun is NOT a tuner in any way shape or form. Its only "ack" act is to do impedance transformation and balanced to/from unbalanced sources/loads.

2. When you use a balun and try to "tune" the antenna, you introduce complex impedances and ... as you found ... complete havoc. I am not going into the math reasons why, but again, as you found, without the balun, you can tune it.

However, with a dipole and using open wire, now you can use the tuner and make it work darn near everywhere. Radiation from the openwire feeders and loss from the feeders ... is insignificant.

3. One should remember, that a dipole is a single frequency antenna. However it can be used on harmonics, as others have pointed out. The reason to use open wire feeders, is that due to the loss (or lack of it), the tuner really comes into its own and does what a tuner is supposed to do.

In my situation, I have 3 dipoles on one coax. 80/40/20 and no tuner. With 3 dipoles, now I can arrange them in the broadside direction I want, which is not the same for all 3.

73

Bill, W0LPQ

kb7uxe
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Location: roy,wa. 98580-0722
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balun ot no balun..

Post by kb7uxe » Mon Mar 10, 2003 4:18 am

Ok, Thanks for you help on this issue.
What I found out is, Without the balun, even the coax sheild is radiating rf
allowing the tuner to tune almost anywhere.....
When the balun is installed, it isolates the rf to the dipole only thus allowing only the dipole to radiate at rez frequency..
Thank you for all your comments and information.

Dan.
kb7uxe@yelmtel.com
8-)
KB7UXE
Dan Asbjornsen
box 0722
Roy, wa. 98580-0722
kb7uxe@comcast.net
3.696 mhz CW most evenings sometime
between 7pm and midnight PST .

JDALEY
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Baluns

Post by JDALEY » Tue Mar 11, 2003 10:17 pm

Do you need a balun?? Truthfully, no. A balun just takes an unbalanced feedline and allows proper feeding of a balanced antenna, such as a dipole. All coax is an imbalanced feedline.In theory, if NOT used, there will be current along the feedline. Also, pattern skewing will be present on the antenna. I have fed a dipole both ways, and have elected to use 450 ohm ladder line with a tuner. SWR losses are much less when the antenna is used on its nonresonant frequency. Since the balun is a 1:1 raio, there is no impedance change. Die hard designers will tell you a balun is preferred. Go buy some quality 450 ohm ladder line and just use the antenna whereever it will tune. It will be a very effective radiator. Keep in mind, that the presented SWR on a given frequency can be extremely high and all tuners dont work the same way. The impedance matching ability in ohms and reactance will vary from tuner to tuner. This applies only if you want to push the limits of the antenna. One of the best tuners is still the Heathkit 2060 and the TenTec 229 ( which I just purchased ). They offer an extremely wide matching range. This doesnt mean that all power is being radiated to the antenna-- it just means your radio can see 50 ohms on a wider range of non resonant frequencies.
Hope this helps. Joe N2GBT

N5JFJ
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You dont have to have the Balun... but I like using it

Post by N5JFJ » Thu Mar 13, 2003 11:55 am

Some great notes and remarks, here, great explainations...I agree that you do not have to have the Balun, but I will say personally that I really have had wonderful results in using them. Open feedline is great but because of the Pain, of damages in storms and winds, and Plain Old Twisting, Bracing, and just Rotting away, I prefer Coax again here. So with that said I've always found the greatest results for myself using the 1:1 Balun on my Dipoles. I even have inserted the 1:1 Balun on the Coaxial Bazooka's I've built (by adding them... where you cut the shield) and I have been asked time and time again what I use for an antenna. It works (For me) so well. and I am gonna stick my foot in it with this remark but...As far as antenna tuners go? I find it does MATTER also as to the antenna tuner matching device that you are using...Dear Lord! And for myself I've had much greater results with the Drake MN2000, The Dentrons, and Yes Especially Nye Vikings over these little 989C models that I've used. Both occasions I've used them I found them to be so TOUCHY, and almost Squirrely or Eratic!!! But again this is all just an opinion. For myself the Older Matching units are still the Best. That has soemthing to be said for Antenna Matching... and a new subject again...altogether. 73's & God Bless everyone. De N5JFJ
73's and May God Bless you and your Family

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