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Tech808
Moderator
Username: Tech808
Post Number: 9046
Registered: 8-2002
| | Posted on Sunday, January 22, 2006 - 9:29 am: | 
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Copper Forum Members,
Below you will find several posts form other Topics & Members that have been moved to this  Topic.
This has been done to help keep the other topics on track with the Original Question that was asked and to help those seeking advice on BALUNS find a single area for that advice.
Thanks,
Lon
Tech808
CEF808
N9OSN |
Bruce
Senior Member
Username: Bruce
Post Number: 3414
Registered: 9-2003
| | Posted on Sunday, January 15, 2006 - 11:14 pm: |
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marconi....
MYSELF ....
I like bazoka balum a fold back of sheild back up the coax but its not broadband .... |
Bruce
Senior Member
Username: Bruce
Post Number: 3411
Registered: 9-2003
| | Posted on Sunday, January 15, 2006 - 6:25 pm: |
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I found they work and are cheep .... |
Marconi
Advanced Member
Username: Marconi
Post Number: 517
Registered: 11-2001
| | Posted on Sunday, January 15, 2006 - 8:12 pm: |
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Well Chad said his choke stopped his common mode currents also, I just never saw any affect.
I know how to stop them from coming into my shack, but it doesn't stop them at the feed point and that is where I tried, several times, to get one of these chokes to work.
Bruce how do you determine these currents? What did you do to tell the currents were originally there and then when the were no more? |
Marconi
Advanced Member
Username: Marconi
Post Number: 520
Registered: 11-2001
| | Posted on Monday, January 16, 2006 - 10:33 am: |
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But Bruce, how do you tell if you need a balun and if it is working? Is it if the hair stands up on the back of your neck or not? That is supposed to be funny and is not serious. |
Marconi
Advanced Member
Username: Marconi
Post Number: 537
Registered: 11-2001
| | Posted on Thursday, January 19, 2006 - 2:03 am: |
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Hey Bruce, I am however really serious about the question though. I would like to hear your method of determining if we need a balun or not, and then how do we tell if it has worked or not. |
Bruce
Senior Member
Username: Bruce
Post Number: 3432
Registered: 9-2003
| | Posted on Thursday, January 19, 2006 - 10:33 am: |
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How i do it here is see if i get RF back into this room ....the room is solid alumin a big fariday sheild.... the balums on SOME antennas like my ringo and the Diamond v-2000 cut the readings ( i use a Field strengh meter next to the coax shield) so thats the way i show if MINE is having a effect. |
Marconi
Advanced Member
Username: Marconi
Post Number: 543
Registered: 11-2001
| | Posted on Friday, January 20, 2006 - 7:26 am: |
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Hey Bruce thanks for the info on how to determine for us if you have common mode currents, and what you use to determine if you have solved the problem when using a balun or choke.
Personally I believe there are only a couple of antennas that we typically use in 11 meters on which a balun will work successfully to do what is intended by their use. Right off the top of my head, and based on what I understand about their use, it seems to me that only a 1/4 wave ground plane and a 1/2 wave dipole have the properties to effectively use a balun to solve the problem with common mode currents. I might include in this group a yagi with an insulated driven element and a quad radiator from the beam category of antennas as well. The primary reason I use here is that only these antennas are balanced and fed symmetrically with regards to their current distribution in the radiator and the ground side of the antenna (the two poles).
Unfortunately the antennas that we often use in 11 meters that need help in this area (CM currents) are not balanced, so therefore I see little chance for a balun or a choke to force those currents into a symmetrical state in order to help prevent common mode currents.
I will present a rather old published report as a source of information on the subject. I think that it will support my non-professional point of view on the idea I present.
An ANalysis of the Balun
This link is in Adobe format and you will need Adobe on your hard drive in order to read.
I make no claim that this source is the standard among all available, but it is the first information that I ever read on the subject many years ago and my thoughts on the issue have not changed over time. Most of the information that I consider here is on the first page and specifically in the first paragraph of the second column beginning with the words, “But coaxial cable is an unbalanced feed line.”
How say you?
Thank you Bruce again for getting back with your answer, I must have missed the post. BTW I also determine CM currents on the feed line or supporting mast as well by the use of a Field Strength meter. I believe it does a nice job of telling one what is going on right at the radio.
Marconi
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Bruce
Senior Member
Username: Bruce
Post Number: 3435
Registered: 9-2003
| | Posted on Friday, January 20, 2006 - 10:58 pm: |
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"just do as jo gunn says..."
I think they are full of it if the balum is below / away from the gamma match. ALSO why would you put a match facing DOWN the pole ??????? |
Marconi
Advanced Member
Username: Marconi
Post Number: 545
Registered: 11-2001
| | Posted on Saturday, January 21, 2006 - 9:10 am: |
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Bruce, I do not understand exactaly what you are getting at in your last post. Could you reword the statement to make the meaning more clear? |
Bruce
Senior Member
Username: Bruce
Post Number: 3437
Registered: 9-2003
| | Posted on Saturday, January 21, 2006 - 1:14 pm: |
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NO ......
Gama matches on a vertical elm do not produce equal current on both sides of the drivin elm.
SO facing it down would not make sence since your mounting pole would be on that side of the drivin elm. THIS IS WHY I RUN STACKED VERTICAL YAGIS on 2 meters and not one 8 elm .... it's a fact the pole interferes with the antenna when vertical......
It has nothing to do with the fact JOGUNN is JUNK. |
Marconi
Advanced Member
Username: Marconi
Post Number: 550
Registered: 11-2001
| | Posted on Sunday, January 22, 2006 - 10:00 am: |
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I want to thank you guys for this discussion. I have changed my mind about some things regarding my conculsion noted above at least. I won't try to explain, because I believe I just had too many things wrong in the post noted above as: Posted on Friday, January 20, 2006 - 7:26 am:
Now I have a better understanding of what a balanced antenna is, Thanks.
Bruce could that bazooka also take on the form of a sleeved dipole where the top of the balun tube around the coax is open and the bottom of the tube goes to ground with the coax shield at the bottom of the 1/4 wave tube (sleeve).
We use to make a 9' jumper that fed our old Stardusters. It ran inside the 9' support that goes inside the ground plane area below the hub of these antennas. For this discussion I refer to this as a bazooka balun. We used a barrel connector to hook this jumper and the balance of the feed line together a 1/4 wavelength below the feed point. Then we would use a stainless hose clam to attach the barrel connector physically to the supporting mast at the bottom of the bazooka tube. This brough the shield to ground a 1/4 wavelength below the feed point. It also stopped RF below these antennas when installed as noted and we thought that was all good.
Does this sound a little like what your refer to when you speak of a bazooka balun? |
Thehobo
Member
Username: Thehobo
Post Number: 57
Registered: 2-2004
| | Posted on Monday, January 23, 2006 - 2:07 pm: |
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mod. im not going there, but to me, one mans junk is anothers tresure!!!!!!!!!!!!!!!!!!!!!!!!!!!
thehobo
274150 am.
monitor ch. |
