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Marconi
Advanced Member
Username: Marconi
Post Number: 579
Registered: 11-2001
| | Posted on Thursday, February 02, 2006 - 9:51 am: | 
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833, you mentioned among these current threads in Antennas a new term for most of us, a bazooka balun, sleeve, or whatever, that is used on this great little antenna to help decouple the feed line from the antenna.
In my recent study of this bazooka device, I read that the proper design should include insulating the top of the bazooka sleeve from the antenna, and that the coax shield should also be physically brought back to ground at a point 1/4 wavelength away from the feed point at the far-end of the bazooka sleeve. Thus it is said that this balun will work as intended.
Of course the Starduster does not follow these detailed features in what it is doing in its assembly using a simple coax sleeve within the ground plane field below the radiator. In fact this sleeve is the only thing that is similar to a sleeved balun referred to as a bazooka.
I read about all of this idea many years ago and at the time I seem to recall a friend came up with an idea of adding a 108" coax jumper from the feed point of the antenna to the end of a 106" sleeve in the base of his Starduster. Of course we did not know a thing about a bazooka balun back then, even though I had read something similar in an article. The idea intrigued me without recalling any details. For me this only came together as an idea very recently on re-reading about the bazooka balun and finding the article published back in 1982. When you mentioned it here, I was taken aback and thus I ask you about this.
In this idea we used a barrel connector to reconnect the feed line. We then used a good stainless hose clamp to attach the barrel directly to the supporting mast the sleeve of the antenna was attached to. This had the affect of grounding the coax shield at a point 1/4 wavelength away from the feed point of the antenna.
We were very surprised to learn that this really worked to completely eliminate feed line radiation for this antenna. In his case he contends to this day that it also eliminated all of his TVI and the reputation that he had previously earned for having the worst bleeding antenna in the general area. Was such an idea like this, regarding the Starduster, ever made popular back then.
Do you feel that there is in technical merit to such an idea as we applied what we did to the Starduster?
Even though this sleeved idea (not our idea) used in the design of the Starduster was not as outlined in descriptions of the bazooka sleeve I have read about, do you feel Avanti's sleeve scheme (bazooka lite if you will) could have practical uses in other antenna designs to help stop feed line radiation?
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Georgeodjungle
New member
Username: Georgeodjungle
Post Number: 4
Registered: 1-2006
| | Posted on Thursday, February 02, 2006 - 2:00 pm: |
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the bazooka is one of the easiest ways to make a dipole.
also farrite does wonders for tvi, line loss & for making antennas.
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Tech833
Moderator
Username: Tech833
Post Number: 1185
Registered: 8-2002
| | Posted on Thursday, February 02, 2006 - 9:39 pm: |
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'Bazooka' is a generic term for a decoupling device, just like 'Kleenex' is generic for facial tissue.
A decoupling sleeve is called a bazooka when it actually is not, it is just a decoupling sleeve. That is what I was talking about in the other thread. |
Marconi
Advanced Member
Username: Marconi
Post Number: 582
Registered: 11-2001
| | Posted on Thursday, February 02, 2006 - 11:11 pm: |
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Well 833 the only way you can make that statement is in reference to the sleeve used on the Starduster, which does not comform completely to the design of a bazooka line balancer. It is those very differences that I attempted to make clear in my post above. Apparently you missed that. But thank you for your opinion, it is after all better than no opinion at all. No need to respond, I'm napping. |
Tech833
Moderator
Username: Tech833
Post Number: 1187
Registered: 8-2002
| | Posted on Friday, February 03, 2006 - 10:44 am: |
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Not at all. Let me respond.
Is IS O.K. to use that reference on more than just the Starduster since it also appears in several commercial antenna catalogs to describe sleeve dipoles and other colinear antennas with stacked elements and generic sleeve decoupling schemes to decouple feedline RF.
Also, a few ferrite catalogs I have here use the term 'bazooka' when referrring to using ferrites to isolate feedline radiation.
Any time RF current flows over the outer surface of coax cable and you remove it in some way, someone will always call that a 'bazooka'. Just the way it is... |
Forummaster
Moderator
Username: Forummaster
Post Number: 446
Registered: 11-2001
| | Posted on Friday, February 03, 2006 - 8:26 pm: |
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Posted for Marconi
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Tech291
Moderator
Username: Tech291
Post Number: 354
Registered: 11-2004
| | Posted on Friday, February 03, 2006 - 8:38 pm: |
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Marconi,
from the Collins radio collector site;
tvi and bazooka
Tech291
CEF#291
KC8ZPJ |
Marconi
Advanced Member
Username: Marconi
Post Number: 583
Registered: 11-2001
| | Posted on Friday, February 03, 2006 - 10:03 pm: |
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Thanks ForumMaster for posting this photo for me.
Paul the bazooka balun I refer to is at the top of the page left. The link I referred to above is as follows.
An Analysis fo the Balun
You will note in this article page 1 that there is described there a bazooka balun exactally like the photo that the FM posted for me out of the ARRL Antenna Book, 1974. It may be true that bazooka is typically referred to in a generic form, but the examples I note in this thread are what I was referring to in speaking about its application in the Starduster antenna. It may be that these issues are a thing of the past as to importance, but it has peaked my interest non-the-less. |
Tech833
Moderator
Username: Tech833
Post Number: 1193
Registered: 8-2002
| | Posted on Saturday, February 04, 2006 - 8:44 am: |
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The ARRL antenna book is just full of mis-used phrases and words too.
If the sleeve is open at the bottom, it is a decoupling sleeve. If it is shorted at the bottom, it is a band pass style decoupling sleeve.
Either way, it is common to refer to each as a 'bazooka'.
I think we beat this one into the ground by now. |
Marconi
Advanced Member
Username: Marconi
Post Number: 587
Registered: 11-2001
| | Posted on Saturday, February 04, 2006 - 10:28 pm: |
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You know 833 I have a saying that I post in my signature on a praticular forum. It goes like this;
quote:They use a bunch of nice words to gives us good advice and then with a couple of more special words, they takes it all back.
We were so close to getting the answer to what is the difference. You spelled it out so well and then took it all back with those special words I mentioned, band pass decoupling and just plain old decoupling. Is this a professional teaching technique to get us to think or just to •••• us off.
I agree, "I think we beat this one into the ground by now." Thanks for going the extra little bit to get us all past the hump. |
