topbuzzuk
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Inverted V 11m 1/4 wave
i have finished installing my homemade 1/4 wave inverted V, its in my loft running down the apex either side of roof. i used 12 gauge speaker wire and i have a 9 foot balun at the rig end. swr is cool right through low mid high, 01 low 1.2, 01 mid 1.3 and 1.4 on 01 high. thats more bandwidth than my boomerang, i'll have to let you know how it works when skip allows 
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26FB118
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17/Apr/2008, 10:19 pm
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yamanx1
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Re: Inverted V 11m 1/4 wave
Brilliant 
Got any pics?
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18/Apr/2008, 6:40 am
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topbuzzuk
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Re: Inverted V 11m 1/4 wave
i'll scramble up the loft when i get back from IOWight and get some pics of it, cant wait to try it out
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26FB118
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18/Apr/2008, 7:30 am
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Hot Fusion
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Re: Inverted V 11m 1/4 wave
What's the nature and design of your balun at the rig end?
I always understood a choke balun as close to the antenna as physically possible was the way to go with this type of balanced antenna, to prevent RF on the outer of the coax, but I'm always open to new ideas and theories!
EDIT:
I've just taken a photo of the balun I made for my inverted 'V', for those interested. Now I've just got to get it up in the loft...
Last edited by Hot Fusion, 21/Apr/2008, 7:28 pm
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21/Apr/2008, 7:10 pm
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yamanx1
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Re: Inverted V 11m 1/4 wave
As a balun yes, balancing feedline to antenna. But really this is a RF Choke as you have said, and can be used to great effect to stop RF from being emitted from the outer of the feed line, causing interference
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21/Apr/2008, 7:51 pm
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topbuzzuk
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Re: Inverted V 11m 1/4 wave
the balun/choke was put at the radio end to solve rf feedback on my boomerang, its part of the coax so as i'm using the coax for the V its in there.
feedpoint of V, plastic car body-filler spreader, socket off amp and a couple of bits of alloy bracket to take the stress off the solder joints/wire oh and 12 gauge stranded wire
choke/balun, plastic bottle, 9 foot coax winding and insulation tape(i did think of putting plugs on it so i could remove it and use elswhere)i will one day))
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26FB118
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21/Apr/2008, 8:58 pm
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Hot Fusion
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Re: Inverted V 11m 1/4 wave
Quote yamanx1:
"But really this is a RF Choke as you have said, and can be used to great effect to stop RF from being emitted from the outer of the feed line, causing interference"
Correct, but as it prevents RF from flowing in the outer of the coax, it also forces the currents in either leg of the antenna to be equal - they have no choice in the matter, and therefore the ideal radiation pattern of the antenna is preserved.
This is common practice, and better than a transformer balun which may well suffer from overheating of the core at high power levels, something an air-cored choke won't suffer from. In fact, I'm not aware of an argument for not using a choke balun, apart from physical size.
Obviously, if a transformation of impedances is required, then a transformer balun is the obvious choice, but for 1:1? Choker all the way!
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22/Apr/2008, 8:32 pm
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yamanx1
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Re: Inverted V 11m 1/4 wave
Thanks for that, good information. It wouldnt hurt, therefore to have one at each end of the coax feedline?
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22/Apr/2008, 8:46 pm
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Hot Fusion
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Re: Inverted V 11m 1/4 wave
Wouldn't hurt at all, except for the tiny additional loss caused by the couple of extra metres of coax wound into the choke, which is pretty small.
Don't see a need for it though, as a balun at the antenna end effectively isolates the coax, meaning you simply don't need one at the TX end.
Since we started this balun discussion, I had a poke about in the web thingy and found the following page, which pretty much answers most questions I reckon:
http://www.hamuniverse.com/balun.html
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22/Apr/2008, 10:11 pm
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topbuzzuk
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Re: Inverted V 11m 1/4 wave
so i guess i would be best to make a new balun and stick it at antenna end for best radiation pattern? that was a good link, had a good read
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23/Apr/2008, 10:01 am
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