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topbuzzuk
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Wire antenna questions
hello, i was just wondering what the best kind of wire is to use building, probably a 1/4 wave antenna in the loft. also how do you go about gettin as good a bandwidth you can(low mid high)? anyone got any links to diagrams or info? cheers
Paddy
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11/Mar/2008, 10:00 pm
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yamanx1
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Re: Wire antenna questions
I can do this for you, just give me a good idea of the size of your loft, and I'll work something out for you 
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11/Mar/2008, 10:05 pm
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topbuzzuk
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Re: Wire antenna questions
i'll have a measure tomorrow dave, i think its about 9-10 foot high and the room to play with is 20 x 20 foot give or take a few low bits in roof space.
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11/Mar/2008, 10:27 pm
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soundmanjim
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Re: Wire antenna questions
your just about ok. one vertical element made out of stripped back mains wire, 4 9 foot radials out of more stripped wire, something heavy on the bottom and hang it from a hook at the apex, spread the groundplanes out, solder the inner of the coax to the upright and join the g/plane wires together and solder the outer to taht - should work a treat. vertiocal bit should be about 9'6"
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11/Mar/2008, 11:48 pm
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yamanx1
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Re: Wire antenna questions
I think the best performance for space and for indoors is going to be a loop antenna. A wire one of these will only take a couple of hours to make and minimal materials required.
Theres loads of weird and wonderful loop antennas here, if you fancy building one I'll help where I can, I can certainly lay my hands of the bits
Clicky link
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21/Mar/2008, 7:57 am
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Hot Fusion
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Re: Wire antenna questions
Tips on improving bandwidth.
Two ways this can be done:
Increase the diameter of the vertical element drastically - I'm talking about using a piece of aluminium scaffold/antenna mount tubing or metal drainpipe for the element. Can be done, and works well. Bit of a bugger to fine tune though due to the cutting bit...
The other is to use two verticals next to each other, both connected together to the inner of the coax at the lower end and slightly separated at the top. Cut to slightly different lengths to reflect the frequencies you wish to cover.
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24/Mar/2008, 12:56 pm
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yamanx1
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Re: Wire antenna questions
Found this:
Loft wire antenna, simple dipole, but with a bit more detail of how to build it for 11m
clickerage to wire dipole
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25/Mar/2008, 8:47 am
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topbuzzuk
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Re: Wire antenna questions
cheers dave, that is one of the easieest explanations ive read on the net. i'll have to get some wire sorted and have a go
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25/Mar/2008, 11:41 am
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topbuzzuk
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Re: Wire antenna questions
howdy, ive been puting a wire antenna up in the loft and really want some help. i could of made a simple 1/4 wave but decided to try and make a 1/2 wave(2x17'ish elements). now swr seems to be a problem unless i only have the center pin of coax plug connected to swr meter, this tells me there is a short but both patch leads are fine and so is the coax to the antenna. ive been reading about 1/4 dipoles and something to do with the ohms at feedpoint. any ideas help or pointers that may help me out apreciated 
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Home:Icom 706MK2G-Heil HMM-IC mic-Inverted V ant(indoor)
Mobile:Ranger VR9000-Astatic Teardrop mic-Zetagi B300P amp-Moonraker SC5000 ant
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16/Apr/2008, 4:15 pm
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Hot Fusion
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Re: Wire antenna questions
Is this antenna for 11 metre use? If so, the lengths are wrong. You need to have two wires of approximately 8'6" long, one attached to the coax outer, the other to the inner.
You SWR the antenna by trimming EQUAL amounts off the ends (or adding it...).
Ideally you should include a choke balun to eliminate RF on the coax outer and to force the antenna to act in a balanced manner. I expect there's a bit of info on choke baluns about if you google for it.
For the record, I'm about to fit up an inverted 'V' in the loft - no idea yet how it will perform due to the slate roof, but I suspect it will be easily as good as anything else I can get up there.
I'll take some photos when I do it and post them if anyone's interested.
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16/Apr/2008, 9:06 pm
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