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 G3TXQ COBWEBB DESIGN 
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Hi steve, been looking at your cobby and i like the idea of single wire elements and the 1.4 tranny .. I was wondering if i could make this WITHOUT the traditional supports but having the elememts in a delta formation fed at the apex and supported with guy wires ?

billy

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Wed Nov 07, 2012 9:30 am
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 G3TXQ COBWEBB DESIGN 
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Billy,

I reckon that should be OK provided the angle between the wires on either side of the feedpoint doesn't become too narrow. The impedance seems to come out around 10-12 Ohms, so the match is still OK with the 1:4 balun.

73,
Steve G3TXQ


Wed Nov 07, 2012 10:01 am
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 G3TXQ COBWEBB DESIGN 
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Thanks steve ..

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Wed Nov 07, 2012 10:45 am
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 G3TXQ COBWEBB DESIGN 
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well decided to go the whole hog and make a cobby to your design steve, ordered a center plate today from AMTOOLS as to make this myself would cost not far off what he wants £17.50 after sourcing the steel , hardware and fuel etc ...

i need two 61 cores from him but will get them later . i noticed he is selling a 1:4 tranny using what looks like standard wire , i noticed your site stating 2 x 50 ohm cables in parrallel which is the way i will go but wondered if these are actually suitable ..

billy

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Voice is for CBers, amateur radio operators, the average citizen, and the military. In other words, voice is for everyone with a mouth. CW is for those who choose this newer mode of communication. Newer? Why yes. Voice has been around for a million years.


Thu Nov 08, 2012 2:27 pm
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 G3TXQ COBWEBB DESIGN 
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Post Re: G3TXQ COBWEBB DESIGN
Billy,

Interesting!

I had a chat to him about those baluns at the National Hamfest and took some of his wire home to try one. The bad news is they make a terrible 12 Ohm/50 Ohm balun because they introduce an impedance transformation due to the windings having the wrong Zo. The good news is that you can compensate by tweaking the lengths of the dipoles. They are obviously a lot easier to build than the twin-coax version, so I'd give them a try.

However ........ I noticed his wiring instructions were completely wrong - he'd got the high impedance side connected to the antenna and the low impedance side connected to the radio. I eMailed him about it, but don't know if he's corrected it yet in his instructions. Just make sure that the end of the balun where the two chokes are wired in series goes to the radio side.

By the way, there's nothing special about his wire; so why not buy the two cores, which you need anyway, and try some wire stripped from house wiring. You can always go back to coax if all else fails.

73,
Steve G3TXQ


Thu Nov 08, 2012 2:58 pm
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 G3TXQ COBWEBB DESIGN 
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For what it's worth i may as well do it your way steve , i need some 174 anyway for an MMD and the cores also .. I was just curious about the tranny using " normal" wire and thought if that was a better option i would imaging that's the way you would of gone ..

your explination of the transformer is very good anyway which was a relief as i have never made a Guanella balun before .. ( too tight to use 2 cores ) :)

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Voice is for CBers, amateur radio operators, the average citizen, and the military. In other words, voice is for everyone with a mouth. CW is for those who choose this newer mode of communication. Newer? Why yes. Voice has been around for a million years.


Thu Nov 08, 2012 3:55 pm
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