Homebrew 1:1 Balun

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JohnnyLarge
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Homebrew 1:1 Balun

Post by JohnnyLarge »

After making my own dipole, I decided to have a go at making a Balun following the instructions here.
http://1.bp.blogspot.com/-Ow6CTxZwYpE/U ... 00/1-1.png

I'm no electronics engineer but looking at the circuit, I read a dead short?

Anyway, I decided to make one and got the bits for about a fiver. I came up with this.
Image

I'm a bit reluctant to put it below my antenna in case I fry my Yaesu. Would someone with a more experienced eye cast their eye over it and tell me if it looks right with the diagram I've used? I've tried to be as accurate as possible and even wound the wires in the position in the diagram.
It's a bit over engineered I suppose but hopefully it will do the job.

Cheers
John :geek:
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cjay
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Re: Homebrew 1:1 Balun

Post by cjay »

JohnnyLarge wrote:After making my own dipole, I decided to have a go at making a Balun following the instructions here.
http://1.bp.blogspot.com/-Ow6CTxZwYpE/U ... 00/1-1.png

I'm no electronics engineer but looking at the circuit, I read a dead short?

Anyway, I decided to make one and got the bits for about a fiver. I came up with this.
Image

I'm a bit reluctant to put it below my antenna in case I fry my Yaesu. Would someone with a more experienced eye cast their eye over it and tell me if it looks right with the diagram I've used? I've tried to be as accurate as possible and even wound the wires in the position in the diagram.
It's a bit over engineered I suppose but hopefully it will do the job.

Cheers
John :geek:
Dead short to DC but nothing like at the frequencies you'll be using and there is nothing wrong with over engineering a piece of kit, it saves you having to climb about repairing it every ten minutes
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bigpimp347
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Re: Homebrew 1:1 Balun

Post by bigpimp347 »

this is what a lot of people don't understand..
electrical DC and electrical RF are two different things..
a magnetic loop can use a 9" bit of wire shorted inner to outer with a larger loop around it..
but try to explain it's a DC short and not an RF short and people are stumped..
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JohnnyLarge
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Re: Homebrew 1:1 Balun

Post by JohnnyLarge »

I've bunged it inline and the result is....................SWR over 3 from 1:1 and no perceived signal.
Bugger, I'll check it out again.
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JohnnyLarge
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Re: Homebrew 1:1 Balun

Post by JohnnyLarge »

Lol.
Just checked and found the problem. I've mounted the SO239 incorrectly and not left enough 'neck' for the PL259 to grip to so the connection is not 100%. Two wire to desolder, remount the SO239, resolder and we're good to go.
God, I'm crap!
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Re: Homebrew 1:1 Balun

Post by Mattylad »

JohnnyLarge wrote:God, I'm crap!
No, your experimenting and making your own kit & learning.

That's not crap, that's to be applauded.

I like the box it's in & the build - looks good & I hope it works well.
2E1IIP

Re: Homebrew 1:1 Balun

Post by 2E1IIP »

Nice job fella - spot the 2mm Black/White automotive cable :)
JohnnyLarge
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Re: Homebrew 1:1 Balun

Post by JohnnyLarge »

Still not right though. When I connect the pl259's up nice and snug at both ends, I get no signal.
Undo the sleeve and pull the plug out slightly at the radio end so the earth isn't in place and the signal returns.
Must be a wire in the wrong place and it can only be one of two. The location of the green wire connections in the circuit diagram are a bit puzzling.
Mmmmmmmmm.

Thanks for the positive comments so far.
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JohnnyLarge
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Re: Homebrew 1:1 Balun

Post by JohnnyLarge »

Cracked it!
The middle wire coming off the toroid needed to go to the earth lug on the SO239 and prior to the wind and not to the negative after the wind.

Yep - Sounds complicated to me too but I figured it out and it works.
Whether it will actually improve my station, I'm not 100% sure but for a fiver it's got to be worth a go.
SWR is 1:5, so a little alteration on length on the antenna and it will be sorted.
:clap:
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andymuza
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Re: Homebrew 1:1 Balun

Post by andymuza »

Job well done.
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Re: Homebrew 1:1 Balun

Post by ROTEL240 »

Nice job John and very well made you will have to let us if you have made any improvements and thanks for the qso the other day.
JohnnyLarge
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Re: Homebrew 1:1 Balun

Post by JohnnyLarge »

No problem, Cheers!
Sorry I disappeared but dinner was ready and there was a bit of a circle going on there.
Hopefully I'll hear you again but the PLT/QRM is killing me at home. Hopefully i'll get out one day soon and give the new radio a work out.
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