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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c
As per title looking for a Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms coaxial unbalanced. Capable of full legal power.

Buy a complete one or Kit or the information on how to build


Many thanks

Anthony

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Tue Nov 13, 2012 10:25 pm
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
Take a look at the cobweb balun on my web site:
http://www.karinya.net/g3txq/cobweb/

PS: Should have asked first: what frequency range?

73,
Steve G3TXQ


Tue Nov 13, 2012 10:41 pm
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
OOps new I forget something. 40mts.

Thanks for link will have a look.

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Tue Nov 13, 2012 11:06 pm
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
Looks exactly what I am after thanks, just need a UK source for the FT140-61 Ferrite Toroids,

Am I right in thinking using this would mean I only need one piece around each toriod?
http://www.ebay.co.uk/itm/RG316-25-Ohm- ... 1002045128

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Tue Nov 13, 2012 11:29 pm
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
The FT140-61 is available here:
http://www.amtoolsuk.com/joomla/index.p ... itstart=20

However - my balun was optimised for 20m thru 10m use on the Cobweb; for 40m use a different core material than #61 might be better and/or more turns. I'll try to take some measurements today and check how well it does at the lower frequency.

Yes, 25 Ohm coax means you only need the one winding on each core - good find! Pity it's not a bit cheaper :) I'm slightly concerned that the thicker centre conductor might make it difficult to wind on the "140" size cores, but if that's the case the "240" size are readily available.

73,
Steve G3TXQ


Wed Nov 14, 2012 8:44 am
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
Just checked one of my baluns - two parallel RG316(50) on each FT140-61 core - and it looks fine on 40m.

Looking through my past eBay purchases I see I bought some of that 25 Ohm coax from the Enigma shop. I can only have bought it with a view to trying it on the 1:4 balun, but can't for the life of me remember if it was OK :scratch:

73,
Steve G3TXQ


Wed Nov 14, 2012 9:27 am
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
Yor are right its a little expensive, so I think I will go with your option, one question would this be suitable for High power(legal limit), unlikely I will run it that but do have the capability so would like to make sure the balun can handle it.

Many thanks for all the help.

Anthony

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Wed Nov 21, 2012 4:09 pm
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
RG316 is rated at 1.3kW at 7MHz. Because there are four lengths of coax on the balun, each taking an equal share of the cable losses, the limit would be 5.2kW if working into a matched load. You can de-rate that by whatever the SWR is.

In practice the core size would be a limitation before the RG316.

73,
Steve G3TXQ


Wed Nov 21, 2012 5:54 pm
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
I had to buy a Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms coaxial unbalanced from USA it is 5Kw limit I used it to add 40m band to Steve's hexbeam and it works great no interaction info on link below.I tried to get one from eu & uk but nothing,it took about 2 weeks to deliver and has to pay 11 pounds tax duty also.



http://www.cwsbytemark.com/index.php?ma ... th=206_213


40m Hexbeam Link

http://members.home.nl/pc4u/hex.pdf

73's

Steve


Mon Nov 26, 2012 12:14 am
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
Steve
Thanks for the information, I did find those baluns when I searched, but decided I would build due to there cost with postage and duty. I guessing from your description that having the large metal case balun mounted on the centre pole doesnt affect the antennas performance.
What did you form your traps on , I havent been able to easily find 42mm plastic pipe? Did you need to alter the wire lengths at all or was it exactly as per the instructions?

I now have all the parts so just need the time and weather to allow me to try it, but any information you can provide most greatfull received.

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Mon Nov 26, 2012 8:52 am
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
Leaving myself open to ridicule with possibly a silly suggestion :blush: ......... but can you not take care of the mismatch using this method, it'll take a fairly long length of coax which perhaps wound up would also act as a good choke.
http://www.qsl.net/dk7zb/dk7zb-match.htm

"With 2x50-Ohm-cables 12.5 to 50 Ohm."

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Mon Nov 26, 2012 10:48 am
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
That appears fine for a monoband solution; but I'm not sure how effective a choke it would make.

Steve G3TXQ


Mon Nov 26, 2012 11:10 am
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 Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 ohms c 
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Post Re: Wanted Step Down 4:1 Balun - 12.5 ohms balanced to 50 oh
I used plastic waste pipe that you get from a plumbing shop or even homebase very cheap when making coil I needed another set of hands to create the coil bought the 1.5mm enambled wire from wires.co.uk

Due to the fact that you are making 4 coils I ordered plenty and once made ran seperate coax from the shack and mounted the !:4 Balun opposite side at the top to the 20m termination points of original hexbeam. This tuned first time and is quiet with no reaction in swr reading with hex antenna.It has its advantage over fixed dipole when pointing opposite direction but here at qth dipole is North and South and the 40m addon is a good S point down on the dipole but that is understandable.Lets just say it gives you another option when working some DX.

Hope this info helps

Cheers

Steve

MM0SAJ


Thu Nov 29, 2012 12:21 pm
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