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Author Topic: Balun for A3S  (Read 1303 times)
GM4CUX
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Posts: 9




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« on: July 13, 2013, 11:26:29 AM »

I have a A3S HF beam. They recommend a co-ax wound balun and I don't fancy that at all!
I would rather have a solid contained balun.
The question is : If feeding the A3S with 50 Ohm coax do I require a 1;1 balun or 4:1 balun?
Information appreciated, thank you.
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AA4PB
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Posts: 12892




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« Reply #1 on: July 13, 2013, 11:44:38 AM »

A 1:1 balun. I've used the prescribed coax balun on the A3 and the TA33 with no issues. Just tape up the turns with plastic electrical tape and add several coats of plastic spray. The one on the TA33 has been up and working for 20+ years now.
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KB4OIF
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Posts: 73




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« Reply #2 on: July 13, 2013, 11:51:51 AM »

AA4PB.  I will be putting up a TA 33 Jr WARC in the near future.  How far down the coax should it (coax ail wound Balun) and is there specific amount of turns and a specific size of the circle.  Been looking for this info for a while.

KB4OIF
John
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WA8UEG
Member

Posts: 361




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« Reply #3 on: July 13, 2013, 12:18:45 PM »

6 turns with a diameter of 4 to 6" will work. You can mount it on the boom prior to where the mast connects. Ideal would be 6 turns 4" in diameter laid flat against each other not bunched but bunched will work fine on the frequencies the TA33 works.
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KB4OIF
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Posts: 73




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« Reply #4 on: July 13, 2013, 12:26:35 PM »

Thanks!!!!!   
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K7KBN
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Posts: 2813




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« Reply #5 on: July 13, 2013, 12:42:47 PM »

4" diameter might be fine for RG-58, but it's way too tight for any of the 0.405" coaces.  8" would be better for those.
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73
Pat K7KBN
CWO4 USNR Ret.
W5WSS
Member

Posts: 1744




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« Reply #6 on: July 13, 2013, 01:56:55 PM »

I would use a 1:1 current balun strongly fastened/bonded to the boom though I would also use a barrel splice and exacting make of coaxial feedline pigtail onwards to the feed point terminals. Bond the outer shell of the barrel (common to the shielding of the feedline) located just before the balun and the balun is located adjacent to the feed point to the antenna boom using a mechanical fastener designed/saddle for the purpose of fastening and bonding.

I would make very sure that the connections of the barrel is weather proofed for added assurance and longevity.
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WB2WIK
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Posts: 20611




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« Reply #7 on: July 13, 2013, 02:23:04 PM »

I agree the "coaxial choke" current balun wound of coax can work okay 14-30 MHz.  The problem is if the beam also covers 30m or 40m as some do; then, that choke balun becomes much more of a challenge and ferrites help a lot.

A good 1:1 ferrite balun to the rescue. Wink
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K3GM
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Posts: 1815




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« Reply #8 on: July 14, 2013, 05:41:00 PM »

I used both the coil of coax and a 1:1 balun and thought the latter gave better results.
I used a DX Enginering box balun and mounted it like so:
http://i9.photobucket.com/albums/a96/TwoSevenRight/DSCN1144.jpg
http://i9.photobucket.com/albums/a96/TwoSevenRight/DSCN1143.jpg
Note that the wire from the balun the the element was figured into the overall element length.
« Last Edit: July 14, 2013, 05:47:53 PM by K3GM » Logged
MM0WAX
Member

Posts: 1




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« Reply #9 on: July 18, 2013, 01:36:18 PM »

Hi Graham, on my Mosley TA63 M I use the following choke, as recommended by GM3SEK, see here http://www.ifwtech.co.uk/g3sek/in-prac/ The particular choke I use is the figure of 8 in bottom right of picture. Works ok on the 6 bands that the Mosley covers.

Brian
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