RolandSWL
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« on: July 25, 2012, 11:40:14 AM » |
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Hi All,
I'm trying to understand the importance of balun placement within the antenna system. I have heard that it's OK to place it near the tuner (if used) or at the antenna feed point.
What difference does it make where it's placed? For simplicity, let's say it's a 1:1 and is only for the purpose of keeping the coax feedline from radiating r.f.
Thanks, Roland............
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WA1GFZ
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« Reply #1 on: July 25, 2012, 02:41:13 PM » |
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Search on "ON9CVD" Bob has some great balun atricles on his web site
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W4NEQ
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« Reply #2 on: July 25, 2012, 06:39:15 PM » |
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The most common correct use is placing a 1:1 balun at the center of the (BALanced) dipole fed with (UNbalanced) coaxial cable. Not essential, but can be a good idea.
Chris
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The Slab Bacon
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« Reply #4 on: July 30, 2012, 09:31:08 AM » |
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After many many years of HIGH-power AM, high mod percentages, and long winded transmissions into a bad load, here it is!  |
"No is not an answer and failure is not an option!"
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W4NEQ
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« Reply #5 on: July 30, 2012, 10:35:33 AM » |
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I'm curious why you chose iron powder cores instead, of say 61 ferrite? Were you concerned about possible saturation? I don't think there's much common mode current.
Chris
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The Slab Bacon
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« Reply #6 on: July 31, 2012, 08:30:55 AM » |
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I'm curious why you chose iron powder cores instead, of say 61 ferrite? Were you concerned about possible saturation? I don't think there's much common mode current.
Chris
$.50 each at a hamfest. After a heated discussion on the air with another well-known AMer who was very adamant that "baluns dont work", "you can't build a balun that will take that kind of use" (and I just launched another store-bought balun up in flames) I just felt obligated to prove him wrong. That being said, I wasn't going to spend a lot of money for cores just for an experiment. That one swept very well from 1.5 to 15 Mhz. So............. If it covered 160, 80, and 40, that was all that I was looking for. I have been using it for well over 10 years now with no problems. (If it ain't broke, don't fix it) We (this forum) have had this discussion far too many times, so I'm just going to leave it at that.......................... |
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"No is not an answer and failure is not an option!"
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N4LTA
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« Reply #7 on: July 31, 2012, 09:04:33 AM » |
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Best example proving indeed that baluns do work is the receiving balun designed by Clifton labs.
I have an active LF antenna about 300 feet from my house at the edge of a lake and it is at least 300 feet from any house or power line. I have a multicoil balun at the antenna and a good ground and another balun at the point the coax enters radio room and another good ground. When I first tested it, I thought something was wrong because of the dramatic reduction in noise. At my QTH, most of the LF noise and VLF noise is generated in the house and picked up as common mode on the coax shield. The two baluns eliminate most of it.
Pat
N4LTA
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K3ZS
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« Reply #8 on: July 31, 2012, 12:54:09 PM » |
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We (this forum) have had this discussion far too many times, so I'm just going to leave it at that.......................... [/quote] I learned also that talking about baluns is about the same as making a political comment on the QSO board. |
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ke7trp
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« Reply #9 on: July 31, 2012, 02:40:10 PM » |
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Frank. Does that BIGUN get warm or hot? Looks like its built tough!
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WA1GFZ
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« Reply #10 on: July 31, 2012, 03:02:55 PM » |
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-2 iron is more stable than type 61. You will need more cores stacked or more turns to reach minimum inductance. I had one on the input of my fugly tuner with 6 cores (-2) that got slightly warm at QRO but never any danger. Amadon has some BB transformer apps on the web.
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The Slab Bacon
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« Reply #11 on: July 31, 2012, 03:23:55 PM » |
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Frank. Does that BIGUN get warm or hot? Looks like its built tough!
Never! Lots of core is your friend   |
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"No is not an answer and failure is not an option!"
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ke7trp
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« Reply #12 on: July 31, 2012, 05:13:44 PM » |
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What gauge wire is that? Teflon? I might build one of those. Looks like it would take some serious fire in da wire.
C
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W4AMV
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« Reply #13 on: July 31, 2012, 05:28:04 PM » |
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I'm curious why you chose iron powder cores instead, of say 61 ferrite? Were you concerned about possible saturation? I don't think there's much common mode current.
Chris
61 Material has a perm of 125 and its good to 25 or so MHz. At 40 MHz the Q is unity and the 61 material is lossy. Its going to get HOT. If you can come up with enough L per unit turn and the frequency is low, then powered iron, lower perm, will have lower loss and less heat. Even below 25 MHz, if the power is high enough the ferrite runs the risk of heating UNLESS there is no current on the coax outter shield. If you build a coaxial transformer and break the shielded connection (say in building a 4:1) and pass that portion of the coax back through ferrite... watch out... it will get HOT at high power. |
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KB2WIG
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« Reply #14 on: July 31, 2012, 05:29:25 PM » |
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" I learned also that talking about baluns is about the same as making a political comment on the QSO board. " How 'boute 'Can one use a balun on their G5RV  ' klc |
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What? Me worry?
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The Slab Bacon
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« Reply #15 on: August 01, 2012, 09:55:10 AM » |
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What gauge wire is that? Teflon? I might build one of those. Looks like it would take some serious fire in da wire.
C
I wanted to use #10 or 12 silver teflon (I knew I had some SOMEWHERE)  After tearing the basement apart 4 times, I gave up, just couldn't find it no matter where I looked   So I ended up finding some #16 silver teflon. Way too small, so I trippled it up for the experiment. It ended up working so well that I just left it that way. That was at least 10-12 (or more) years ago. As far as the losses over 25Mhz I flat out didn't give a damn! I didn't plan to use it over 40m. When I swept it, I found that it was perfect all the way to 15Mhz, so I was happy as the proverbial clam!! |
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"No is not an answer and failure is not an option!"
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WA1GFZ
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« Reply #16 on: August 02, 2012, 12:31:46 PM » |
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I do transmission line transformers with type 61 that work well to 100MHz. All this is easy until you dump some DC current through the core along with RF.
Frank I ran quadfilar #14 in my transformer I think it was 4 or 5 turns on 6 cores. Ran cool at 1500 watts. It was 1:2 step up into my fugly tuner.
-2 iron you need about 2.5X the turns or wire or coax as type 61.
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