Posted: 2/3/2008 1:55:01 PM EDT
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OK, I have a form in my hand from LDG that says I can have a free 1:1, or 4:1 bulan. I have read ar-jedi's post on what a bulan is.... My question. I still don't 100% understand the differnce between the two. Is a 1:1 used for just single band, and 4:1 used for multi band operation? ( Am I way off in my understanding?) If I were going to build a loop antenna would I use a 4:1?, or a fan dipole? I guess to make the question simple, What types of antenna's/situation's would I use a 1:1 for, or a 4:1 bulan for? Im trying to figure out what one to order based on my future attempts at antenna building.  Thanks. |
free is a good deal on a balun, btw. the LDG 1:1 is evidently a good unit. the LDG 4:1 has taken some slagging over on Eham (link)
one is a 1:1, the other is a 4:1.  one has constant impedance through it, the other provides a 4x impedance conversion.
no.
yes.
it depends on the feedpoint impedance of the antenna, the type of feedline (coax or ladder), and the output mode (balanced or unbalanced) of your amplifier.
it depends. see above.
suppose you have a balanced fed antenna, such as a dipole, and you want to feed it from a transceiver with an unbalanced output (e.g., most HF rigs) over a run of RG8 coax. the antenna impedance is roughly 50 ohms, the coax is 50 ohms, the transmitter output is 50 ohms -- so you don't need any impedance conversion, you just need the balun function. hence, you pick a 1:1 balun -- 50 in/50 out. you run coax from the rig to the centerpoint of the antenna, and put the 1:1 balun there. in this example, the primary purpose of the the balun is to prevent RF current from coming back down the shield of the coax, and potentially causing issues inside the shack. suppose you have a balanced fed antenna, such as a off-center-fed multi-band dipole, and you want to feed it using ladder line. why ladder line? it is less lossy than coax, and lighter than coax, and so on. the ladder line has a 450 ohm impedance. using a 4:1 balun, it's possible to mate the 50 ohm unbalanced output of your HF rig to the ladder line. look for some example uses of 1:1 and 4:1 baluns on the web -- you'll get lots of ideas. which should you take free? *i* could see more use for the 4:1 balun as it would allow your autotuner a better shot at matching "awkward" feedpoint impedance antennas. on the other hand, *i* could also see a case where a 1:1 balun would be useful for properly driving a single band (cut) dipole without RF leaking abck into the shack. get some input from the rest of the HR forum crowd, and also do some googling. hth, ar-jedi |
 I found This. and I think it helps with what I was looking for.... I can see that I was only getting about 25% of what a balun was... I just figured it was for connecting twin lead, or ladder line to coax, and trying to balance them out... looks to be a little more than just that.
Im thinking I should just get both!..
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where is that "Truckload of FAIL" jpeg when i need it...  ar-jedi |
R-32 is a FAIL at the internet, but try clicking this anyway...
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that is an excellent tech article. ar-jedi |
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Most antenna tuners that are built for use with balanced feedline, contain a 4:1 balun. The main use for an external 4:1 balun (that I can think of) would be if you are using a balanced antenna with an antenna tuner that doesn't have an internal balun. "I just figured it was for connecting twin lead, or ladder line to coax, and trying to balance them out... looks to be a little more than just that." The antenna is BALanced. Coax feedline is UNbalanced. So you use a BALUN to feed a BALanced antenna with UNbalanced feedline; BALanced to UNbalanced, thus the name BALUN. Your rig wants to be fed with an approx. 50 ohm UNbalanced load. So, if you are feeding a balanced antenna with a balanced feedline (such as ladderline, open wire feeder, TV Twinlead...), you need to use a balun at the rig to go from BALanced feedline to the unbalanced output of your rig. OK, so let's say you have a 130 foot dipole, fed with ladderline and you are going to use this antenna on all bands with an antenna tuner, This presents a weird impedance far from what your rig wants to see in addition to the fact that that the antenna/feedline is balanced and your rig wants to see an unbalanced load. So, you feed the ladderline into balun and antenna tuner, You tune the impedance from whatever it was to the 50 ohms that your rig wants and at the same time, make it unbalanced. But what if the impedance of the load (antenna/feedline) is so weird that the tuner can't tune it to 50 ohms ? So you wind the balun to also be a transformer. That is where the 4:1 balun comes into play. It converts the impedance by 4:1. If the impedance was balanced and 4000 ohms, the 4:1 balun would make it unbalanced at 1000 ohms. Something easier for your tuner to handle. Think about coax; the signal is supposed to be traveling down the center conductor and it is shielded by the braid. There shouldn't be a signal on the braid. That is unbalanced. All the signal is on one of the conductors. If you have some of the current on the shield it isn't a shield. Instead of shielding the signal, it is going to radiate the signal. We don't want that. We want it all kept inside so it all gets to the antenna, and so it doesn't cause interference. So we use a balun. To actually answer your question, I would definitely get the 4:1. |