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TV 4:1 BALUN
I was considering using a TV type 4:1 balun on 2 meters. Does anyone
know how much power these can handle? I remember a guy doing this when I was a teenager(long ago) but I think the baluns were built a little stouter back then than they are now. Jimmie |
TV 4:1 BALUN
On Sat, 17 Jan 2009 12:44:05 -0800 (PST), JIMMIE
wrote: I was considering using a TV type 4:1 balun on 2 meters. Does anyone know how much power these can handle? I remember a guy doing this when I was a teenager(long ago) but I think the baluns were built a little stouter back then than they are now. Hi Jimmie, Have your tried researching the archives for this topic? Google's search tools can easily provide those answers. What do you have that is 1. a 200 Ohm load, or 2. a 12.5 Ohm load? Is it balanced, or unbalanced? Does this BalUn have a pedigree (like Radio Shack's "Best TV") or could it actually be an FM BalUn? If it is a TV BalUn, which band? How much power are you going to apply to the load? 73's Richard Clark, KB7QHC |
TV 4:1 BALUN
On Jan 17, 2:44*pm, JIMMIE wrote:
I was considering using a TV type 4:1 balun on 2 meters. Does anyone know how much power these can handle? I remember a guy doing this when I was a teenager(long ago) but I think the baluns were built a little stouter back then than they are now. Jimmie I wouldn't bother with those.. Tiny gauge wire.. Might be usable for a receive antenna, but I sure as heck wouldn't use one for transmit. I bet they are fairly lossy. Also.. they may not work too well on the HF frequencies being they are designed for VHF/UHF. |
TV 4:1 BALUN
On Jan 17, 4:59*pm, Richard Clark wrote:
On Sat, 17 Jan 2009 12:44:05 -0800 (PST), JIMMIE wrote: I was considering using a TV type 4:1 balun on 2 meters. Does anyone know how much power these can handle? I remember a guy doing this when I was a teenager(long ago) but I think the baluns were built a little stouter back then than they are now. Hi Jimmie, Have your tried researching the archives for this topic? *Google's search tools can easily provide those answers. What do you have that is 1. a 200 Ohm load, or 2. a 12.5 Ohm load? Is it balanced, or unbalanced? Does this BalUn have a pedigree (like Radio Shack's "Best TV") or could it actually be an FM BalUn? If it is a TV BalUn, which band? How much power are you going to apply to the load? 73's Richard Clark, KB7QHC Googling TV BalUn was useless but searching fot 2M Balun proved more useful. Per an article by K3MT they should be able to handle power in the 5 to 10 watt range. More than enough for my purpose. I cracked open a couple and foundd that tthe type that go frm screw connectors to male F connector have a larger transformer than the barrel type. This was at least true for the couple that I sacrificed to the radio gods. K3MT"s data was on the barrrel or tubular type. Jimmie |
TV 4:1 BALUN
On Sun, 18 Jan 2009 00:52:28 -0800 (PST), JIMMIE
wrote: Googling TV BalUn was useless but searching fot 2M Balun proved more useful. Per an article by K3MT they should be able to handle power in the 5 to 10 watt range. More than enough for my purpose. I cracked open a couple and foundd that tthe type that go frm screw connectors to male F connector have a larger transformer than the barrel type. This was at least true for the couple that I sacrificed to the radio gods. K3MT"s data was on the barrrel or tubular type. Jimmie Hi Jimmie, So, going further with this resource you found, was there any report of how "well" it worked? Merely surviving the application of 5 to 10 Watts isn't exactly proof of suitability for performance. Even a SWR report could mask the fact that a BalUn inappropriately applied is operating as a padding resistor. Going further yet, was it reported what style of BalUn it was? Guanella? Ruthroff? Not all BalUns perform equally, and for reception (the class of BalUn you are mining for transmission application) it is arguable that it matters. Lastly to your first statement Googling TV BalUn was useless but searching fot 2M Balun proved more useful. The distinction was useful, but were you Googling the Web, or this group? 73's Richard Clark, KB7QHC |
TV 4:1 BALUN
On Jan 18, 1:19*pm, Richard Clark wrote:
On Sun, 18 Jan 2009 00:52:28 -0800 (PST), JIMMIE wrote: Googling TV BalUn was useless but searching fot 2M Balun proved more useful. Per an article by K3MT they should be able to handle power in the 5 to 10 watt range. More than enough for my purpose. I cracked open a couple and foundd that tthe type that go *frm screw connectors to male F connector have a larger transformer than the barrel type. This was at least true for the couple that I sacrificed to the radio gods. K3MT"s data was on the barrrel or tubular type. Jimmie Hi Jimmie, So, going further with this resource you found, was there any report of how "well" it worked? *Merely surviving the application of 5 to 10 Watts isn't exactly proof of suitability for performance. *Even a SWR report could mask the fact that a BalUn inappropriately applied is operating as a padding resistor. Going further yet, was it reported what style of BalUn it was? Guanella? *Ruthroff? *Not all BalUns perform equally, and for reception (the class of BalUn you are mining for transmission application) it is arguable that it matters. Lastly to your first statementGoogling TV BalUn was useless but searching fot 2M Balun proved more useful. The distinction was useful, but were you Googling the Web, or this group? 73's Richard Clark, KB7QHC K3MT had used them in 2M project so for the time being I will let it go at that for now. Iam concerned about the cores saturating at that power level but I doubt if there is a lot of info on it. When I get off the road in a couple of weeks I will try hooking a couple of them back to back to a dummy load, putting 10 watts in and seeing what happens. The web. Jimmie |
TV 4:1 BALUN
"Richard Clark" wrote in message ... On Sun, 18 Jan 2009 00:52:28 -0800 (PST), JIMMIE wrote: Googling TV BalUn was useless but searching fot 2M Balun proved more useful. Per an article by K3MT they should be able to handle power in the 5 to 10 watt range. More than enough for my purpose. I cracked open a couple and foundd that tthe type that go frm screw connectors to male F connector have a larger transformer than the barrel type. This was at least true for the couple that I sacrificed to the radio gods. K3MT"s data was on the barrrel or tubular type. Jimmie Hi Jimmie, So, going further with this resource you found, was there any report of how "well" it worked? Merely surviving the application of 5 to 10 Watts isn't exactly proof of suitability for performance. Even a SWR report could mask the fact that a BalUn inappropriately applied is operating as a padding resistor. Going further yet, was it reported what style of BalUn it was? Guanella? Ruthroff? Not all BalUns perform equally, and for reception (the class of BalUn you are mining for transmission application) it is arguable that it matters. Lastly to your first statement Googling TV BalUn was useless but searching fot 2M Balun proved more useful. The distinction was useful, but were you Googling the Web, or this group? 73's Richard Clark, KB7QHC Hi Richard I made some insertion loss measurements on some of the low cost TV (4:1) baluns when I was trying to understand that 137 MHz antenna. I didnt save any data. I did use several types of baluns. They were all typically the Radio Shack quality. At 137 MHz, the insertion loss was about 2.5 dB for two baluns connected in series, back to back. I know that seems high, but the units are really not well built. It seems that the original poster, Jimmie, might consider using RFI ferrites around the coax instead of the TV 4:1 baluns. My measured data indicates the low cost ferrites, intended to be used to minimize RFI conduction on the outside of cables, work quite well at 144 MHz. Jerry |
TV 4:1 BALUN
On Sun, 18 Jan 2009 12:35:01 -0800 (PST), JIMMIE
wrote: K3MT had used them in 2M project so for the time being I will let it go at that for now. Iam concerned about the cores saturating at that power level but I doubt if there is a lot of info on it. When I get off the road in a couple of weeks I will try hooking a couple of them back to back to a dummy load, putting 10 watts in and seeing what happens. The web. Jimmie Hi Jimmie, Last things first, you should Google in "Groups," specifically this group. This isn't a guarantee, but at least you will land in a thread where discussion will reveal flaws where they exist. For a core to saturate reveals a misunderstanding of how the BalUn works (it goes to the same correspondents who speak of "turns ratio"). The most effective BalUn provides a high common mode reactance or resistance to current. Hence current in that mode will be low. With low current into a high resistance you have low power dissipation. Core saturation never becomes a problem, and is a distinctly separate issue - although solved through the same mechanism. The most effective BalUn adds absolutely no differential mode reactance or resistance. Again, where there is high current and no resistance, there is no power dissipation and zero core saturation (for the same reasons, but through different mechanisms). Practical BalUns have some residual reactances and resistances that they add to the transmission circuit. A Ruthroff BalUn design even purposely introduces this to its own limitation (and no advantage over other designs). The Ruthroff design invites core saturation. A Guanella BalUn seeks to be the most effective design to its advantage over the Ruthroff. The Guanella design suppresses core saturation. There are limitations, of course. You can still flame out a Guanella if the core reactance/resistance is under designed, or your load is unbalanced and not suited to the transformation ratio. This can be aided through choking the input to the BalUn (which serves as a choke, too, for controlled loads). The back-to-back test is useful. Take one BalUn between a finger and thumb and count to 10. If you don't raise a welt, then they probably are not too lossy. 73's Richard Clark, KB7QHC |
TV 4:1 BALUN
On Sat, 17 Jan 2009 12:44:05 -0800 (PST), JIMMIE
wrote: I was considering using a TV type 4:1 balun on 2 meters. Does anyone know how much power these can handle? I remember a guy doing this when I was a teenager(long ago) but I think the baluns were built a little stouter back then than they are now. May I suggest using a coaxial cable 4:1 balun instead of ferrite core type. A 1/2 wave electrical length of coax cable, some soldering, and you're done. For just 2 meters, the bandwidth is just fine and the loss is no more than that of the coax cable. For low power, small diameter RG-174 type coax is fine. I use 4:1 coax baluns for matching 300 ohm folded dipole antennas: http://users.belgacom.net/hamradio/schemas/14balun.gif The common TV balun has two xfomers inside, which are sometimes combined on a single core. See schematics at: http://members.tripod.com/rclindia/trans.html http://www.electronics-tutorials.com/basics/baluns.htm However, if size is an issue, I guess the coax balun is a bit large. For just 2 meters, the ferrite core is not necessary. Just find a block of PTFE (Teflon) or plastic, and drill it to resemble the TV balun core, use 2 PTFE toroid cores (if you can find them), or simulate a torroid with a stack of nylon washers. Then wind the 2 pairs of 2 wires through the holes and bring out the connections. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
TV 4:1 BALUN
On Jan 18, 10:32*pm, Jeff Liebermann wrote:
On Sat, 17 Jan 2009 12:44:05 -0800 (PST), JIMMIE wrote: I was considering using a TV type 4:1 balun on 2 meters. Does anyone know how much power these can handle? I remember a guy doing this when I was a teenager(long ago) but I think the baluns were built a little stouter back then than they are now. May I suggest using a coaxial cable 4:1 balun instead of ferrite core type. *A 1/2 wave electrical length of coax cable, some soldering, and you're done. *For just 2 meters, the bandwidth is just fine and the loss is no more than that of the coax cable. *For low power, small diameter RG-174 type coax is fine. *I use 4:1 coax baluns for matching 300 ohm folded dipole antennas: http://users.belgacom.net/hamradio/schemas/14balun.gif The common TV balun has two xfomers inside, which are sometimes combined on a single core. *See schematics at: http://members.tripod.com/rclindia/trans.html http://www.electronics-tutorials.com/basics/baluns.htm However, if size is an issue, I guess the coax balun is a bit large. For just 2 meters, the ferrite core is not necessary. *Just find a block of PTFE (Teflon) or plastic, and drill it to resemble the TV balun core, use 2 PTFE toroid cores (if you can find them), or simulate a torroid with a stack of nylon washers. *Then wind the 2 pairs of 2 wires through the holes and bring out the connections. -- Jeff Liebermann * * 150 Felker St #D * *http://www.LearnByDestroying.com Santa Cruz CA 95060http://802.11junk.com Skype: JeffLiebermann * * AE6KS * *831-336-2558 I was rummaging through my mobil junk er toolbox and came across an old package of air core TV baluns. These date back to the day when TVs were usually fed with twin lead. Tuesday I may be able to get to some test equipment to check out the losses on those. Gee getting to spend a 3day weekend on the road is such fun. Jimmie |
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