Re: [Elecraft] OT: balun rating exceeded
Brett, There ARE kilowatt baluns, but the balun probably will not help a G5RV due to the fact it is resonant on 20 as a gain antenna, and somewhat of a mismatch on any other band. In fact, you would be better off running open wire line all the way to a Tee tuner, then using a ferrite bead 1:1 balun after the tuner and before the balanced line, ONLY if you have any RF on the tuner or rig chassis. From what you say, in your case, location has worked to mitigate imbalance and you do not need a balun if you do not see stray RF effects. Look to suppliers such as for high power balun kits if ever you need one. A balun is not very lossy to your signal, UNLESS it gets saturated. A bead balun on coax should only be handling minimal power from stray pickup to outer of the coax shield, and thus will not be saturating, to the extent other baluns might. However, G5RV and others analyzing his antenna have remarked that the balun at junction of parallel line and any coax to shack may show no benefit from a balun. Originally, the G5RV was done without a balun. It theoretically "looks" like it would be necessary, but even the venerable balanced line end fed Zepp only shows 10 per cent imbalance when end fed, per L. B. Cebik's analysis. (see www.cebik.com for extensive antenna info.) If the balun materials are big enough, they are not lossy to a significant degree, when appropriately applied to specific impedance transformation as well as balancing. Loss in a balun can be noted by seeing if it heats up. No heating from ambient to full power says there is no loss at the balun. In some applications, critical lengths of line can place the balun in a point of too high SWR, but proper design puts the balun at an appropriate point. Stuart K5KVH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] OT: balun rating exceeded
On Tue, 15 May 2007 09:35:03 -0700, Ron D'Eau Claire wrote: >The bottom line is that modern baluns are NOT designed to be used in systems >with a wide range of impedances. I suggest that those interested in this thread study my tutorial on RFI and ferrites. It includes a long section on choke baluns. http://audiosystemsgroup.com/RFI-Ham.pdf I am currently working on updating the "cookbook" section with improved specific recommendations about how coaxial choke baluns must be wound to minimize stray capacitance. I've done enough work on this to have a good handle on what works and what doesn't, but had to interrupt it for a biz trip to Europe. Until I've finished that and posted it, I'll simply say that the coax should be closely spaced ONLY where it goes through the toroids, and VERY WIDELY SPACED everywhere else. The difference between a coaxial choke with close spaced turns and one with wide spaced turns is HUGE. For example, five CLOSE-spaced turns of RG8 through five #31 toroids will cause a resonance (and peak performance) in the 2-3 MHz range, while WIDE-spaced turns will yield excellent performance all the way up to 10 meters. 73, Jim Brown K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] OT: balun rating exceeded
What usually happens under those conditions may not damage the balun but does cause lots of RFI: the balun turns non-linear! When the magnetic flux saturates the core it heats and its magnetic properties change dramatically. That produces a non-linear transfer function. Non-linearity is the hallmark of a good mixer! So your balun starts making all sorts of unintentional RFI that wasn't at the output of the transmitter. Under such conditions the core is absorbing a lot of power too. Had you touched it, you'd probably have found it noticeably warm, perhaps even hot, possibly hot enough to blister your finger. At the extreme, the core will heat and crack, ruining it and the balun. But that doesn't always happen. Another temporary failure mode is arcing. That may be more obvious since you may hear it if the balun is nearby. Most baluns are not made to handle really large RF voltages. There isn't enough spacing between leads and terminals for that. The insulation on the wires isn't rated for high voltages. So, when you have it at a voltage loop and crank up the power, it's easy for an arc to occur across adjacent leads. If it's through the air between metallic conductors usually no harm is done. Often it's through the insulation of adjacent wires or across a PCB. In those cases a carbon trail is formed that will have to be removed before the balun will work properly again. The bottom line is that modern baluns are NOT designed to be used in systems with a wide range of impedances. You can get away with using a balun in a multiband doublet, Windom fed with parallel lines, G5RV, etc., only when those antennas happen to provide a reasonable impedance at the balun: neither too low (which would produce high RF currents) or too high (which would produce high RF voltages). Many years ago many of us did use baluns in such systems quite successfully. They used air core coils. Air does not saturate magnetically. They had large enough spacing to avoid arcing at high RF voltages. Such baluns commonly measured a foot square, or larger, by nearly a foot deep. They were generally mounted on the wall well away from anything that might draw an unintentional arc from the coils - such as the operator! There are times when size does matter! Ron AC7AC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Markowski Sent: Tuesday, May 15, 2007 6:08 AM To: Elecraft Subject: [Elecraft] OT: balun rating exceeded The following happened to me a few years ago as a brand new ham in my pre-Elecraft days and I wonder if anyone can explain to me the details. I apparently had high swr and exceeded the rating on my balun. It suffered accordingly but didn't completely fail. The result was when I transmitted cw on 40m an internal fuse would blow in the stereo which was on in the next room room. It took two go rounds before I caught onto the cause and effect... A new & better balun cured the problem. At the time I had a Zepp (135') and 4:1 balun at the house entrance. I assume the ruined balun was emitting all sorts of RF that the stereo amplifier picked up, tried to amplify, and couldn't. But I don't understand exactly what would make it draw that much current. Can someone enlighten me? By the way, since then I put up a dipole, halfwave for 160m, about 200' behind the house. That's what I should have begun with. Thanks! Mike ab3ap ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] OT: balun rating exceeded
Hello John: Tnx much for the reply. The G5RV is as straight as gravity will allow and the 450 ohm line is indeed perpendicular to the flattop. I use a Palomar 1500CV with it and it works well. That said, I prefer my 33 ft 40 meter vertical with 37 radials and the 40 meter loop. Jozef WB2MIC John Magliacane wrote: --- Jozef Hand-Boniakowski <[EMAIL PROTECTED]> wrote: A few years back I bought a Buxcom G5RV and running 600 watts into it, the balun that it came with was toast. I replaced it with 10 turns of coax wrapped around a Folger's coffee can. So, you replaced the balun you normally use with New Folger's Crystals. :-) Seriously though, I've given this situation a lot of thought, and I'm not thoroughly convinced an unshielded choke located in the nearfield of a radiating structure would necessarily attenuate currents flowing on the outside of the transmission line's shield. I think even a perfectly functioning, perfectly shielded balun *at the antenna feedpoint* might be somewhat moot unless the dipole is perfectly straight, and the feedline is run exactly perpendicular to the dipole (to equalize coupling to either side of the antenna). By the same token, I've often wondered just how "balanced" a balanced feedline really is under similar circumstances. Maybe twisting the line might help improve transmission line balance. Maybe using a tuner that can compensate for any voltage/current imbalance might be advantageous, as well. There are many complicating factors when it comes to antenna installation and operation. Fortunately, few, if any, turn out to be of much significance in the grand scheme of things... 73, de John, KD2BD Visit John on the Web at: http://kd2bd.ham.org/ . . . . Get the Yahoo! toolbar and be alerted to new email wherever you're surfing. http://new.toolbar.yahoo.com/toolbar/features/mail/index.php ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] OT: balun rating exceeded
--- Jozef Hand-Boniakowski <[EMAIL PROTECTED]> wrote: > A few years back I bought a Buxcom G5RV and running 600 watts into it, > the balun that it came with was toast. I replaced it with 10 turns of > coax wrapped around a Folger's coffee can. So, you replaced the balun you normally use with New Folger's Crystals. :-) Seriously though, I've given this situation a lot of thought, and I'm not thoroughly convinced an unshielded choke located in the nearfield of a radiating structure would necessarily attenuate currents flowing on the outside of the transmission line's shield. I think even a perfectly functioning, perfectly shielded balun *at the antenna feedpoint* might be somewhat moot unless the dipole is perfectly straight, and the feedline is run exactly perpendicular to the dipole (to equalize coupling to either side of the antenna). By the same token, I've often wondered just how "balanced" a balanced feedline really is under similar circumstances. Maybe twisting the line might help improve transmission line balance. Maybe using a tuner that can compensate for any voltage/current imbalance might be advantageous, as well. There are many complicating factors when it comes to antenna installation and operation. Fortunately, few, if any, turn out to be of much significance in the grand scheme of things... 73, de John, KD2BD Visit John on the Web at: http://kd2bd.ham.org/ . . . . Get the Yahoo! toolbar and be alerted to new email wherever you're surfing. http://new.toolbar.yahoo.com/toolbar/features/mail/index.php ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] OT: balun rating exceeded
It does not take much RF in the shack/house to cause problems. Keep the RF outside. An effective balun goes a long way to avoid these problems. Noise from the house couples to the antenna if there is not an effective balun, raising the receiver noise level. Using an effective balun can lower the receiver noise levels. A good balun will have negligible loss (by design). Operating Coax at high SWR (a la G5RV) can have significant loss. Even a fairly short length. Run the feedline modelling software that comes with the ARRL Antenna Books to quantify. Try to keep high SWR coax lengths to several feet at most. At least one company (DX Engineering) makes baluns that will handle high power. Take one apart and inspect it, they are well made and have a lot more ferrite than most. Operating a balun with SWR is not a problem as long as the ratings are not exceeded. The voltage and current are larger by as much as the square root of the SWR, so a 10:1 swr will increase voltage/current by as much as the square root of 10, or about 3. Use a balun with adequate voltage/current ratings for the power and SWR. A 4:1 balun current balun splits its ferrite in half for the two internal 1:1 sections. So it has half the choking reactance of a straight 1:1 for the same cost (ferrite quantity). Generally a 1:1 current balun is a better choice for high SWR use. Let the tuner do the matching, allow the balun to do the balancing. A voltage balun doesn't keep the RF out of the house, so is not of much use here. Most 4:1 baluns are voltage type, so you have to shop carefully. As to the original question about the balun failure, the ineffective balun may have allowed considerable RF onto the ground system and conducted into the stereo. The RF gets rectified and the stereo attempts to amplify the resultant frequency components within its passband (some possibly out of audio range). The high power consumption pops the fuse. Using balanced antennas and a quality effective balun keeps the RF out of the house. 73, -- Alan, wb6zqz At 06:23 AM 5/15/2007, Brett gazdzinski wrote: What is the benefit of a balun? I cant run them, as I run legal limit AM which will toast any balun I ever heard of. At 100 watts, or QRP, RF in the house cant be an issue, I don't have problems with the AM and the G5RV right over the house. I would think it would just add more loss. I used to have resonant 80 and 40 meter dipoles, but took them down and built a home made G5RV, #12 wire for the open wire line, and only about 20 feet of RG214 coax into the tuner or directly into the K2 with its built in atu. I will have very high swr on both the open wire line (does not matter as there is almost no loss), and the RG214, but there is only 20 feet of that, so I would guess the loss is slight. Now I could fit a balun if I just used the K2, but what would be the advantage? I hear you should never run a balun with any swr, the losses go way up. I think they now make tuners with the balun before the tuner (rig, balun, tuner, antenna) that works well Brett N2DTS > > The following happened to me a few years ago as a brand new ham in my > pre-Elecraft days and I wonder if anyone can explain to me > the details. I > apparently had high swr and exceeded the rating on my balun. > It suffered > accordingly but didn't completely fail. The result was when > I transmitted cw on > 40m an internal fuse would blow in the stereo which was on in > the next room > room. It took two go rounds before I caught onto the cause > and effect... A new > & better balun cured the problem. > > At the time I had a Zepp (135') and 4:1 balun at the house > entrance. I assume > the ruined balun was emitting all sorts of RF that the stereo > amplifier picked > up, tried to amplify, and couldn't. But I don't understand > exactly what would > make it draw that much current. Can someone enlighten me? > > By the way, since then I put up a dipole, halfwave for 160m, > about 200' behind > the house. That's what I should have begun with. > > Thanks! > Mike ab3ap ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] OT: balun rating exceeded
A few years back I bought a Buxcom G5RV and running 600 watts into it, the balun that it came with was toast. I replaced it with 10 turns of coax wrapped around a Folger's coffee can. Reading what G5RV had written about his antenna, he recommended that a balun not be used with his antenna. See last link at http://www.metaphoria.us/hamradio/ham_radio.htm Jozef WB2MIC Brett gazdzinski wrote: What is the benefit of a balun? I cant run them, as I run legal limit AM which will toast any balun I ever heard of. At 100 watts, or QRP, RF in the house cant be an issue, I don't have problems with the AM and the G5RV right over the house. I would think it would just add more loss. I used to have resonant 80 and 40 meter dipoles, but took them down and built a home made G5RV, #12 wire for the open wire line, and only about 20 feet of RG214 coax into the tuner or directly into the K2 with its built in atu. I will have very high swr on both the open wire line (does not matter as there is almost no loss), and the RG214, but there is only 20 feet of that, so I would guess the loss is slight. Now I could fit a balun if I just used the K2, but what would be the advantage? I hear you should never run a balun with any swr, the losses go way up. I think they now make tuners with the balun before the tuner (rig, balun, tuner, antenna) that works well Brett N2DTS The following happened to me a few years ago as a brand new ham in my pre-Elecraft days and I wonder if anyone can explain to me the details. I apparently had high swr and exceeded the rating on my balun. It suffered accordingly but didn't completely fail. The result was when I transmitted cw on 40m an internal fuse would blow in the stereo which was on in the next room room. It took two go rounds before I caught onto the cause and effect... A new & better balun cured the problem. At the time I had a Zepp (135') and 4:1 balun at the house entrance. I assume the ruined balun was emitting all sorts of RF that the stereo amplifier picked up, tried to amplify, and couldn't. But I don't understand exactly what would make it draw that much current. Can someone enlighten me? By the way, since then I put up a dipole, halfwave for 160m, about 200' behind the house. That's what I should have begun with. Thanks! Mike ab3ap ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] OT: balun rating exceeded
What is the benefit of a balun? I cant run them, as I run legal limit AM which will toast any balun I ever heard of. At 100 watts, or QRP, RF in the house cant be an issue, I don't have problems with the AM and the G5RV right over the house. I would think it would just add more loss. I used to have resonant 80 and 40 meter dipoles, but took them down and built a home made G5RV, #12 wire for the open wire line, and only about 20 feet of RG214 coax into the tuner or directly into the K2 with its built in atu. I will have very high swr on both the open wire line (does not matter as there is almost no loss), and the RG214, but there is only 20 feet of that, so I would guess the loss is slight. Now I could fit a balun if I just used the K2, but what would be the advantage? I hear you should never run a balun with any swr, the losses go way up. I think they now make tuners with the balun before the tuner (rig, balun, tuner, antenna) that works well Brett N2DTS > > The following happened to me a few years ago as a brand new ham in my > pre-Elecraft days and I wonder if anyone can explain to me > the details. I > apparently had high swr and exceeded the rating on my balun. > It suffered > accordingly but didn't completely fail. The result was when > I transmitted cw on > 40m an internal fuse would blow in the stereo which was on in > the next room > room. It took two go rounds before I caught onto the cause > and effect... A new > & better balun cured the problem. > > At the time I had a Zepp (135') and 4:1 balun at the house > entrance. I assume > the ruined balun was emitting all sorts of RF that the stereo > amplifier picked > up, tried to amplify, and couldn't. But I don't understand > exactly what would > make it draw that much current. Can someone enlighten me? > > By the way, since then I put up a dipole, halfwave for 160m, > about 200' behind > the house. That's what I should have begun with. > > Thanks! > Mike ab3ap > ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] OT: balun rating exceeded
The following happened to me a few years ago as a brand new ham in my pre-Elecraft days and I wonder if anyone can explain to me the details. I apparently had high swr and exceeded the rating on my balun. It suffered accordingly but didn't completely fail. The result was when I transmitted cw on 40m an internal fuse would blow in the stereo which was on in the next room room. It took two go rounds before I caught onto the cause and effect... A new & better balun cured the problem. At the time I had a Zepp (135') and 4:1 balun at the house entrance. I assume the ruined balun was emitting all sorts of RF that the stereo amplifier picked up, tried to amplify, and couldn't. But I don't understand exactly what would make it draw that much current. Can someone enlighten me? By the way, since then I put up a dipole, halfwave for 160m, about 200' behind the house. That's what I should have begun with. Thanks! Mike ab3ap ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
