+++++++++++++++++ From: "Charlie Hicks" To: Subject: RE: [Elecraft] Any benefits to a Long "Long Wire" Date: Tue, 6 Aug 2002 21:31:07 -0500 About a month ago I put up a 1,000' horizontal loop at about 25' +/- in my pasture. I feed it with about 125' of 450 balanced line and tune it with a Ten Tec 238 tuner. I was going to put up just a single wavelength 160 M loop (just under 500') but the 1,000' fit better in the pasture. It will tune on all bands near 1:1 (except on 160 which is about 1.4:1) and has lots of gain. It is pretty much omni directional - although I haven't done any field measurements. It's the first horizontal loop antenna I have put up and I love it. To be able to tune the entire HF band on a single antenna with quite a bit of gain is real nice. I've had lots of various multiband dipoles, etc. but this beats them all. Looking back over the years I wish I would have tried the horiz. loops before - even if only a single wavelength on 40. They are easy to put up and really don't have to cost much. You can string them through trees, off the sides of houses, etc. The higher the better. I suspect I warm the clouds quite a bit since mine is only at 25' or so - but it sure works well. In the future I'd like to see about putting up some telephone poles. Placed right I would also be able to build a rhombic on the inside of the loop - or perhaps a multi-directional, switchable V. It's amazing what you can do with a length of wire. And it doesn't have to be real expensive. 73, Charlie ----------------------------------- Charlie Hicks Amateur Radio: KOCKH HICKS Systems & Associates, Inc. ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Charlie Hicks'" , Subject: RE: [Elecraft] Any benefits to a Long "Long Wire" Date: Tue, 6 Aug 2002 20:06:04 -0700 I suspect I warm the clouds quite a bit since mine is only at 25' or so - but it sure works well. In the future I'd like to see about putting up some telephone poles. Placed right I would also be able to build a rhombic on the inside of the loop - or perhaps a multi-directional, switchable V. It's amazing what you can do with a length of wire. And it doesn't have to be real expensive. 73, Charlie At 25 feet you should work DX on 14 MHz and up. I do with a doublet at that height. And a "cloud warmer" can be a great antenna for communications at up to 1,000 miles on the lower bands! Ron AC7AC K2 # 1289 ++++++++++++++++++ From: "Stuart Rohre" To: , "'Charlie Hicks'" , Subject: Re: [Elecraft] Good Low Horizontal Loops Date: Tue, 6 Aug 2002 23:05:37 -0500 Loop lovers, I can vouch that a 20 foot high large loop, even on 80m, (660 foot around model we build for Field Day), works out pretty well. We logged Maine on SSB from Central Tx on it, so that is better than cloud warmer range. Also, most of eastern seaboard, midwest ,etc. On the higher bands, we use an 849 foot around one for 20m SSB and at 5 watts, as on 80m above, worked out all over the country, Canada, Latin America, etc. Best DX on FD weekend on that one was Indonesia, not exactly cloudwarmer there , either! Loops are widely misunderstood by hams. Horizontal ones that are more than one wave are modeled as two lobes, neither straight up, and are respectable omni antennas if you have the room. They can be other than square or symmetric and still work well. Just fit them around the edge of the usual suburb lot, and you will have a fine antenna. 72, Stuart K5KVH +++++++++++++++++ To: rondec at easystreet.com, "Ron D'Eau Claire" Subject: RE: [Elecraft] Good Low Horizontal Loops Date: Wed, 07 Aug 2002 14:29:36 -0700 (MST) From: cyr999 at extremezone.com Cc: elecraft at mailman.qth.net I use a 260' horizontal loop up 25' and have worked all over the world. My first antenna, but sure seems to do the job for me. It's fed with open ladder line to a 4:1 baklun and then a short bit of coax to the k2. 73/Tim NZ7C +++++++++++++++++ To: rondec at easystreet.com, elecraft at mailman.qth.net Date: Wed, 7 Aug 2002 14:28:26 -0700 Subject: Re: [Elecraft] Good Low Horizontal Loops From: k6se at juno.com Ron, AC7AC wrote: "These sources say that such a loop has a major lobe straight up, thanks to the gigantic reflector right below it (the earth) with radiation at lower angles dropping way down to zero at the horizon - very similar to a low dipole or any horizontally-polarized radiator only a small fraction of a wavelength above the earth." ========== Although radiation from a low horizontal full-wavelength loop or from a dipole is several dB down at low angles compared to a ground-mounted vertical with a good radial system (or a high horizontal antenna), it still can work DX. W8JI in Georgia finds that his vertical array on 160m consistently outperforms his 300-foot high dipole on DX except on occasions during his sunrise peak when the high dipole is better to VK. Theoretically this is because the ionosphere slopes *upward* to the west at sunrise and enhances the signal from higher-angle radiators. Other stations that have both a vertical and a high dipole notice the same sunrise phenomenon on 160m. 73, de Earl, K6SE ++++++++++++++++++ Date: Wed, 07 Aug 2002 21:16:20 -0400 To: Lloyd Lachow , elecraft at mailman.qth.net From: Hank Kohl K8DD Subject: RE: [Elecraft] Good Low Horizontal Loops - questions At 8/7/02 05:44 PM -0700, Lloyd Lachow wrote: >I could probably string a roughly circular 1K' loop on >my lot, through the trees, with an average height of >about 50'. Cool! >Here's what I need to know, though: >when feeding the loop, is the loop broken, with one >side of the feedline going to each side? Yes >If so, is the >distance across that gap critical? No .... most any insulator will work. >What types of >feedlines would work - which would be best? >Can I use >twinlead? Yes 300 TV twin lead - works fine 450 ladder line - probably works better There is tons of controversy on this - I've used both with great success at 900 mw using dipoles, G5RV's, end fed Zepps, double extended Zepps. > Would I need a balun, an rf choke, or >whatever? Yes, no, no .... in that order! I use an LDG 4:1 balun from a kit they sell. If all you have is a 1:1 balun - try it .... it will probably work! >My rig is a K1 with KAT1, 40-30-20-15. Would one end >of the feedline go to the center conductor, and one to >the ring? While that may work (try it - if it tunes and you can make contacts - it works!) >Would I need counterpoises? Probably not - just ground the radio to a good RF ground >Will the >feedline radiate? Maybe >Is it ok if it does? Yes >My house is roughly in the center, so If the loop were >shorter, the feedline could be shorter (trees >everywhere). >And, perhaps most importantly: I'm now using a >longwire of about 200' that goes every which way, and >works very well - good reports all over Europe, down >to Central America, and domestically. Should I be >satisfied with that, and cease this endless restless >quest for gain? Remembering how the 200' wire is up, take it down, put up the loop. Try it. Sit back with a coffee, tea, Pepsi, and decide which is best! I would never cease a quest for gain!! >Wire antennas are about all that will pass the xyl >review here. >All help appreciated, on or off the list, as I realize >much of this is very elementary to many of you. >73/72, >Lloyd, K3ESE That's how I see it Lloyd. With antennas and me it's always been try it - if it works, keep it. Try something else - if it works better -keep it. And that theory has worked pretty well for the past 40 some years! 73 Hank K8DD */ Hank Kohl K8DD k8dd at arrl.net */ ARRL TS http://www.qsl.net/k8dd */ MI-QRP - Vice Pres. QRP-ARCI - Director */ If God intended you to be on single sideband, he would have given you only one nostril. - Steve, K2PTS ++++++++++++++++ Date: Wed, 7 Aug 2002 21:33:42 -0400 (EDT) From: kc4kgu at EnterZone.Net To: Lloyd Lachow Cc: elecraft at mailman.qth.net Subject: RE: [Elecraft] Good Low Horizontal Loops - questions On Wed, 7 Aug 2002, Lloyd Lachow wrote: > I could probably string a roughly circular 1K' loop on > my lot, through the trees, with an average height of > about 50'. Here's what I need to know, though: Make it 1080ft and you've got a nice 2f loop for 160m! (Not that it wouldn't work very well at 1000ft) > when feeding the loop, is the loop broken, with one > side of the feedline going to each side? Yes. > If so, is the distance across that gap critical? Within reason, I don't think so. How much of a gap were you considering? > What types of feedlines would work - which would be best? That is a matter of great debate. I personally use coax with great success. > Can I use twinlead? I've seen it done with good results. > Would I need a balun, an rf choke, or whatever? That depends again. A full-wave loop has a feedpoint impedence of about 100-ohms. If you are going to be operating at resonance, a 2:1 balun will allow you to use regular coax to feed and maintain great efficiency. With that said, does anyone know where I can find some 100-ohm coax? If you're going to use this antenna on multiple bands, a balun may hurt efficiency. > My rig is a K1 with KAT1, 40-30-20-15. Would one end of the feedline > go to the center conductor, and one to the ring? Yes. > Would I need counterpoises? No. > Will the feedline radiate? If you're operating away from resonant frequency of the loop, using open-wire, twinlead or ladderline, yes. It may even do so with coax but, not as noticable. > Is it ok if it does? That is up to you. I personally try to keep my feedlines as feedlines and radiators as radiators. Some people enjoy this effect to load antennas on multiple bands. > importantly: I'm now using a longwire of about 200' that goes every > which way, and works very well - good reports all over Europe, down to > Central America, and domestically. Should I be satisfied with that, > and cease this endless restless quest for gain? I'll personally never be satisfied. I love working with new antenna designs though. You loop and longwire WILL interact with each other though so, keep that in mind. 73 de John - KC4KGU K2/100 #2490 ++++++++++++++++ To: llachow at yahoo.com, elecraft at mailman.qth.net Date: Wed, 7 Aug 2002 18:56:20 -0700 Subject: Re: [Elecraft] Good Low Horizontal Loops - questions From: k6se at juno.com Lloyd, K3ESE wrote: "I could probably string a roughly circular 1K' loop on my lot, through the trees, with an average height of about 50'. Here's what I need to know, though; when feeding the loop, is the loop broken, with one side of the feedline going to each side? If so, is the distance across that gap critical? What types of feedlines would work - which would be best? Can I use twinlead? Would I need a balun, an rf choke, or whatever?" ---------- A 1000-foot horizontal loop has its first resonant point far below any amateur frequency, however it display resonant points (zero reactance) about every 2 MHz, with the first one in an amateur band at the high end of 160 meters where, if it is a closed loop, the resistive part of the feedpoint impedance is about 100 ohms. On that frquency you could feed it with 50-ohm coax through a quarter-wave section of 75-ohm coax at the feedpoint with close to 1:1 SWR on the 50-ohm line. That however, would make it a single-band antenna, so the best way to feed it would be as a closed loop with 450 to 600-ohm ladder line and use the antenna tuner to match the impedance seen by the transmitter with your "antenna" tuner. This would make it an all-band antenna. The best single-band square horizontal closed loop would be one that has a total wire length of one wavelength. This would be about 270 feet on 80 meters. At resonance, this antenna also has a resistive part of the impedance of 100 ohms, so it can also be fed easily in one of its corners by 50-ohm coax via a quarter-wave 75-ohm matching section at the feedpoint as described above. You wouldn't need to use a tuner with this antenna. ========== "My rig is a K1 with KAT1, 40-30-20-15. Would one end of the feedline go to the center conductor, and one to the ring?" ---------- Connect the ladder line to your K1's tuner as outlined in the manual. ========== "Would I need counterpoises?" ---------- No, not with this antenna. ========== "Will the feedline radiate?" ---------- The currents in the two sides of the balanced line are out of phase with each other and cancel, so there should be no radiation from the line. ========== "Is it ok if it does?" ---------- If it does, it means its balance is disrupted by one side of the line being closer to an object (usually metallic) than the other side. Just take care how you run the line, especially where it enters the house. ========== "I'm now using a longwire of about 200' that goes every which way, and works very well - good reports all over Europe, down to Central America, and domestically. Should I be satisfied with that, and cease this endless restless quest for gain?" ---------- Never cease the quest for gain in an antenna, hi. You never know how a makeshift antenna will work until you try it. Your 200' wire is an all-band antenna, and the loop is a single-band affair (unless fed with ladder line via a tuner). Pick a band to build the loop for and see how it compares with the 200' wire on that band. If the loop outperforms the wire on that band, then keep it. If not, either feed it with ladder line via your tuner and try it on the other bands or take it down and try something else. BTW, you have a *great* CW callsign. If you can drop that first "E" from your call we can become blood brothers <:o) 73, de Earl, K6SE ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Lloyd Lachow'" , Subject: RE: [Elecraft] Good Low Horizontal Loops - questions Date: Wed, 7 Aug 2002 19:47:20 -0700 Lloyd wrote: I could probably string a roughly circular 1K' loop on my lot, through the trees, with an average height of about 50'. ---------- That 50' height is a winner. No wonder you are working tons of DX with a "random wire"! ------------ Here's what I need to know, though: ... is the loop broken, with one side of the feedline going to each side? If so, is the distance across that gap critical? --------------- Ans: Yes and no. ----------- What types of feedlines would work - which would be best? Can I use twinlead? Would I need a balun, an rf choke, or whatever? ------------- A multiband loop is normally fed with "open wire" line such as ladder line or twinlead. The lines with larger conductors and lots of air insulation are best. Twin lead suffers from rather large change in electrical characteristics when it is wet or has ice/snow on it. That can radically change the tuning required, but with using the KAT1 that shouldn't matter. A balun MIGHT be called for if you seem to have a lot of "r-f" on the rig - if touching it changes the tuning, etc. That only happens if you have a high impedance point at the rig on some band. It's hard to predict, but the bigger the loop (or the longer the random wire) the smaller the impedance extremes you will see, and so the less likely you will have trouble that way. --------------- My rig is a K1 with KAT1, 40-30-20-15. Would one end of the feedline go to the center conductor, and one to the ring? --------------- Ans: Yes. unless you want to use a balun to try to make the feeder "balanced". -------- Would I need counterpoises? ----------------- No. ------------- Will the feedline radiate? Is it ok if it does? -------------- Yes, the feeder will radiate unless the currents in the feedline are very well balanced. No, it won't bother the performance as long as your feed line runs 'in the clear' not where the r-f will be absorbed greatly by surrounding objects, or where noise-generating devices and put r-f onto the feeder to interfere with reception. If your feeder tends to run all over the place, I'd suggest using a balun. But under some conditions where you are looking into the wide range of impedances you will see with a multiband antenna like that, baluns can consume a significant amount of power. There are several ops on the reflector here who have done a lot of work with baluns who can offer some additional suggestions. My choice is to avoid them unless I am really concerned about avoiding feedline radiation. --------------------- I'm now using a longwire of about 200' that goes every which way, and works very well - good reports all over Europe, down to Central America, and domestically. Should I be satisfied with that, and cease this endless restless quest for gain? ----------------------- After 50 years of pounding brass, I've come to the conclusion that a "real Ham" is NEVER satisfied with his/her antenna, and spends much of his/her life trying to make one work as well as that one he/she remembers having years ago that pulled in so much DX, Hi! Ron AC7AC K2 #1289 ++++++++++++++++++ Date: Thu, 08 Aug 2002 16:27:05 -0500 From: "George, W5YR" Organization: AT&T WorldNet Service To: Mike McCoy Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] Good Low Horizontal Loops - questions I use #14 THHN house wire for all antennas . . .500 ft for about $15 at Home Depot. 73/72/oo, George W5YR - the Yellow Rose of Texas +++++++++++++++++ From: "Stuart Rohre" To: "Lloyd Lachow" , Subject: Re: [Elecraft] Good Low Horizontal Loops - questions Date: Thu, 8 Aug 2002 17:09:59 -0500 LLoyd, The distance across the feedline attachment point is not critical. It is a small fraction of a wavelength and you do not worry about such effects until they are 0.01 wave length in size. You feed the loop where convenient, corner, or side. There will be some influence on the omnidirectional pattern, but keep it symmetric if you can. An ideal loop is a circle to equally radiate in all directions, but a square will work fine, and triangle, and even a rectangle, until you get quite close on two sides where the rectangle degenerates into a folded dipole. You should try to keep an equal sided arrangement if possible, to work all directions equally well. A random wire that has too many bends and direction changes will have cancellation of part of its radiation. The loop cleans things up, allows all directions to have gain, and is lower noise than an open ended wire or even a dipole. Signals you cannot hear on a dipole because of noise floor will be heard and worked on a large loop. It would be best to use a balanced tuner, or a balun to feed the loop. There is really very little loss from our extensive club use of loops, thru many of the built in baluns in transmatches commercially available. But, it is easy at QRP to build a balanced transmatch also. You could use a balun on the built in tuner to better keep the feeder balance using parallel line. But, some have worked out well just using the coax built in tuner output to feed a balanced line. However, depending on line length, you could get RF problems from that. If the feeder radiates a little it might not hurt at QRP, since hopefully you will route the feeder as clear of other conductors as possible. The gain of a loop operating as 2 wavelengths or more on a band is VERY worthwhile to have, and will give you a commanding signal on the high bands. The double take off lobes are a great way to work all states and work DX with the low angle lobe as well. You are lucky to have all that room and trees; a loop will allow you to make best use of it. 72, Stuart K5KVH The impedance at the feed might be 100 ohms on some bands and something else on other bands. That is why you use a transmatch, as it does not matter; you adjust it out. Also, open wire line is very low loss compared to coax. 450 ohm is lower loss than 300, and that is lower loss than 50 ohm coax. The higher the impedance, the less the loss. An open wire or parallel conductor feeder can operate with high SWR, without a penalty of the mismatch magnitude you would have with coax with all its dielectric. Thus, feed the loop with whatever you have. The antenna is fully balanced, as is a dipole. One way to think of this is the "two sides" simply join at the point opposite the feeder which will be a symmetric point. Thus, as a balanced antenna like the dipole, it does not need counterpoise or radials. It is complete radiator unto itself. The field around the parallel line tapers off in a few diameters. As long as you cross conductors at right angles, there will be minimal effect at metal window sills for example. Ever look at spacers at Radio Shack for 300 ohm line? They are about 6 inches long, as that was sufficient spacing for the VHF TV frequencies. Similar spacing can be provided for HF feeders, using electric fence standoffs which allow 450 line to snap into their holders. They are 5 to 6 inches long, made of black or yellow plastic. Ranch and Farm Stores and some Home Depots carry them with electric fence supplies. Other spacers could be home made from PVC pipe. The Wireman carries one type made from pipe. +++++++++++++++++++++ From: "Stuart Rohre" To: "Lloyd Lachow" , Subject: Re: [Elecraft] Good Low Horizontal Loops - questions Date: Thu, 8 Aug 2002 17:09:59 -0500 LLoyd, The distance across the feedline attachment point is not critical. It is a small fraction of a wavelength and you do not worry about such effects until they are 0.01 wave length in size. You feed the loop where convenient, corner, or side. There will be some influence on the omnidirectional pattern, but keep it symmetric if you can. An ideal loop is a circle to equally radiate in all directions, but a square will work fine, and triangle, and even a rectangle, until you get quite close on two sides where the rectangle degenerates into a folded dipole. You should try to keep an equal sided arrangement if possible, to work all directions equally well. A random wire that has too many bends and direction changes will have cancellation of part of its radiation. The loop cleans things up, allows all directions to have gain, and is lower noise than an open ended wire or even a dipole. Signals you cannot hear on a dipole because of noise floor will be heard and worked on a large loop. It would be best to use a balanced tuner, or a balun to feed the loop. There is really very little loss from our extensive club use of loops, thru many of the built in baluns in transmatches commercially available. But, it is easy at QRP to build a balanced transmatch also. You could use a balun on the built in tuner to better keep the feeder balance using parallel line. But, some have worked out well just using the coax built in tuner output to feed a balanced line. However, depending on line length, you could get RF problems from that. If the feeder radiates a little it might not hurt at QRP, since hopefully you will route the feeder as clear of other conductors as possible. The gain of a loop operating as 2 wavelengths or more on a band is VERY worthwhile to have, and will give you a commanding signal on the high bands. The double take off lobes are a great way to work all states and work DX with the low angle lobe as well. You are lucky to have all that room and trees; a loop will allow you to make best use of it. 72, Stuart K5KVH The impedance at the feed might be 100 ohms on some bands and something else on other bands. That is why you use a transmatch, as it does not matter; you adjust it out. Also, open wire line is very low loss compared to coax. 450 ohm is lower loss than 300, and that is lower loss than 50 ohm coax. The higher the impedance, the less the loss. An open wire or parallel conductor feeder can operate with high SWR, without a penalty of the mismatch magnitude you would have with coax with all its dielectric. Thus, feed the loop with whatever you have. The antenna is fully balanced, as is a dipole. One way to think of this is the "two sides" simply join at the point opposite the feeder which will be a symmetric point. Thus, as a balanced antenna like the dipole, it does not need counterpoise or radials. It is complete radiator unto itself. The field around the parallel line tapers off in a few diameters. As long as you cross conductors at right angles, there will be minimal effect at metal window sills for example. Ever look at spacers at Radio Shack for 300 ohm line? They are about 6 inches long, as that was sufficient spacing for the VHF TV frequencies. Similar spacing can be provided for HF feeders, using electric fence standoffs which allow 450 line to snap into their holders. They are 5 to 6 inches long, made of black or yellow plastic. Ranch and Farm Stores and some Home Depots carry them with electric fence supplies. Other spacers could be home made from PVC pipe. The Wireman carries one type made from pipe. +++++++++++++++++ To: rohre at arlut.utexas.edu Cc: kc4kgu at EnterZone.Net, llachow at yahoo.com, elecraft at mailman.qth.net Date: Thu, 8 Aug 2002 18:55:51 -0700 Subject: Re: [Elecraft] Good Low Horizontal Loops - questions From: k6se at juno.com Stuart, K5KVH wrote: "One of the great myths of ham radio is that parallel lines radiate or couple and coax does not. Misapplied, either can radiate. The field from a balanced line, is just that, balanced, and should be minimal a few diameters away. The coax should not have current on its outside shield, but it WILL if it is connected to an antenna that is nowhere near its impedance and if the line is for example, a quarter wave long between rig and antenna or an odd multiple of a quarter wave." ---------- Kudos to Stuart for pointing this out. Some statements by others on this reflector were erroneous on this subject and they seemed to ignore my previously post about the subject. Stuart's statement is indeed correct and is much more eloquent than mine was. ========== "A good rule of antennas is to feed balanced antennas with balanced line. An unbalanced antenna such as mobile whip, quarter wave ground mounted vertical, and gamma matched beams are unbalanced feeds where coax is useful, if you can confine all fields inside it." ---------- As Stuart said, it's "a good rule", but not absolutely necessary. Balanced antennas can be fed with coax and work fine, but to make sure there are no common-mode currents on the line you should use a choke balun at the feedpoint. Most often, a choke balun is made from winding the last few feet of coax near the feedpoint into a coil of several turns about 6" in diameter. Another way is to use a number of ferrite cores made for use on the outside of the coax. Of course, a commercial 1:1 balun will do the job also. Feeding loops with coax and bringing the 100-ohm feedpoint impedance down to 50 ohms by use of a quarter-wave length of 75-ohm (which acts like a transformer) is quite common practice and a choke balun would improve the common-mode rejection on this feed method as well (although it's not absolutely necessary). Consider any antenna fed with coax as a single band antenna (except when using the antenna on its 3rd harmonic, i.e., a 40-meter dipole of vertical cut for the CW portion of the band is also resonant as a 3/2-wave dipole or 3/4-wave vertical on the high end of 15 meter with a reasonable SWR on the feedline. Stuart also mentioned that an antenna need not be resonant to radiate efficiently. This is very true, but such antennas *must* be fed with Hi-Z balance line via a tuner (remenber, the feedline does NOT radiate if care is taken in its installation so as not to disrupt its balance). The convenient thing about resonant antennas is that they can be fed with coax (the way I prefer to do things, i.e., conveniently). 73, de Earl, K6SE ++++++++++++++++ Date: Fri, 09 Aug 2002 00:05:10 -0500 From: "George, W5YR" Organization: AT&T WorldNet Service To: k6se at juno.com Cc: wa7gxd at fidalgo.net, elecraft at mailman.qth.net Subject: Re: [Elecraft] Good Low Horizontal Loops - questions Standing waves are a differential-mode effect and do not evidence themselves on the outside of the coax braid. There are no "high-amplitude standing waves on the (outer) shield of the coax." All standing-wave phenomena are confined to within the coax. The only times that radiation occurs from the outer braid is (a) when the braid is not brought away from the antenna properly and signal is induced into it to produce common-mode current and radiation and/or (b) an unbalanced line is used to feed a balanced load without benefit of a balun to isolate the outer braid. Resonance has nothing to do with the presence of common-mode current on the outer braid and lack of it does not cause feedline radiation. That is strictly a balanced-current problem with balanced lines and a common-mode current problem with coax. A balanced line does not ensure no feedline radiation. What counts is balanced currents in the two wires of the feedline. A visit to "Reflections II" by W2DU is recommended. 73/72/oo, George W5YR - the Yellow Rose of Texas Fairview, TX 30 mi NE of Dallas in Collin county EM13qe Amateur Radio W5YR, in the 56th year and it just keeps getting better! QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735 Icom IC-756PRO #02121 Kachina 505 DSP #91900556 Icom IC-765 #02437 k6se at juno.com wrote: > > I wrote: > > "If you feed an antenna for use on all bands, those bands it is not > resonant on will have current on the coax feedline shield and the coax > will also radiate -- an undesireable trait. The feedline will not > radiate if you use a balanced feeder." > ========== > The "current" I'm referring to here is the high-amplitude standing waves > on the shield of the coax. Balanced line will also have these big > standing waves (on both sides of the line), but the currents in the two > wires in the feeder are 180-degrees out of phase, effectively cancelling > the feedline radiation. +++++++++++++++ From: "Stuart Rohre" To: "George, W5YR" , Cc: , Subject: Re: [Elecraft] Good Low Horizontal Loops - questions Date: Fri, 9 Aug 2002 17:30:17 -0500 I prefer to refer to twin conductors as parallel line, since indeed, balance is not guaranteed by its use. Balanced line is only balanced if the currents are equal in both sides. At an unbalanced source, you would not expect to be able to gain equality in the current in the parallel feeders. Fascinating however, was the L. B. Cebik computation or measurement of Zepp feeders. He found that the open circuit side of the parallel line was only 10 per cent out of equality with the side connected to the end of the half wave antenna. At least, that is the way it read. A pair of current meters would help one check line balance, as they would equally upset the two sides of the line, and at least allow a relative comparison. A good experiment would be to see what line current you read with one meter of a pair, and no meter in the other side of the line; and then connect both meters, one in each leg, the same distance along the parallel line. (Am looking for my collection of meters now with the thought of comparing the Les Moxon indictment of End Fed Zepp type antennas to other Off Center Fed types.) There are installations that are more easily handled by off center feed or end feed. However, from modeling various OCFs, as Cebik has done, I think the penalty of end feed is a distortion of the radiation pattern, and I prefer to have a near omni pattern. Those nearer one coast or the other may well benefit from end feeds or OCF feed, if you wish to favor land side rather than ocean. But, this brings up another fascinating question. Does an OCF antenna at the beach gain back pattern on the short side, if that side is nearer the water? That is, with the wire at right angles to the surf line. No single antenna is sufficient for all ham use. Some come closer to our objectives at a band or time, (such as working DX) than others. But, if limited space or limited numbers of antennas are the requirement, there are variations on balanced antennas that will give one a combination of DX capability and short skip operations. Our local club's contribution to the art of horizontal loops is treating the legs as individual pieces of wire, easing the installation of massive amounts of wires. Operationally, they work just like the models with continuous corners, where ours are joined by simple mechanical splicing with wire nuts. Out West we know of an installation using 80 foot towers that also uses wire nuts for balanced feeder connections to antennas, and the owner does not have maintenance problems; thus, it is even useful for longer than Field Day type installations. 73, Stuart K5KVH +++++++++++++++++ From: "Stuart Rohre" To: Cc: , , Subject: Re: [Elecraft] Good Low Horizontal Loops - questions Date: Fri, 9 Aug 2002 17:59:07 -0500 All very true Earl, but I am a convert to the concept that parallel feeders can be as convenient as coax and at less cost! The more I have used them in Field Days, the happier I am with them. We have used all parallel line feeders at club field days since 1996, using Double Zepps, horizontal vee beams, and finally settling on larger than one wave, (at lowest band), low horizontal loops for multi band use. We have sometimes had more line than needed to reach from antenna feedpoint to rig, and have draped them over tree branches, or tied them from string to tent frames, all without RF in the shack complaints, or any apparent effect on signal strengths either heard or transmitted. Our contact totals go up every year as we add more bands and loops, and we believe we have had better results with the parallel line feeds. Both 300 ohm slotted ribbon and 450 ohm ribbon, (ladder line), have been used. The longest feeder is usually 110 feet or so. Of course, in the Field Day use, we are aiming for multiband antennas, and would not put up such a large loop for only one band, except we usually have a station on 20 the whole time. With the use of a few easy to make or buy standoffs, the parallel line can be used in the home station and still be less cost than the coaxes, and give you lower losses in mismatch cases, and that has been important for QRP to our club use. After several Field Day misadventures with bad coax jumpers, we have come to like the positive simplicity of our wire nut connections to join parallel line to antenna pigtails, or to line extensions, or simple bolt connections on transmatches. It has been a joy to not have to solder a coax connector at Field Day for some years! :-) Of course, you do have to wax your parallel line insulation to shed water effects; but then I have drained water out of coax lines, too. We usually abandon operations in storms, too many lightning bolts down here, thus we do not see the rain effects that may happen to parallel lines. IF however, the transmatch setting changes due to rain, that is something one can monitor and easily correct. We had to correct a transmatch this Field Day just past because of it heating up from Sun beating on its dark case! In multi band operations, due diligence is needed for either type of feeder. 73, Stuart K5KVH ++++++++++++++++