+++++++++++++++++++++ From: "Dennis Ponsness" To: "Low Power Amateur Radio Discussion" Sent: Saturday, September 01, 2001 9:14 AM Subject: Ladderline ?? > > > OK wise and noble gurus, I have a question that I have not been able to find > a specific answer to... I have aluminum siding on my house sooo... how far > do I REALLY need to offset the ladderline from the siding? And is the > optimum distance the same for 300 ohm TV and 450 ohm "good stuff"? > > I have seen figures from 3 inches to 8 inches, so as you can see I am > "confused". I will be shortly starting on my fall antenna projects and > such, so I want to make sure I do it right the first time! No fun doing > antenna work in mid-january in northern Michigan!! > > TNX es 72 > > Dennis - WB0WAO Hi Dennis, The rule of thumb is 3X the distance between conductors.. so the answer to one of your questions is it the same for 300 or 450 ohm line is no This is a minimum figuire. 300 Ohm would be about 1.5 inchs and 450 ohm would be about 3 inchs Ruffly speaking.. 600 ohm would be about 18 inches.. Hope this helps 73 Dave KC1DI +++++++++++++++++++++++ Date: Sat, 1 Sep 2001 12:37:35 -0500 From: Nick Kennedy To: "'wb0wao at hotmail.com'" , Low Power Amateur Radio Discussion Subject: [106222] RE: Ladderline ?? Message-ID: <01C132E2.E17196C0.nkennedy at tcainternet.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hello Dennis-- I don't know what the accepted rule of thumb is, but it would be good to be say, 5 times the spacing of the conductors. Ten would be better. We're assuming you are running parallel to sheet metal. I think when penetrating it at right angles, you can have much smaller spacing. (I've got about 1/2 inch on my 450 ohm line, doing this.) Some technical basis. Balanced parallel lines don't radiate. Why not? Well, you've got the same current going in opposite directions, each tending to produce a field. The fields being opposite, cancel. But what if you're closer to one conductor than the other. Take a good case first. Conductor spacing of 1 inch and we're at a point 10 feet away in the plane of the feedline, so one conductor is 120 inches away and the other is 121 inches. Field strength varies with the square of the distance, so the ratio of the strengths is (121^2) / (120^2), or 1.017. Or 1.7% away from being identical. Pretty good cancellation. Now, look at 3 inches away from one conductor and 4 from the other. Ratio of fields is (4^2) / (3^2) or 1.78. Here the cancellation isn't so good at all. So when you get close to the line, cancellation isn't so good (unless you're symmetrically the same distance from each conductor), there is a field present, and it will induce currents in nearby conductors. Being in the plane of the conductors is worst case, since you maximize the difference in distance between the point of interest and the two conductors. So, I'd think having the line parallel to the structure should help. Never seen that stated anywhere, I'm just thinking out loud. One thing I have seen done is to put some twists in the line. The idea is that you induce a current one way here, then a couple feet away, after a twist, you induce an opposing current and they cancel. Probably useful if you're making a long run along a conductive surface. This should also make currents induced in the line from the antenna's field tend to cancel. And since 300 ohm line has closer conductor spacing, you can get closer to it for the same degree of uncancelled field. Translation: more spacing needed on the 450 ohm line. 72--Nick, WA5BDU +++++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Elecraft" Subject: RE: [Elecraft] Ladder Line near the gutter. Date: Mon, 11 Feb 2002 09:17:45 -0800 Dan, WG4S, asked: > I need to secure the line from wind movement anyway, so my > question is this. How far from the metal gutter should I secure > the line? I've not seen any literature (although I'm SURE it > exists somewhere) as to how far to make it. I've definitely seen > admonitions not to run the line against any metal. The "rule of thumb" published in the ARRL handbooks for many years was this: "The minimum separation between either conductor and all other wiring should be at least four or five times the conductor spacing..." That would include any conductor or any lossy dielectric. The earth is a very lossy dielectric. Keep the open wire line well away from it to avoid using your r-f to warm the earthworms. The idea is to keep the two currents in the open wire line equal and out of phase at all points. If you accomplish that, the open wire line will not radiate significantly. The field created by current flowing in one wire will exactly cancel out the field in the other wire. In theory, that will only be true of both wires are exactly in the same place - an impossible situation. In practice, the cancellation over the HF range is excellent provided the spacing is on the order of 2 to 6 inches (5 to 15 cm) with the narrower spacing preferred on 28 MHz. Feeding the open wire line from a balanced source and connecting it to a balanced load at the antenna are two steps toward having a balanced and out-of-phase current in each line. If you allow the line to run where one conductor can capacitively or inductively couple to surrounding objects more than the other conductor, you will also introduce unbalance as well as lose r-f. So wherever you are running it, try to keep it away from objects and keep each conductor equidistant from whatever objects you must pass close by. Also, try to pass objects at right angles to minimize the amount of coupling. If you are planning on running the line at a high SWR, keep in mind that very high voltages can exist at points along the line. Separation and insulation are very important, not just to avoid losses but to prevent the possibility of starting a fire in combustible material. A little dust on the insulators holding the wires or against something they are touching and you can have a flashover that can start a blaze. Not a happy prospect, especially in a hidden corner of an attic. Those high voltages are also why true open wire line, with a minimum of high quality insulators holding the wires, is far preferable to the common 'ladder line' or, worse, 'twin lead'. Where the wires do have to touch something, such as the spacers holding them, you want the very best insulation you can get. Ron AC7AC K2 # 1289 +++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Elecraft" Subject: RE: [Elecraft] Ladder Line near the gutter. Date: Mon, 11 Feb 2002 09:40:29 -0800 Luckily I have a fire extinguisher. But at five watts, I > may not need it. I think I'll use PVC elbows, toggle bolts, and > discuising paint.> > Dan / WG4S / K2 #2456 True, but I have melted plastic insulators on open wire line at about 10 watts when they happened to be right at a high impedance point! Fortunately, that was at the banana jacks on the back of my ATU where the line terminated, so I could smell it as well as see it on the SWR meter in the line to the ATU. Use the best insulation that you can get at all points. If you can find them, those old ceramic feed-throughs that were used for "knob and tube" house wiring years past ought to be excellent for guiding the conductors through a wall. That's exactly what they were designed for although at 60 Hz instead of HF. Every time I come across one I pick it up and put it in the antenna goodie box. Ron AC7AC K2 # 1289 ++++++++++++++++ From: "Stuart Rohre" To: "Dan Barker" , "Elecraft" Subject: Re: [Elecraft] Ladder Line near the gutter. Date: Mon, 11 Feb 2002 15:07:12 -0600 A good means to standoff is the Radio Shack standoffs for 300 ohm twin lead that are about 7 inches or longer. Some screw into wood, or clamp to mast. PVC ones can be made. Home Depot sells electric fence standoffs in a bag of 25 for $5 or so. The rule of thumb is at least twice the spacing of the line, but since you are crossing at right angles, it is minimal interaction anyway. 73, Stuart K5KVH ++++++++++++++++ From: Bob Tellefsen [mailto:n6wg at earthlink.net] Sent: Tuesday, February 19, 2002 7:53 PM To: Dan Barker Subject: RE: [Elecraft] non-Wire antennas Hi Dan Think of "a little" as being frequency sensitive, like about 1/16th wavelength. On 10m that would be about 2 ft, while on 80m it would be more like 33 = ft. The main idea is to move the transmitter feedpoint away from a very high impedance point on the feed line. As an example, consider a 40m halfwave dipole fed with 450-ohm line. If = the antenna is pretty close to resonant, and the feedline length is adjusted = for a current maximum (lowest impedance) at the shack end, it will be very = easy to match and load. The feedline will be a halfwave long under these conditions, repeating at the shack what it sees at the antenna. Now = shift to 20m. The 40m halfwave dipole is now two halfwave dipoles on 20m, center fed = at a high Z point. The feedline is now 2 halfwaves long, and that high = impedance is repeated at the shack end. If you add about 1/16th wavelength of = line, it will lower the impedance enough for fairly easy matching. I use 450-ohm line as my feeder on my multiband dipole. To change = bands, I plug in an extension section of line to bring the low Z feedpoint back = to the end of the line. I Use banana plugs and jacks to make the line = addition quick and easy. Hope this gives you an idea or two. 73, Bob N6WG Newark, CA on SF Bay +++++++++++++++++++ Date: Mon, 25 Feb 2002 14:57:34 -0600 From: "George, W5YR" To: jakidz at pullman.com Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] OT - Twinlead and matching? I use 450-ohm ladderlin on three wire antennas here and use banana plugs and jacks on each one to go into W2DU bead baluns for transition to coax into the shack. I operate mostly at 5 watts and occasionally at 100 watts, so there is no power problem for me. Idoubt that the "insertion loss" could be measured at those power levels. I would be concerned about using small banana connectors for a 1500+ watt station, however. I think that a direct soldered connection would be the most reliable. Depending upon the antenna, frequency and line length, a high SWR on the 300 ohm line could place a current maximum at the line feedpoint and really stress the connectors. Similarly a voltage maximum could occur in which case the insulation becomes a consideration for handling the voltage. For that reason I use RG-213 coax even at the 100 watt level since the SWR in the coax can become quite large on some bands, and even with only 100 watts the voltage rating of smaller coax could be challenged. I prefer the 1:1 current or choke balun for the transition as I described above. My three wires work well on all bands with no common-mode current problems. 72/73/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 Icom IC-756PRO #02121 Kachina #91900556 IC-765 #02437 All outgoing email virus-checked by Norton Anti-Virus 2002 jakidz at pullman.com wrote: > > Greetings: > > With respect to insertion loss, are banana plugs the best way to connect > sections of twinlead together for HF? Any better ways that are relatively easy > to disconnect and reconnect? > > Any suggestions on the most efficient means of making the transition from > balanced 300 ohm to unbalanced 50 ohm? > > Thanks. > John, KD7OIU > K2#1932 +++++++++++++++++++ Date: Mon, 4 Mar 2002 20:23:32 -0600 From: "Stuart Rohre" To: Cc: Subject: [121298] Another way of handling parallel line to avoid coupling any imbalance Just twist the parallel line or window line every 18 inches or so, and any untoward influences will balance out, as both conductors will be exposed to the source. Inside, you can space the twin line, a few diameters away from surfaces. Radio Shack still sells standoff insulators that are long enough to handle this even for the 450 ohm window line. Just do not run close to other conductors if you can help it. Since you are hooking parallel line to the rig thru a transmatch and balun anyway, or at least a transmatch and cable choke with floating chassis trans match, you can adjust out any transitions to window thru bolts, or other conveniences in handling the parallel balanced conductors. The efficiency of using parallel lines is great, and they work even in high SWR situations with lowest loss. 72, Stuart K5KVH +++++++++++++++++++ Date: Mon, 4 Mar 2002 20:30:26 -0600 From: "Stuart Rohre" To: Cc: Subject: [121300] Easy spark gaps for parallel line It is good someone mentioned spark gaps placed outside the entry of parallel line to the shack. The easy spark gap for hams is to get a couple of old spark plugs. Place them side by side in a copper plate, or aluminum if that is all you have. Hook the screw tops to your parallel lines, and set the gaps so that they do not arc over with your power. Actually, whatever they were worn to, is fine, as they will break over as a storm builds up static on your antenna. The plugs can be screwed into a tight hole in the plate, no threading needed. Use a flat strap to ground the plate to earth at a suitable ground rod or radial terminus. (crowfoot ground). The old handbooks show the plate mounted on insulators to prevent the plate under a fault from arcing to the window frame, house wiring ,etc. 72, Stuart K5KVH ++++++++++++++++++++ Date: Mon, 11 Mar 2002 17:10:47 -0500 From: "ss lyon" To: , "Low Power Amateur Radio Discussion" Subject: [121850] Parallel Feed Line: HB vs Commercial I agree that there isn't a lot of difference in performance between solid / window line on one hand and true ladder line on the other hand -in good weather and with shorter runs. But I make most of my parallel feed line now since I've moved to Maine. A point that hasn't received adequate attention is that ice loading is a real problem with commercial "window" line. It causes mechanical failures including broken line, pulled out support insulators, broken siding and downed antennas. Also, detuning due to rain, snow and ice is severe compared to (my) home brew "ladderline", esp. on long runs. My longest feeder goes 270' up hill and into the woods, then 60' up to the 250' end fed zepp. Currently available commercial stuff doesn't do well over that distance without a whole bunch of supports, and really troublesome tuning changes with weather. A method to make robust HB Parallel Feed Line is described in an article published in NJQRP Home Brewer last year. It's tricky to get the manufacturing process down, but with patience and enough libation, a 250' batch can be made in a little over four hours. The results are well worth teh effort. 73 AA1MY Seabury & Sharon Lyon 99 Sparrowhawk Mtn Rd Bethel ME, 04217 U.S.A. 207-836-2576 ++++++++++++++++++ Date: Tue, 12 Mar 2002 09:14:20 -0500 From: "Pastor-KC1DI" To: , "Low Power Amateur Radio Discussion" Subject: [121899] Re: Real Windowline ? ----- Original Message ----- From: "DeniGm3skn" To: "Low Power Amateur Radio Discussion" Sent: Tuesday, March 12, 2002 8:40 AM Subject: Real Windowline ? > Where can I obtain real *copper* conductor 450 ohm windowline? I have tried > some of the copper plated steel conductor type and I am less than impressed! > Far too brittle, too thin about (22SWG) fractures often, the micro thin > copper plating invariably gets damaged, fails and the steel then rusts, > complete waste of time money and effort. I believe in the USA there may be > some high quality windowline available with stranded (or perhaps solid) 12G > COPPER conductors, is this generally available in the USA? I would like to > buy some before I resort to building my own ladderline with copper wire and > spacers. Thanks for your help,73 > Deni, Gm3skn > The only K2 in Shetland Islands UK > > > Here is the URL for one source of manufactured 600 ohm line 73 Dave http://www.w7fg.com/ant.htm +++++++++++++++++++ Date: Tue, 12 Mar 2002 10:25:39 -5 From: "Bill Kelsey - N8ET - Kanga US" To: "AI2Q Alex" , qrp-l at Lehigh.EDU Subject: [121905] RE: Ladder Line > Does anyone know what does W7FG use for spreader insulators? There is no > indication on his Web site of the quality or construction of his ladder > line. Alex and QRP-L - I resell the W7FG ladder line and have some stock available if anyone needs some. The spreaders are made from black irrigation tubing that is 3/4" diameter. The spacers are 4" long, and the wire spacing is 3 3/8". The spacers are placed about 18 - 20" apart on the line I am looking at right now. The wire used is multi-stranded, very flexible copper with black insulation. 73 - Bill - N8ET Kanga US kanga at bright.net http://www.bright.net/~kanga/ 419-423-4604 +++++++++++++++++ Date: Tue, 12 Mar 2002 14:09:36 -0500 From: "AI2Q Alex" To: "'Don'" Cc: "QRP-L (E-mail)" Subject: [121922] RE: Ladder Line Don: My open wire feedline uses 3/8-in. plastic rod. It was given to me by WA1VOH, in 4-ft. lengths. I put samples of it in my microwave oven for an absorption test, and it didn't get warm, so I used it. It works very well. I cut the rod into shorter spreader lengths, and then slit the ends with a hacksaw to accept the wire. I also placed each spreader in my drill press and bored holes at right angles to the slits. These holes hold the keeper wires in place. Each keeper is soldered to the main feedline at each end of the spreader. It looks and works great! Vy 73, AI2Q, Alex in Kennebunk, Maine QRP-L 687 .-.-. +++++++++++++++++ Date: Wed, 13 Mar 2002 20:44:20 -0500 From: Dave Richards To: "Low Power Amateur Radio Discussion" , weinfurt at oak.cats.ohiou.edu Subject: [122021] Re: Making your own LadderLine Message-ID: <54YU5MLNHLIZYED3VTPTRJIB9D8XVQM.3c900074 at sony> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Greg, That IS Cool! Dave W1QB 3/13/2002 12:58:37 PM, Greg Weinfurtner wrote: >Hi all, > I've come up with a simple way to make your own ladder line >which is very durable and easy to do. Check out the page at: > >http://oak.cats.ohiou.edu/~weinfurt/LL.htm > > > >73 de NS8O >-- >Greg Weinfurtner <>< > PC Support Specialist > Gordy Hall Room 017B > Modern Language Dept. > Ohio University Athens > > GO BOBCATS! > > 1-740-593-0478 > gweinfurt1 at ohiou.edu ++++++++++++++++++ Date: Thu, 14 Mar 2002 14:15:48 -0500 From: Bill Coleman To: , "Low Power Amateur Radio Discussion" Subject: [122085] RE: W8DIZ in a Dizzy On 3/12/02 5:26 PM, KKANALZ at prodigy.net at KKANALZ at prodigy.net wrote: >As far as "oozing" goes, the boiling-in-paraffin pro- >cess requires that the dowel separators stay in >the "bath of paraffin" for quite some time to ensure >that it's well permeated before you take them out to >drain. There was a great thread on creating open-wire spacers on TowerTalk a couple of years ago. I posted a summary there. See: K7GCO claimed to have done a number of experiements with different open-wire spacer materials. He specifically said to avoid wood spacers. Wood soaks up moisture and causes leakage. Not what you want in an insulator. And boiling them in paraffin doesn't help. Lexan, Delrin or even plastic coathanger (ABS??) works just great. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 +++++++++++++++++++ Date: Thu, 14 Mar 2002 20:31:38 -0700 From: "James R. Duffey" To: Subject: [122139] Open Wire LIne and Spreaders - A Cynics View After several go arounds with home made open wire line, I have decided that given the relatively low cost, and in my application reasonable performance, of the "450 Ohm" ladder line, open wire line is not worth the effort. I have made the open wire line from hard drawn wire, enameled magnetic wire, and some hookup wire in gauges ranging from 14 to 22. The size and type of wire you use doesn't make much difference. Good spreader materials are hard to find. Plastics designed to be used indoors generally depolymerize rather quickly outside, at least at my altitude (7000 ft). This includes the plastic coat hangers, hair curlers, and theme paper binders. I had the best luck with the grey PVC pipe made for electrical conduit. This does make rather heavy feedline though. You can also buy UV resistant plastic stock, either round or square, to make your own. It is hard to place the spacers evenly without introducing twist in the line. It is best to keep the open wire line under tension when being used. In practice, open wire line, as well as the modern ladder line, will not exhibit the low loss often quoted. Dust, pollution, wind, and moisture all conspire to increase loss. None the less, either open wire line or ladder line will have lower losses than commonly used coax such as RG-213 or RG- 58. Until it rains. Then the ladder line and open wire line will both exhibit increased losses, but the ladder line will be worse. New Mexico is rather dry, so those days when it rains or snows are few and far between. If I lived in the Northweest, or southeast, I am sure that I would have a different opinion. Both coax and ladder line have their adbantages and disadvantages. I uusually replace one with the other when I am changing antenna systems. - Dr. Megacyle KK6MC/5 -- James R. Duffey KK6MC/5 Cedar Crest, NM DM65 +++++++++++++++++++ Date: Fri, 15 Mar 2002 00:28:57 EST From: W2SH at aol.com To: qrp-l at Lehigh.EDU Cc: KKANALZ at prodigy.net, wb4mnf at alt.org Subject: [122149] Homebrewed Open-Wire Feedline Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit I decided to undertake ladder construction because of my utter dissatisfaction with what is commercially available. A dozen years ago at a hamfest I bought some #14 enameled solid copper with 5/16" diameter polystyrene spacers heat fused to the wire. The seller said that it was commercially made and had been stored for years in his attic. I had never seen this feedline before or since. I was only able to buy his 75-foot roll, but it worked out well. 20-30 years ago there was sold solid copper wire feedline with white plastic insulators about 1 1/4" long and 3/16" diameter. This was crap. The enamel insulation and the spacers both cracked after a few months outside. I presently require a 180-foot long feedline. I got some solid #14 enameled wire manufactured by Phelps Dodge, but the insulation didn't hold up. Varnishing the wire with $23-a-quart marine varnish didn't work for very long. What is now showing great promise is bare solid copper wire with three coats of rust proof paint. This paint is latex based and has worked beautifully for me painting iron railings and anything metal that lives outside. I remember as a kid seeing open-wire feedlines with wax-impregnated wooden dowel spreaders. If it worked for the OTs, well why not for me? I combed through QST for the 1920s and 1930s. I noted (but unfortunately ignored) a couple of comments saying that such spreaders didn't hold up very long. Somewhere else I read that a mix of two parts beeswax to one part paraffin was what was best. I have long respected bamboo as having a very high strength-to-weight ratio. I also like to eat Chinese food. So, you guessed it, I started pocketing my eating instruments after the meal, much to the amusement of the restaurant waiters. At any Chinese grocery bamboo chopsticks are available in a variety of shapes and sizes, as cheaply as 500 for seven bucks. I bought a bunch. I sized their diameters with a drill bit gauge and eyeballed them for straightness. I discarded nearly half of the lot. I cut the keepers to two-inch lengths, and drilled and notched their ends. I baked about 200 of these spreaders in a 180-degree F. oven for 24 hours to drive out any moisture. Then they were cooked in the wax mixture for half an hour. The first batch cooked at too high a temperature and came out dark brown. I then got a candy thermometer and limited the wax temperature to 180 degrees F. (paraffin melts at about 110 degrees F. and beeswax at slightly less). Wax is inflammable so I used a large high-sided stock pot and was careful. I kept peace in the family by really cleaning up the kitchen afterwards. I mounted the spreaders to the paralleled conductors stretched between two trees. Eschewing metallic ties, I used braided Dacron 50-lb. test kite line to lash the spreader to the wire with a constrictor knot. I left the feedline out all winter. The bamboo spreaders and kite line ties both held up, but the wax impregnation on the spreaders and the varnished enamel insulation on the wire did not survive very well. The newest batch of bamboo spreaders was baked dry for 24 hours, then dunked in hot linseed oil thinned with paint thinner. When dry, they were dunked four times in the expensive marine varnish with two days' drying time between dunkings. They've held up well outside this winter, as has the painted wire. Now it remains to construct the feedline by putting the two together. The wax mixture in the stock pot has been used most successfully to impregnate my rope halyards. The brief moral to this long story: those two guys who wrote to QST 65-70 years ago were right--wax impregnated spreaders don't last a long time. Have I done the right things? Certainly not all of them. But I've learned a lot, and bamboo is a lot cheaper than Teflon rod. 72/73, Charles, W2SH +++++++++++++++++++ Date: Fri, 15 Mar 2002 05:43:45 -0700 (MST) From: "Karl F. Larsen" To: Cc: Low Power Amateur Radio Discussion Subject: [122155] Re: Homebrewed Open-Wire Feedline Charles, I fail to see why your interested in 600 ohm feed line. I use 450 ohm ribbon that is a plastic that holds up in the Hot New Mexico sun for many years. My 40 meter vertical is held up with hay binding plastic rope. This rope I got a mile of for $25. It is a lite brown color and the box says it will withstand field conditions for 10 years. It has a breaking strength of 350 pounds. I recall going to a Ham store in South Los Angeles in about 1949 and buying ceramic spreaders that had a half circle on each end for the wire to ride in and a hole in the ceramic so you can tie the wire to the ceramic with smaller wire. The antenna was a end fed zepp and knowing what I know now, 300 ohm ribbon would work well too. Of course you could not find 300 ohm ribbon in 1949. ++++++++++++++++++ Date: Fri, 15 Mar 2002 07:24:37 -0700 From: William R Colbert To: qrp-l at lehigh.edu Subject: [122160] Re: Homebrewed Open-Wire Feedline For those still interested in the ceramic type spreaders, Daburn Electronics and Cable still has all sorts of ceramic type insulators, including the 2 inch spreader types for making open wire feeders. They also make a very nice dipole type insulator which has a top section for rope or wire attachment away from the radiating wire holes. Very strong - used one to support a 300 ft vee beam. Additionally, Daburn has lots of antenna type wire, actually wire of all types. Haven't ordered anything in recent times so don't know if they are cost effective, but their catalog is on line at: http://www.daburn.com/~daburn/home.html My E&E Handbook 1946 edition and the E&E Antenna handbook both make reference to 300 ohm line. And in my 1947 ARRL HB, Amereican Phenolic shows an ad for 72, 150 and 300 ohm twin lead. They also had a replacement polystyrene window pane ready to drill and replace a glass pane near the operating position. 73 Ray A penny saved is a government oversight. Ray Colbert, W5XE, OOTC#3618, SOWP#1064M NARTE-NCT2R FP# 111, SOC#78,QRP-ARCI 5784, El Paso,(FAR WEST)TEXAS ++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: Subject: RE: [Elecraft] Switching P/S Horror Stories Date: Fri, 5 Apr 2002 14:45:40 -0800 > ...I have one antenna fed with ladder line that interferes with everything > else in the house... > Alex N4BYJ Keep in mind that it is not the ladder line itself that is causing the interference, but the fact that the currents flowing in the wires are not balanced. If you have the ladder line balanced, it will not pick up or radiate r-f. If you are using some sort of off-center fed antenna, then the ladder line is being used as part of the radiator, not as a feed line. Windoms are one of the common off-center fed doublets. They use the ladder line as a integral part of the radiator to provide vertical radiation. Those designs bring the radiating and receiving part of the antenna right down to the ATU. You should not expect it to be any less sensitive to noise pickup or radiation than a single-wire feeder. If you want ladder line to work as a transmission line, like coax, that minimizes radiation or pickup, you must terminate it in a balanced load at BOTH ends. If you have a balanced load at the far end (e.g. center fed doublet) and you are seeing a lot of radiation or noise pickup, you probably do not have a balanced feed at the ATU end. IF you are using a balun, that's the first thing to suspect. Doublets where one end is a lot closer to the ground or metallic objects than the other can cause an unbalanced termination. Feeder runs where they run alongside metal, and other effects can also upset the balance and cause the feeder to both radiate and pick up noise. Ron AC7AC K2 # 1289 +++++++++++++++++++ Date: Wed, 12 Mar 2003 18:06:04 -0500 From: Rick McKee To: jaevans at mail.codenet.net, qrp-l at Lehigh.EDU, fpqrp-l at mpna.com Subject: [147499] Re: homebrewing ultra-lightweight feedline Message-ID: <20030312.181704.8950.1.kc8aon at juno.com> If you have some old foam insulated coax lying around, try using the foam with the shield and center conductor removed, then use a big needle to punch holes throught it the right distance apart and thread them on the wire. To hold it in place, just use a drop of super glue at each junction. This makes a very light weight feedline ! Foam RG59 or foam mini 8 type of coax works very good because the foam insulator is about the right size to work right. 72/73 de: Rick McKee, KC8AON <> Willow Wood, Ohio - Grid: EM88rl SW 40+, HW-8, Yaesu FT-7, Homebrew 6V6 tube TX & Surplus GRC 109 RX Power is for punks ! QRP is for the confident ! QRP-L #2112, FPqrp #33, AR QRP #269 "A clear conscience is most likely the result of a poor memory" On Wed, 12 Mar 2003 10:00:49 -0700 "John_Evans" writes: >greetings, > > I am planning on making some lightweight open feedline for >backpacking. I'll probably use some lengths of teflon wire. > ++++++++++++++++++ Date: Thu, 13 Mar 2003 17:15:11 -0600 From: "Stuart Rohre" To: , Subject: [147568] spacers for homemade ladder line Message-ID: <015a01c2e9b6$657a2aa0$4e100a0a at rohredt2000> John, since you will need to use a transmatch anyway, you do not need to exactly match the spacing of commercial 450 ohm line. The transmatch will take care of it whether closer to 300 ohm or 450 or 600 or 800 etc. With that in mind, there are near 300 ohm spacing plastic spacers that are sold with a couple of nail holes in them, (with the brad nails), for holding down Romex cable. Home Depot chain and others sell them by the bag of 50 or 100 etc. They make good spacers for approximately no. 20 enamel wire which will make a flexible and portable parallel line. (I am still trying to figure out a good use for the nails.) GL and 72, Stuart K5KVH +++++++++++++++++