Re: [Elecraft] [OT] Loss in window line [OPINION] [LONG]
Good discussion as I was thinking to use window line in my new 630m - 40m antenna. Maybe revert to running parallel lines spaced 1-foot with spreaders only at top and bottom of 40-foot vertical run. I did that with my previous inverted-L with no weather related issues. Impedance did shift between summer (unfrozen soil) and winter (frozen) which was easily compensated by a change in loading coil tap. Radials were lying on ground vs in-ground or suspended above ground. New radial field will be planted in the soil a couple inches (so I can mow the lawn without rolling up the radials each time). 73, Ed - KL7UW recent "fun" getting FL-digi to work with my K3. Date: Fri, 14 Jan 2022 13:21:50 -0800 From: Fred Jensen To: Bob McGraw Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] Elecraft Digest, Vol 213, Issue 6 Message-ID: <09a385cb-07b4-29f8-0c64-464705bda...@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed My experience as well.? No real change in loss but the complex impedance at the TX end does change enough to require a re-tune.? It used to be so much simpler when the tank circuit on the PA served as both a matching network and harmonic filter. ? 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] [OT] Loss in window line [OPINION] [LONG]
Al: Nice report. Your paragraph 5 reports on Steve G3TXQ’s (SK) findings …”In G3TXQ’s case…” but also references independent findings by DJ0IP that you do not further describe. Can you add what DJ0IP had to add to this topic such as … “in DJ0IP’s case..” Thanks, Ed McCann AG6CX Sent from my iPhone > On Jan 14, 2022, at 10:01 AM, Al Lorona wrote: > > Whenever somebody mentions "window line" here, one of the first objections > raised is that "when it gets wet, it has very high loss". > > The landmark paper cited is by Wes Stewart, N7WS, which can be found here: > https://www.sadxa.org/n7ws/Ladder_Line.pdf . > > I'm not trying to discredit that paper in any way, but I'd like to point out > two things to keep in mind the next time you hear someone completely and > summarily dismiss window line on the grounds that it has "high loss when > wet", and citing that paper: > > 1. You should note that Wes took measurements at 50 MHz. Window line is > rarely used at that frequency, and anyway the loss has to be extrapolated > back down to the HF region. For instance, if wet window line has a loss of > 5.2 dB at 50 MHz, the loss at 10 MHz is only 2.3 dB and at 3.5 MHz is 1.4 dB. > (See the paper for the equation to extrapolate to another frequency.) 1.4 dB > sounds a heck of a lot better than 5.2, and is on par with 100 feet of the > best coax you can buy. (We are talking only about matched line loss here, and > ignoring additional loss due to SWR.) So that's the first thing. > > 2. Wes's method involved the now legendary use of a "wetting agent" (I assume > soap of some kind) added to the water he sprayed onto his 12-foot sample of > transmission line to simulate rainy conditions on weathered line. To be fair, > Wes himself cautioned that this probably created a worst-case scenario but > judging from other references on the web this wetting agent has been blamed > for excessively inflating the loss to the point of questioning the relevance > of the experiment. DJ0IP and G3TXQ have both claimed that (see > http://www.karinya.net/g3txq/wet_ll/ ). In G3TXQ's case, he was able to > replicate Wes's results by using "a few drops of washing-up liquid" but he > states, "It is not clear whether the high losses associated with using the > wetting agent were due to the more complete wetting of the line or to some > electrical properties of the agent. Nor is it clear how well this test > represents conditions that will be experienced in the 'real world'." > > What's happening to the line when it gets wet, and why should it's > characteristics change at all? To answer this, understand that in balanced > line, the energy is carried in the field between the conductors. Window line > has mostly polyethylene (PE) between the wires which has a dielectric > constant of 2.3, as opposed to air's which is 1.0. Spraying water-- which has > a dielectric constant of 80-- onto PE insulation changes the material > properties between the conductors and, thus, the capacitance. As capacitance > changes, so does everything else: velocity factor, impedance, and loss. One > thing saving us from a catastrophic change in properties is that water tends > to bead up and remain as droplets, and droplets don't like to stay connected > with other droplets. So if you looked at a path perpendicularly across the > surface of the line, you'd see individual, sparse drops rather than a > continuous film of water. > > I couldn't find the dielectric constant of soapy water anywhere on the web -- > but let's assume that the number is close to that of pure water: 80. If you > could somehow give the field a *continuous* path of water from one side to > the other on the window line, you'd have significantly altered the dielectric > constant of the PE; you'd essentially have added a new "path" in "parallel" > with the PE with a dielectric constant some 35 times higher. Although it > would be a very thin layer, it nonetheless could have a significant effect, > as N7WS and G3TXQ have shown. > > We also have an important data point from Bob, K4TAX, showing that the loss > of Bob's window line is pretty much unaffected by rain, although the > electrical length does change. I'll address why this might be later on, but > the point is that this is credible, measured data. Why are these data so > different? > > I did discover that soapy water's pH is above 10 -- possibly as high as 12-- > indicating that there are abundant salts present, probably sodium and/or > potassium. These dissolved salts strongly ionize the water, greatly > increasing its conductivity (and perhaps changing its other electromagnetic > characteristics). On the other hand, rain water is essentially pure, much > closer to distilled water, with relatively few contaminants capable of being > ionized. (See > https://www.waterboards.ca.gov/water_issues/programs/swamp/docs/cwt/guidance/3130en.pdf). > > > Having said all of this, when
Re: [Elecraft] [OT] Loss in window line [OPINION] [LONG]
Al, I don’t disagree with you at all, but I do want to make a comment. After having used coax, “open wire” line, and window line in several locations I think I can add to the discussion. Many folks have antenna tuners that “remember” the L/C combination for “segments” of each band they operate on. Those memories are quite handy when one is moving about the bands - change frequency and the tuner dutifully sets the L/C combination to match what was used the last time at that spot. Unfortunately, there is a big difference in those settings between wet and dry window line. If you’ve “trained” your tuner for a bazillion segments across each ham band in dry conditions, you can rest assured that when it is pouring-ass raining outside those settings go out the window (no pun intended). It is for that reason that, back at my previous QTH in Northern California, I removed 110 feet of window line feeder and replaced it with open wire line on my 88 foot long doublet. I had put the antenna up with window line in the summer and all was fine - until the rainy season started. After the rains started I could forget using the stored memories in my various “auto tuners”. So, yes - window line is OK but be prepared to re “tune” your match when the window line gets wet. I, for one, will not use the stuff again. Jim Bennett / K7TXA Eagle, ID > On Jan 14, 2022, at 11:00 AM, Al Lorona wrote: > > Whenever somebody mentions "window line" here, one of the first objections > raised is that "when it gets wet, it has very high loss". > > The landmark paper cited is by Wes Stewart, N7WS, which can be found here: > https://www.sadxa.org/n7ws/Ladder_Line.pdf . > > I'm not trying to discredit that paper in any way, but I'd like to point out > two things to keep in mind the next time you hear someone completely and > summarily dismiss window line on the grounds that it has "high loss when > wet", and citing that paper: > > 1. You should note that Wes took measurements at 50 MHz. Window line is > rarely used at that frequency, and anyway the loss has to be extrapolated > back down to the HF region. For instance, if wet window line has a loss of > 5.2 dB at 50 MHz, the loss at 10 MHz is only 2.3 dB and at 3.5 MHz is 1.4 dB. > (See the paper for the equation to extrapolate to another frequency.) 1.4 dB > sounds a heck of a lot better than 5.2, and is on par with 100 feet of the > best coax you can buy. (We are talking only about matched line loss here, and > ignoring additional loss due to SWR.) So that's the first thing. > > 2. Wes's method involved the now legendary use of a "wetting agent" (I assume > soap of some kind) added to the water he sprayed onto his 12-foot sample of > transmission line to simulate rainy conditions on weathered line. To be fair, > Wes himself cautioned that this probably created a worst-case scenario but > judging from other references on the web this wetting agent has been blamed > for excessively inflating the loss to the point of questioning the relevance > of the experiment. DJ0IP and G3TXQ have both claimed that (see > http://www.karinya.net/g3txq/wet_ll/ ). In G3TXQ's case, he was able to > replicate Wes's results by using "a few drops of washing-up liquid" but he > states, "It is not clear whether the high losses associated with using the > wetting agent were due to the more complete wetting of the line or to some > electrical properties of the agent. Nor is it clear how well this test > represents conditions that will be experienced in the 'real world'." > > What's happening to the line when it gets wet, and why should it's > characteristics change at all? To answer this, understand that in balanced > line, the energy is carried in the field between the conductors. Window line > has mostly polyethylene (PE) between the wires which has a dielectric > constant of 2.3, as opposed to air's which is 1.0. Spraying water-- which has > a dielectric constant of 80-- onto PE insulation changes the material > properties between the conductors and, thus, the capacitance. As capacitance > changes, so does everything else: velocity factor, impedance, and loss. One > thing saving us from a catastrophic change in properties is that water tends > to bead up and remain as droplets, and droplets don't like to stay connected > with other droplets. So if you looked at a path perpendicularly across the > surface of the line, you'd see individual, sparse drops rather than a > continuous film of water. > > I couldn't find the dielectric constant of soapy water anywhere on the web -- > but let's assume that the number is close to that of pure water: 80. If you > could somehow give the field a *continuous* path of water from one side to > the other on the window line, you'd have significantly altered the dielectric > constant of the PE; you'd essentially have added a new "path" in "parallel" > with the PE with a dielectric constant some 35 times higher.
Re: [Elecraft] [OT] Loss in window line [OPINION] [LONG]
I concur with the conclusion that water has little effect on window line. I base this on my own experience using window line for years. I always feed it into a tuner and, if water has any effect on the line, I have to adjust the settings of the tuner. It is only necessary to adjust the tuner under very heavy rain. Anything resembling a normal amount of water on the line has essentially no effect, even after years of dirt buildup. Years ago, when I had a swimming pool, I spanned the pool with a length of underwater ladder line and made some simple measurements that indicated only a nominal change. And pool water is purposely chlorinated, which increases the conductivity, although I don't know by how much. 73 de dave ab9ca Sent from my iPhone > On Jan 14, 2022, at 11:00, Al Lorona wrote: > > Whenever somebody mentions "window line" here, one of the first objections > raised is that "when it gets wet, it has very high loss". > > The landmark paper cited is by Wes Stewart, N7WS, which can be found here: > https://www.sadxa.org/n7ws/Ladder_Line.pdf . > > I'm not trying to discredit that paper in any way, but I'd like to point out > two things to keep in mind the next time you hear someone completely and > summarily dismiss window line on the grounds that it has "high loss when > wet", and citing that paper: > > 1. You should note that Wes took measurements at 50 MHz. Window line is > rarely used at that frequency, and anyway the loss has to be extrapolated > back down to the HF region. For instance, if wet window line has a loss of > 5.2 dB at 50 MHz, the loss at 10 MHz is only 2.3 dB and at 3.5 MHz is 1.4 dB. > (See the paper for the equation to extrapolate to another frequency.) 1.4 dB > sounds a heck of a lot better than 5.2, and is on par with 100 feet of the > best coax you can buy. (We are talking only about matched line loss here, and > ignoring additional loss due to SWR.) So that's the first thing. > > 2. Wes's method involved the now legendary use of a "wetting agent" (I assume > soap of some kind) added to the water he sprayed onto his 12-foot sample of > transmission line to simulate rainy conditions on weathered line. To be fair, > Wes himself cautioned that this probably created a worst-case scenario but > judging from other references on the web this wetting agent has been blamed > for excessively inflating the loss to the point of questioning the relevance > of the experiment. DJ0IP and G3TXQ have both claimed that (see > http://www.karinya.net/g3txq/wet_ll/ ). In G3TXQ's case, he was able to > replicate Wes's results by using "a few drops of washing-up liquid" but he > states, "It is not clear whether the high losses associated with using the > wetting agent were due to the more complete wetting of the line or to some > electrical properties of the agent. Nor is it clear how well this test > represents conditions that will be experienced in the 'real world'." > > What's happening to the line when it gets wet, and why should it's > characteristics change at all? To answer this, understand that in balanced > line, the energy is carried in the field between the conductors. Window line > has mostly polyethylene (PE) between the wires which has a dielectric > constant of 2.3, as opposed to air's which is 1.0. Spraying water-- which has > a dielectric constant of 80-- onto PE insulation changes the material > properties between the conductors and, thus, the capacitance. As capacitance > changes, so does everything else: velocity factor, impedance, and loss. One > thing saving us from a catastrophic change in properties is that water tends > to bead up and remain as droplets, and droplets don't like to stay connected > with other droplets. So if you looked at a path perpendicularly across the > surface of the line, you'd see individual, sparse drops rather than a > continuous film of water. > > I couldn't find the dielectric constant of soapy water anywhere on the web -- > but let's assume that the number is close to that of pure water: 80. If you > could somehow give the field a *continuous* path of water from one side to > the other on the window line, you'd have significantly altered the dielectric > constant of the PE; you'd essentially have added a new "path" in "parallel" > with the PE with a dielectric constant some 35 times higher. Although it > would be a very thin layer, it nonetheless could have a significant effect, > as N7WS and G3TXQ have shown. > > We also have an important data point from Bob, K4TAX, showing that the loss > of Bob's window line is pretty much unaffected by rain, although the > electrical length does change. I'll address why this might be later on, but > the point is that this is credible, measured data. Why are these data so > different? > > I did discover that soapy water's pH is above 10 -- possibly as high as 12-- > indicating that there are abundant salts present, probably sodium
[Elecraft] [OT] Loss in window line [OPINION] [LONG]
Whenever somebody mentions "window line" here, one of the first objections raised is that "when it gets wet, it has very high loss". The landmark paper cited is by Wes Stewart, N7WS, which can be found here: https://www.sadxa.org/n7ws/Ladder_Line.pdf . I'm not trying to discredit that paper in any way, but I'd like to point out two things to keep in mind the next time you hear someone completely and summarily dismiss window line on the grounds that it has "high loss when wet", and citing that paper: 1. You should note that Wes took measurements at 50 MHz. Window line is rarely used at that frequency, and anyway the loss has to be extrapolated back down to the HF region. For instance, if wet window line has a loss of 5.2 dB at 50 MHz, the loss at 10 MHz is only 2.3 dB and at 3.5 MHz is 1.4 dB. (See the paper for the equation to extrapolate to another frequency.) 1.4 dB sounds a heck of a lot better than 5.2, and is on par with 100 feet of the best coax you can buy. (We are talking only about matched line loss here, and ignoring additional loss due to SWR.) So that's the first thing. 2. Wes's method involved the now legendary use of a "wetting agent" (I assume soap of some kind) added to the water he sprayed onto his 12-foot sample of transmission line to simulate rainy conditions on weathered line. To be fair, Wes himself cautioned that this probably created a worst-case scenario but judging from other references on the web this wetting agent has been blamed for excessively inflating the loss to the point of questioning the relevance of the experiment. DJ0IP and G3TXQ have both claimed that (see http://www.karinya.net/g3txq/wet_ll/ ). In G3TXQ's case, he was able to replicate Wes's results by using "a few drops of washing-up liquid" but he states, "It is not clear whether the high losses associated with using the wetting agent were due to the more complete wetting of the line or to some electrical properties of the agent. Nor is it clear how well this test represents conditions that will be experienced in the 'real world'." What's happening to the line when it gets wet, and why should it's characteristics change at all? To answer this, understand that in balanced line, the energy is carried in the field between the conductors. Window line has mostly polyethylene (PE) between the wires which has a dielectric constant of 2.3, as opposed to air's which is 1.0. Spraying water-- which has a dielectric constant of 80-- onto PE insulation changes the material properties between the conductors and, thus, the capacitance. As capacitance changes, so does everything else: velocity factor, impedance, and loss. One thing saving us from a catastrophic change in properties is that water tends to bead up and remain as droplets, and droplets don't like to stay connected with other droplets. So if you looked at a path perpendicularly across the surface of the line, you'd see individual, sparse drops rather than a continuous film of water. I couldn't find the dielectric constant of soapy water anywhere on the web -- but let's assume that the number is close to that of pure water: 80. If you could somehow give the field a *continuous* path of water from one side to the other on the window line, you'd have significantly altered the dielectric constant of the PE; you'd essentially have added a new "path" in "parallel" with the PE with a dielectric constant some 35 times higher. Although it would be a very thin layer, it nonetheless could have a significant effect, as N7WS and G3TXQ have shown. We also have an important data point from Bob, K4TAX, showing that the loss of Bob's window line is pretty much unaffected by rain, although the electrical length does change. I'll address why this might be later on, but the point is that this is credible, measured data. Why are these data so different? I did discover that soapy water's pH is above 10 -- possibly as high as 12-- indicating that there are abundant salts present, probably sodium and/or potassium. These dissolved salts strongly ionize the water, greatly increasing its conductivity (and perhaps changing its other electromagnetic characteristics). On the other hand, rain water is essentially pure, much closer to distilled water, with relatively few contaminants capable of being ionized. (See https://www.waterboards.ca.gov/water_issues/programs/swamp/docs/cwt/guidance/3130en.pdf). Having said all of this, when you study the G3TXQ paper I mentioned earlier, there's a glaring data point: Steve measured nearly constant, high loss, using soapy water, *from 7 through 30 MHz*. This confirms that an effect of the soap is swamping out everything else. In other words, there's something *in the soap itself* that is skewing the measurements beyond its intended purpose. He just wanted the soap to make the water cling better, but it ended up perturbing the very thing he was trying to measure (loss) way too much. It's a
