Re: Topband: HFTA, Radio Arcala, general comments
> I was regretful enough after installing a tall tower and using wire > antennas. At one point I had a two element wire dipole phased array up at > maybe 250-260 feet. When it fell down in an ice storm, I was relieved I > didn't have to take it down. I had a 110' Aluminum Heights fold over had a 10, 15 & 20, 5 element KLM monobanders on top. It was raised and lowered by a hand cranked winch. The fulcrum/pulley arrangement was at 24' I was lowering it one day and the cable kinked at the winch when it was bent 20 degrees. No way to climb to the top and get a rope up to the top to pull it back upright. I did everything I could to undo the kink and then... it snapped. I wass watching while that beautiful tower landed flat 7 I saw something I never saw before, there was a ripple that went across my lawn, the neighbors lawn and out as far as I could see, lasted maybe 2 seconds before it was gone. Just like dropping a rock in a still pond, only one impulse . Bad day but it's interesting the things that happen that you don't think of when a tower comes down. Thank God for Insurance... Sure wish I had that tower today. Now all I have are wires hanging on trees. Gary KA1J ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
My 160 aerial next season may be a top loaded vert that can be laid over from the base. After fiddling with an "L" at 64N latitude, I'm curious about which portion of the L is best as propagation and angles (?) vary. Our ionospheric world is different. We can hear the Aurora and it's effects...from quiet to loud background QRN as conditions change during absorption events. It's audible on vertically firing horizontal loops especially with an on-ground reflector. I'd like to see if altering the vert's angle has any effect. It may not, but ??? 73, Gary NL7Y > Guys, I am probably completely off the wall here. But given all the talk > about a 300 foot vertical not working well on 160 and a very high dipole not > working well on 160 leads me to a very unscientific "conclusion" or a > possible real hypothesis.. That super low angle radiation is NOT a good > thing for 160. "SNIP" > Mike AB7ZU > ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Dang Tom. I just sent out a more wordy version of what you just said. This is getting strange. Not sure why it hasn't been disseminated yet (my email), but I swear I sent it just moments before your email hit my system. You just added some fuel to my fire. Short version: I, with my rather inexperienced eye (160 experience, that is) is seeing a pattern that seems to indicate what we would call low radiation angles aren't really optimum for long range 160 communications. The other email goes into a little more detail in why I am thinking this way. Morning enhancement, especially with high angle radiators (like mine) where I am working Japan and Chile on a radiator that can very truthfully be called an NVIS antenna. On higher frequencies, a scaled version of my antenna wouldn't radiate a signal out of the southwest region, much less thousands of miles distant. Just a thought! Again, my other email expounds a little more, but this was the conclusion in a nutshell. Maybe "low horizontal" antennas really ARE better on 160 than they should be. Given our experience with low antennas on the higher bands, it seems counter-intuitive. But there it is. Mike AB7ZU Kuhi no ka lima, hele no ka maka On Oct 24, 2012, at 17:12, "Tom W8JI" wrote: >> If we knew those, then we could calculate the location and distance of the >> signal hops. That might give us some insight as to why some people have >> found a taller monopole to be worse than a shorter one at a given distance. > > Back in the 70's or 80's there was speculation a low angle was lossy from > grazing along, based on others having poor experiences with taller verticals. > The top of my tall tower had some antennas and side arms which top loaded it > a bit, but not much. Certainly the wave refracts gradually at a minimum, and > so I think distance would not tell anyone much. There have been a host of > theories since the 1960's, even some from Stew the real W1BB. :-) > > I don't know what happens when it gets up in the soup, although people like > K9LA should be pretty well versed on it. I only know things behave > differently all the time, and what antenna generally works most of the time. > > For example, at sunrise most of the time almost anything reasonably efficient > works about the same here. It's more a matter of ERP at any not-too-low angle > and any polarization. > > 73 Tom > ___ > Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Topband: HFTA 160 Elevation Statistics
I just double checked my HFTA software, and it does present a set of elevation angle statistics for 1.8MHZ that are significantly different than the statistics it shows for 3.5MHZ. Not sure how these are derived. 73 Charlie N8RR ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Guys, I am probably completely off the wall here. But given all the talk about a 300 foot vertical not working well on 160 and a very high dipole not working well on 160 leads me to a very unscientific "conclusion" or a possible real hypothesis.. That super low angle radiation is NOT a good thing for 160. Given the other anomalous behaviors of 160, like the early morning enhancements and that antennas with a major high angle component and a relatively minor low angle radiation component seem to do quite well on 160.. 80 meters, too, for that matter. That certainly isn't all of the low band anomalies, but these are a couple we all have certainly experienced. Given these and others, I am tending to think that the quest for really low angles of radiation is counterproductive.. and not so surprisingly, counter-intuitive, as well. There is, obviously, a "sweet spot" for lower angle radiation on 160. Additionally, I am beginning to think that it is as unique as the band itself. For example, higher bands seem to favor the lowest possible radiation angle that can be produced.. Could it be that 160 "prefers" something closer to, let's say 45 degrees? Not meaning that 45 actually IS that magic number, but maybe close to it Closer, anyway, than a 5 degree angle? Just a thought. No basis in hard data, but these general anomalies (now THERE is an oxymoron if there ever was on) seem to be piling up. to these untrained eyes, anyway. Mike AB7ZU Kuhi no ka lima, hele no ka maka On Oct 24, 2012, at 12:09, "Tom W8JI" wrote: >> Just to point out that we don't have measurements of arrival angles at the >> ionosphere proving the fields shown in a NEC far-field analysis, either. Yet >> people seem to accept a NEC far-field pattern as gospel, even though it does >> not accurately show the radiation launched by a monopole at elevation angles >> below 10 degrees or so. > > We have a lot of things we claim as fact, even though we don't supporting > data. Some border on magic. > > That's why I A-B test things for several months before deciding anything. > > :-) > > I installed a 300 foot tower because I remembered how well a dipole at 300 > feet worked at a BC station. I was sure, based on the DX contacts, the dipole > was a killer antenna for receiving and transmitting. Problem is when I > finally installed that wonderful antenna after all that work, my vertical > tied broadside to the dipole and badly beat the dipole off the dipole ends. > > 73 Tom > ___ > Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: HFTA, Radio Arcala, general comments
As I recall they never blew up the receiver here, unlike TF4M, GM3POI, and others in that direction from KL7 who were consistently available during times of low absorption over the N Pole. Then again, who knows what antenna array they were using or the ERP when heard. I'd still like to know their A/B results as there's something to be learned from all that hard work. 73, Gary NL7Y > How strong of a signal can that enormous Yagi radiate into the USA on 160? > I have never heard them. > > 73, Mike > www.w0btu.com > ___ Topband reflector - topband@contesting.com
Re: Topband: HFTA, Radio Arcala, general comments
My comments?follow on three topics that have been brought up, ? HFTA - It can import?the elevation angle files generated from IONCAP/VOACAP that Dean N6BV produced. HFTA?does not have an ionospheric module in it. And > yes, the files only go down to?80m because of IONCAP/VOACAP limitations. ? Radio Arcala - I have always believed that a horizontal antenna on 160m at very high latitudes would?generally be worse (note that I didn't say always)?than a vertical due to the effect of the Earth's magnetic field. How?"theory" translates to "the real world" is always subject to careful consideration, but I've seen enough data in the technical literature to stand by my belief. ? Propagation on 160m - This is a very difficult topic. Most of what makes 160m go is down at D region and E region altitudes, and it is very tough to gather data on these regions at night. What data we have is mostly from rocket flights and scatter radar - which gives us a model that probably doesn't capture all the? variability.?And I don't think we know all the mechanisms yet that give us good propagation versus bad propagation. ? Carl K9LA Bob Brown NM7M (SK) wrote lots about propagation being quite a bit different on 160 and MF because the ionosphere does not interact with the waves in the same way it does at HF. The electron gyrofrequency (I just *love* saying "gyrofrequency", don't you?) in the lower layers (what Carl is referring to above) is much closer to 1.8 MHz and causes the wave coupling to change dramatically in ways that are not well understood. This changes with latitude and time of day (or night). There were a number of articles by Bob about "ducts" between the layers that were very dependent on wave launch angle to get into them. Such effects lead to odd propagation like the frequently observed "spotlight" propagation and the high-angle antennas hearing and working DX signals when low-angle would seem to be what "should" work better. My point is that applying models of ionospheric propagation that work at HF, even 80 meters, often have a lot of trouble at lower frequencies because the physics are different at those frequencies. That means you might need a different approach to antenna system design than you would find successful at higher frequencies. Things like improving system efficiency give the same benefits but the most desirable antenna radiation pattern may not be what you expect. Consequently, this is an area in which amateurs truly can push the state of the art. 73, Ward N0AX ___ Topband reflector - topband@contesting.com
Re: Topband: HFTA, Radio Arcala, general comments
Radio Arcala - I have always believed that a horizontal antenna on 160m at very high latitudes would generally be worse (note that I didn't say always) than a vertical due to the effect of the Earth's magnetic field. How "theory" translates to "the real world" is always subject to careful consideration, but I've seen enough data in the technical literature to stand by my belief. I think before I spent money like that, assuming I had the money, I would have asked around or maybe tried a simple high dipole for several weeks in comparison to a vertical. I was regretful enough after installing a tall tower and using wire antennas. At one point I had a two element wire dipole phased array up at maybe 250-260 feet. When it fell down in an ice storm, I was relieved I didn't have to take it down. All of that was based on my memory of how well a dipole worked on a ~350 ft tower. A few good signal reports corrupted my objectivity. :-) 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: HFTA, Radio Arcala, general comments
How strong of a signal can that enormous Yagi radiate into the USA on 160? I have never heard them. 73, Mike www.w0btu.com On Wed, Oct 24, 2012 at 7:23 PM, k...@frontier.com wrote: > > Radio Arcala - I have always believed that a horizontal antenna on 160m at > very high latitudes would generally be worse (note that I didn't say > always) than a vertical due to the effect of the Earth's magnetic field. > How "theory" translates to "the real world" is always subject to careful > consideration > ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Paul, W9AC said:
Topband: HFTA, Radio Arcala, general comments
My comments follow on three topics that have been brought up, HFTA - It can import the elevation angle files generated from IONCAP/VOACAP that Dean N6BV produced. HFTA does not have an ionospheric module in it. And yes, the files only go down to 80m because of IONCAP/VOACAP limitations. Radio Arcala - I have always believed that a horizontal antenna on 160m at very high latitudes would generally be worse (note that I didn't say always) than a vertical due to the effect of the Earth's magnetic field. How "theory" translates to "the real world" is always subject to careful consideration, but I've seen enough data in the technical literature to stand by my belief. Propagation on 160m - This is a very difficult topic. Most of what makes 160m go is down at D region and E region altitudes, and it is very tough to gather data on these regions at night. What data we have is mostly from rocket flights and scatter radar - which gives us a model that probably doesn't capture all the variability. And I don't think we know all the mechanisms yet that give us good propagation versus bad propagation. Carl K9LA. ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Herb's experience below echoes mine at my house here in GA and at BC stations in the Midwest. Others besides Herb have reported the same. - Original Message - From: "Herb Schoenbohm" To: Sent: Wednesday, October 24, 2012 6:58 PM Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity I used or tried to use a 308 foot self supporting base insulated Blau-Knox in the late 70's and early 80's (Picture on QRZ.com) and although I could not do A-B tests I found it horrible and that was over a 2 degree buried 260 foot radial ground system for 970Khz right next to the ocean. I found better use for it by using it to run a rope up to the top and hung 1/2 wave slopers down to the sea, and that was much better for RX reports on 160 from Europe. I really expected better results but was amazed at the difference over many years of testing. I would drop the sloper(s) to the ground when trying to use the 308 foot free standing tower...which the books said would be an optimal low angle radiator. The slopers and even a full sized corner fed delta loop were always much better. Herb, KV4FZ On 10/24/2012 5:44 PM, Tom W8JI wrote: Did you --or anyone else you are aware of-- ever A-B test a ~120' tower against a ~300' tower on 160? I A-B or A-B-C tested several antennas, including a low dipole, the high dipole, an element from my four square, a ~318 foot insulated tower vertical, and I think my tall omni vertical was about 190 feet at that time. The tall vertical tower was definitely worse compared to shorter verticals, and had almost no short skip signal around Georgia. I had isolation chokes for lights and a base insulator, but that 300+ foot tower was so poor I never used it as a vertical. By the way, to show how bad interaction is, I had to detune unused towers even when they were 300 feet or so apart. If you recall W8LT and the balloon verticals, they didn't do so well with that antenna at 5/8th wave. I used WSPD, WOHO, and WXEZ (King Road 350 ft) towers also, but had no A-B tests. Anything tall or new received good reports, if I told the other person it was tall or new. This is a common result, similar to the well-known G5RV effects. Pick an unpopular antenna like a G5RV and say you are using it in a test, and even if you do not actually switch antennas the G5RV will get a weaker report over long averages of tests. You can see a similar effect with guest operators and a no-change switch position. They always like the better antenna, even when it is the same antenna. :-) To avoid the G5RV effect when making A-B tests, I never said which antenna was actually A or B. I also would randomly change A or B around in different tests. Just watching reports without changing antennas at all is interesting. 73 Tom ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Maybe I just abused/misused the term "takeoff angle" myself. :-) 73, Mike www.w0btu.com On Wed, Oct 24, 2012 at 7:13 PM, Tom W8JI wrote: > What is your (or anybody's) definition/understanding of the term "takeoff >> angle?" >> > > Take off angle is the thing the fellow who wrote EZNEC wished no one used > because he knew it would get abused and misused, but since someone else > started with it he included it. > > :-) > ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
What is your (or anybody's) definition/understanding of the term "takeoff angle?" Take off angle is the thing the fellow who wrote EZNEC wished no one used because he knew it would get abused and misused, but since someone else started with it he included it. :-) ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
If we knew those, then we could calculate the location and distance of the signal hops. That might give us some insight as to why some people have found a taller monopole to be worse than a shorter one at a given distance. Back in the 70's or 80's there was speculation a low angle was lossy from grazing along, based on others having poor experiences with taller verticals. The top of my tall tower had some antennas and side arms which top loaded it a bit, but not much. Certainly the wave refracts gradually at a minimum, and so I think distance would not tell anyone much. There have been a host of theories since the 1960's, even some from Stew the real W1BB. :-) I don't know what happens when it gets up in the soup, although people like K9LA should be pretty well versed on it. I only know things behave differently all the time, and what antenna generally works most of the time. For example, at sunrise most of the time almost anything reasonably efficient works about the same here. It's more a matter of ERP at any not-too-low angle and any polarization. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Mike wrote: We know the radius of the earth and have a good idea of the takeoff angle from a given monopole height. (etc) What is your (or anybody's) definition/understanding of the term "takeoff angle?" R. Fry ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
We know the radius of the earth and have a good idea of the takeoff angle from a given monopole height. The unknown variable (to me, anyway) is the approximate height of the reflecting layer in the ionosphere that affects 160m. I'm guessing that's not a constant by any means. If we knew those, then we could calculate the location and distance of the signal hops. That might give us some insight as to why some people have found a taller monopole to be worse than a shorter one at a given distance. 73, Mike www.w0btu.com On Wed, Oct 24, 2012 at 6:33 PM, Richard Fry wrote: > ... a longer monopole (up to 5/8WL) would provide better groundwave fields > and low-angle fields .. > ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
The tall vertical tower was definitely worse compared to shorter verticals, and had almost no short skip signal around Georgia. I had isolation chokes for lights and a base insulator, but that 300+ foot tower was so poor I never used it as a vertical. Not sure what frequency this comment applies to. But a 300-ft tower would be about 197 degrees in physical height on 160m, and its elevation pattern would be close to the pattern for the 195-degree monopole shown in the plots linked below. The short skip being sought might better have been provided by a shorter monopole, but a longer monopole (up to 5/8WL) would provide better groundwave fields and low-angle fields, even with the ~poor earth conductivities in some parts of Georgia. http://i62.photobucket.com/albums/h85/rfry-100/MWElPatComparison.jpg R. Fry ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
On 10/24/2012 06:37 PM, Mike Waters wrote: So according to your tests, the ~5/8 wave tower was always inferior to the 190' tower, no matter what the distance was? That is very interesting, And I have little doubt all your towers had sufficient radials under them. :-) What do you think about 120' vs 190' ? Ever do any tests like that? I wonder if it would be an idea to try these ideas on 40m. That way it could be tested with much antennas small enough multiple people might be willing to set them up for testing. ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
I used or tried to use a 308 foot self supporting base insulated Blau-Knox in the late 70's and early 80's (Picture on QRZ.com) and although I could not do A-B tests I found it horrible and that was over a 2 degree buried 260 foot radial ground system for 970Khz right next to the ocean. I found better use for it by using it to run a rope up to the top and hung 1/2 wave slopers down to the sea, and that was much better for RX reports on 160 from Europe. I really expected better results but was amazed at the difference over many years of testing. I would drop the sloper(s) to the ground when trying to use the 308 foot free standing tower...which the books said would be an optimal low angle radiator. The slopers and even a full sized corner fed delta loop were always much better. Herb, KV4FZ On 10/24/2012 5:44 PM, Tom W8JI wrote: Did you --or anyone else you are aware of-- ever A-B test a ~120' tower against a ~300' tower on 160? I A-B or A-B-C tested several antennas, including a low dipole, the high dipole, an element from my four square, a ~318 foot insulated tower vertical, and I think my tall omni vertical was about 190 feet at that time. The tall vertical tower was definitely worse compared to shorter verticals, and had almost no short skip signal around Georgia. I had isolation chokes for lights and a base insulator, but that 300+ foot tower was so poor I never used it as a vertical. By the way, to show how bad interaction is, I had to detune unused towers even when they were 300 feet or so apart. If you recall W8LT and the balloon verticals, they didn't do so well with that antenna at 5/8th wave. I used WSPD, WOHO, and WXEZ (King Road 350 ft) towers also, but had no A-B tests. Anything tall or new received good reports, if I told the other person it was tall or new. This is a common result, similar to the well-known G5RV effects. Pick an unpopular antenna like a G5RV and say you are using it in a test, and even if you do not actually switch antennas the G5RV will get a weaker report over long averages of tests. You can see a similar effect with guest operators and a no-change switch position. They always like the better antenna, even when it is the same antenna. :-) To avoid the G5RV effect when making A-B tests, I never said which antenna was actually A or B. I also would randomly change A or B around in different tests. Just watching reports without changing antennas at all is interesting. 73 Tom ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
I didn't remember W8LT's 5/8 wave balloon verticals. But I do recall your telling me about your neighbor's inverted-L nearly always being about the same strength as your old 120' tower in Ohio on 160. Do you recall how high the vertical portion of his inverted-L was? So according to your tests, the ~5/8 wave tower was always inferior to the 190' tower, no matter what the distance was? That is very interesting, And I have little doubt all your towers had sufficient radials under them. :-) What do you think about 120' vs 190' ? Ever do any tests like that? 73, Mike www.w0btu.com On Wed, Oct 24, 2012 at 4:44 PM, Tom W8JI wrote: > Did you --or anyone else you are aware of-- ever A-B test a ~120' tower >> against a ~300' tower on 160? >> > > I A-B or A-B-C tested several antennas, including a low dipole, the high > dipole, an element from my four square, a ~318 foot insulated tower > vertical, and I think my tall omni vertical was about 190 feet at that time. > > The tall vertical tower was definitely worse compared to shorter > verticals, and had almost no short skip signal around Georgia. I had > isolation chokes for lights and a base insulator, but that 300+ foot tower > was so poor I never used it as a vertical. > 73 Tom > ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Guy Olinger wrote: I have not personally seen work to validate signal strength and prove the mechanics of arrival at various altitudes at 50 km. ... NEC4 says that it doesn't continue. But NEC4 also nicely predicts the 2.8 km helicopter measurements. This depends totally on the accuracy of the NEC model, and the analysis that the NEC operator asks NEC to perform -- which depends on the background, skill and experience of said operator. A NEC far-field plot shows zero relative field (E/Emax) in the horizontal plane, and not much more at low elevation angles above it. A plot close to the radiator that includes the surface wave shows that radiation from a monopole is maximum in the horizontal plane, and not much less than that for low elevation angles above it -- which low-angle fields, in reality, are space waves. There is nothing in physics that would preclude those low-angle fields from propagation on to the ionosphere. There apparently is completely zilch commercial interest or need for the answers to our speculations. Not so, sorry. Class A (50 kW, non-directional, 24/7) AM broadcast stations depend on this low-angle radiation to produce their large coverage area footprints, at night. This low-angle radiation is equally important to hams, but apparently is not recognized by most of them. In my college days at Berea, Ky, I would listen at night to clear channel 650 WSM in Nashville (Grand Ole Opry, etc), using a 195 degree tower, supposedly the Cadillac for low angle transmission. In the daytime at a distance of 165 miles, the 50 kW signal was there but very raspy to the point of irritation at Berea. I learned not to bother turning on that station during day. No surprise, there, especially if you were using a Zenith all-American five in a dorm room. Probably a good car radio even a bit beyond Berea, KY would/does receive a noticeably better daytime signal from WSM than you report. The WSM daytime signal in Berea at 165 miles would be groundwave, which for those conditions will be relatively weak. The WSM nighttime signal in/near Berea would be mainly skywave, which might average more than 10X greater fields than their day/night groundwave there. R. Fry ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
I A-B or A-B-C tested several antennas, including a low dipole, the high dipole, an element from my four square, a ~318 foot insulated tower vertical, and I think my tall omni vertical was about 190 feet at that time. The tall vertical tower was definitely worse compared to shorter verticals, and had almost no short skip signal around Georgia. I had isolation chokes for lights and a base insulator, but that 300+ foot tower was so poor I never used it as a vertical. That may have been confusing. I never got in the habit of calling my 300ft + insulated tower a tall vertical, because I always considered it a support. It did have isolation chokes for cables and lights and a base insulator. It worked its way up in height from doing radial tests until it eventually reached ~318 feet. The vertical I call a tall vertical has always been a 180-200 ft insulated vertical, so it is not really the tallest vertical. It was just the one that worked best as a tall vertical. The really tall tower was so poor for overall use I just grounded the base when I rebuilt it with Rohn 65G a few years ago, so now it is no longer available as a series-fed structure. It has a ground system around it that allows other test antennas, and for a while I had two four squares. Since the 300 ft gets hit by lightning at least once in every storm, it is too much trouble to have cables run out to a four square with ground radials. Lightning current melted an LMR400 cable shield every other storm. ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Did you --or anyone else you are aware of-- ever A-B test a ~120' tower against a ~300' tower on 160? I A-B or A-B-C tested several antennas, including a low dipole, the high dipole, an element from my four square, a ~318 foot insulated tower vertical, and I think my tall omni vertical was about 190 feet at that time. The tall vertical tower was definitely worse compared to shorter verticals, and had almost no short skip signal around Georgia. I had isolation chokes for lights and a base insulator, but that 300+ foot tower was so poor I never used it as a vertical. By the way, to show how bad interaction is, I had to detune unused towers even when they were 300 feet or so apart. If you recall W8LT and the balloon verticals, they didn't do so well with that antenna at 5/8th wave. I used WSPD, WOHO, and WXEZ (King Road 350 ft) towers also, but had no A-B tests. Anything tall or new received good reports, if I told the other person it was tall or new. This is a common result, similar to the well-known G5RV effects. Pick an unpopular antenna like a G5RV and say you are using it in a test, and even if you do not actually switch antennas the G5RV will get a weaker report over long averages of tests. You can see a similar effect with guest operators and a no-change switch position. They always like the better antenna, even when it is the same antenna. :-) To avoid the G5RV effect when making A-B tests, I never said which antenna was actually A or B. I also would randomly change A or B around in different tests. Just watching reports without changing antennas at all is interesting. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Tom, Did you --or anyone else you are aware of-- ever A-B test a ~120' tower against a ~300' tower on 160? 73, Mike www.w0btu.com On Wed, Oct 24, 2012 at 2:09 PM, Tom W8JI wrote: > That's why I A-B test things for several months before deciding anything. > ... I installed a 300 foot tower ... > ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
I have not personally seen work to validate signal strength and prove the mechanics of arrival at various altitudes at 50 km. Tons of speculation, extrapolation. NEC4 says that it doesn't continue. But NEC4 also nicely predicts the 2.8 km helicopter measurements. There apparently is completely zilch commercial interest or need for the answers to our speculations. The question is in a niche within 160m operation, itself a niche within ham radio, which is yet a niche within general radio. PLUS our propensity to want things for free, is it really any amazement that the issue is not researched? In my college days at Berea, Ky, I would listen at night to clear channel 650 WSM in Nashville (Grand Ole Opry, etc), using a 195 degree tower, supposedly the Cadillac for low angle transmission. In the daytime at a distance of 165 miles, the 50 kW signal was there but very raspy to the point of irritation at Berea. I learned not to bother turning on that station during day. Complaints. Some folks in the dorm had the same response to scratchy radio signals as drawing fingernails across a chalkboard. At night the combination of a strong, clear WSM, live broadcasts, and a wonderfully mellow 5 tube Zenith in a bakelite cabinet was a near constant sound in that end of the hall. I'm sure that WSM was happy to cover a radius most of the way to Knoxville in the daytime. At night they had a killer signal without any background noise. I would hear fading as the signal started to come up at dusk, but nighttime fading would have been from extremely loud to very loud, because I never heard any. So I would have to say that whatever passed for ground wave on that signal was pure useless for DX in ham terms. "Ground enhanced" or "ground ducted" , or whatever you would want to call that, should be the same day or night, right? It was HUGELY attenuated from the night time sky wave. So far, regarding this issue, I have seen/heard neither technical measurement nor anecdote to contradict the NEC4 estimations. I have other issues with NEC4, but none related to this. Yet. Anybody know someone who owns a helicopter just looking for any excuse to fly on a nice day? It is possible to stack up graphs, equations, and quotes from old textbooks until the BS buffer completely overflows all over the rug. But until we have sitting-man-with-meter-in-helicopter out at 50 km drop from operational ceiling to the ground, measuring all the while, all we have is anecdotes that follow NEC4, and no contradictions at all from technically proper measurements. 73, Guy. On Wed, Oct 24, 2012 at 9:56 AM, Paul Christensen wrote: > I have linked to an image of a NEC 4 vertical profile analysis of the > WLS-AM radiator. As most everyone here knows, WLS is a legendary 50KW AM > station in Chicago. WLS uses a 190 degree radiator and is the preferred > antenna height for most AMBC purposes since it's the height that produces > the most gain at zero elevation while simultaneously minimizing skywave > lobes. > > http://tinyurl.com/9zuqpre > > Notice how the pattern is crushed to the horizon with very little of a > high angle lobe produced.I ran a far-field analysis of three > hypothetical models over: (1) average soil conductivity [green]; (2) poor > soil conductivity [red]; and (3) highly conductive salt water [blue]. > Notice a few things from the colored overlay: > > 1) The WLS radiator over salt water produces a significantly improved > field strength at a distance of 1km over the other two models. No surprise > here; > 2) The shape of the far-field profiles *appear* to change as a function of > ground conductivity. > > However, if we were able to conduct a surface wave analysis and overlay > the three curves (4Nec2 does not appear to allow that in the surface mode, > but I'll check with the author), we would find that the shape of the curves > going up in Z axis vertical distance is the same. I've run the model for > many vertical radiators and that's what NEC 4 reports. This too should be > no surprise as ground wave effects to 3 MHz have been extensively > documented in academia since the 1930s. > > Here again, if we were to believe that WLS produces no far field strength > at low elevation over anything but salt water, they would have very limited > daytime listeners - even with 50KW of output power. So, to Rich's past > points, we need to consider both the far field and surface wave components > when computing far field strength over a range of elevations. Don't just > believe that the far field plots we've seen time and again are always > representative of the actual low-angle field strength. According to Jerry > Burke, author of NEC 4, the surface wave component can be a major part of > achieving ionospheric DX reach through at least 3 MHz. > > Paul, W9AC > > - Original Message - From: "Richard Fry" > To: > Sent: Tuesday, October 23, 2012 9:28 AM > Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
How has the vert/4-SQ vs Yagi performed? A dipole and a vertical are a better test, because a four square traditionally has more losses and different gain than a Yagi. It would be interesting to see how that big Yagi works, but gain should be measured over a dipolenot a different polarization array. ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Have the folks at Radio Arcala OH8X learned something about 160M antennas and propagation? How has the vert/4-SQ vs Yagi performed? 73, Gary NL7Y ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Hi Paul, I think the important "take away" in these discussions is that the far field pattern alone is not enough to show the real vertical profile from a vertical monopole. The significance of the ionospheric element is another issue altogether. Don't all of us on 160 know that! Making things worse, we more often than not firmly validate system changes with the worse type of testing. 73 tom ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Tom, As I recall, HFTA software has an ionospheric module that calculates the predictability of arrival angle as a function of frequency, time of day, season, etc. Learning that program has been on my "to do" list for a long time. Perhaps others here can comment on whether the arrival angle information goes down to 160m in that program. I believe the program was designed for elevated antennas and hence the need to analyze terrain. So, in addition to 160m relevance, I'm not sure it applies to base-fed monopoles. I think the important "take away" in these discussions is that the far field pattern alone is not enough to show the real vertical profile from a vertical monopole. The significance of the ionospheric element is another issue altogether. Paul, W9AC - Original Message - From: "Tom W8JI" To: "Richard Fry" ; Sent: Wednesday, October 24, 2012 2:39 PM Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity - Original Message - From: "Richard Fry" To: Sent: Wednesday, October 24, 2012 2:23 PM Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity from [Tom W8JI]: The issue here is one of measurement distance and the assumed flat earth, and how much the ground wave contributes to low angle radiation. We obviously know radiation at zero degrees is not zero, as distant models show. broadcast consultant acquaintance of mine who has made helicopter measurements of the elevation patterns of MW monopoles.> My point is that does not tell us what happens at the ionosphere. If I just take a simple program like EZNEC, and use a small sense antenna out in the distance, the results follow the trend you posted from the helicopter. I certainly am not disputing that data, because it seems reasonable. AFAIK, we do not have measurements of arrival angles useful for long distances or how lower angles from verticals might apply to that. All we really know is using simple programs, low angle patterns are misleading. 73 Tom ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Just to point out that we don't have measurements of arrival angles at the ionosphere proving the fields shown in a NEC far-field analysis, either. Yet people seem to accept a NEC far-field pattern as gospel, even though it does not accurately show the radiation launched by a monopole at elevation angles below 10 degrees or so. We have a lot of things we claim as fact, even though we don't supporting data. Some border on magic. That's why I A-B test things for several months before deciding anything. :-) I installed a 300 foot tower because I remembered how well a dipole at 300 feet worked at a BC station. I was sure, based on the DX contacts, the dipole was a killer antenna for receiving and transmitting. Problem is when I finally installed that wonderful antenna after all that work, my vertical tied broadside to the dipole and badly beat the dipole off the dipole ends. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
"Tom W8JI" wrote: My point is that does not tell us what happens at the ionosphere. If I just take a simple program like EZNEC, and use a small sense antenna out in the distance, the results follow the trend you posted from the helicopter. ... AFAIK, we do not have measurements of arrival angles useful for long distances or how lower angles from verticals might apply to that. Just to point out that we don't have measurements of arrival angles at the ionosphere proving the fields shown in a NEC far-field analysis, either. Yet people seem to accept a NEC far-field pattern as gospel, even though it does not accurately show the radiation launched by a monopole at elevation angles below 10 degrees or so. R. Fry ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
- Original Message - From: "Richard Fry" To: Sent: Wednesday, October 24, 2012 2:23 PM Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity from [Tom W8JI]: The issue here is one of measurement distance and the assumed flat earth, and how much the ground wave contributes to low angle radiation. We obviously know radiation at zero degrees is not zero, as distant models show. My point is that does not tell us what happens at the ionosphere. If I just take a simple program like EZNEC, and use a small sense antenna out in the distance, the results follow the trend you posted from the helicopter. I certainly am not disputing that data, because it seems reasonable. AFAIK, we do not have measurements of arrival angles useful for long distances or how lower angles from verticals might apply to that. All we really know is using simple programs, low angle patterns are misleading. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
from [Tom W8JI]: The issue here is one of measurement distance and the assumed flat earth, and how much the ground wave contributes to low angle radiation. We obviously know radiation at zero degrees is not zero, as distant models show. As to measured data, below with his permission is a quote from a broadcast consultant acquaintance of mine who has made helicopter measurements of the elevation patterns of MW monopoles. These data below were taken using a helicopter at a horizontal distance of 2.8 km from the monopole, showing the fields existing at elevation angles of zero to about 3 degrees above the horizontal plane. This path length is short enough so that earth conductivity has little bearing on the measured fields, but not so short that the intrinsic, ~cosine-shaped elevation pattern of a 1/4-wave monopole will significantly affect the fields at those measured elevations. It will be seen from the data that no "notch" exists in the fields radiated by the monopole at elevation angles of 3 degrees and less, as expected by some when considering only the far-field patterns shown by MoM (NEC) software, and in antenna textbooks. That low-angle radiation is a space wave, not a ground wave, and given the right conditions it can reach the ionosphere to produce a sky wave. That sky wave can be very useful to hams using vertical monopoles, even though its existence may not be recognized. QUOTE Helicopter Vertical Calibration To check for variations in field intensity due to elevation above ground, we hovered over one location and rose from the ground at 50-foot intervals to 500 feet. Location #12 on the 230° radial was used (non-directional mode), and the data as presented below shows no significant effect. Measurements taken for this report were done at an average elevation of 500 feet and the calibration of the meter takes the vertical factor into account. Height above ground Field Intensity Variation from 0 feet 0 56 mV/m(Ref.) 50 56 +0.0 mV/m 100 56 +0.0 150 55-1.0 200 55-1.0 250 55-1.0 300 55-1.0 350 54-2.0 400 54-2.0 450 54-2.0 500 54-2.0 Averages: 54.91 mV/m -1.09 mV/m (-1.99%) END QUOTE ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
For DX we are interested in elevation angles from 3-15 degrees. How much error is there in a NEC model of a monopole at these elevations? Dave WX7G The issue here is one of measurement distance and the assumed flat earth, and how much the ground wave contributes to low angle radiation. We obviously know radiation at zero degrees is not zero, as distant models show. I'm not sure anyone has actually measured wave angle of typical signals, or actually measured how much very low angle fields contribute to the low angle radiation. Without measurements, we don't have solid theory. We have postulation, even if based on science. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
Dave WX7G wrote: For DX we are interested in elevation angles from 3-15 degrees. How much error is there in a NEC model of a monopole at these elevations? The link below shows the NEC4.2 fields for a seawater path on 1850 kHz. The calculated field at 1 km in the horizontal plane for 1 kW of applied power is 309 mV/m. The theoretical maximum field for that system at 1 km in the horizontal plane, over a perfect ground plane is 313 mV/m. The fields at low elevation angles above the horizontal plane are nearly the same. As NEC calculates the horizontal plane field accurately, the other fields shown there will be equally accurate. As shown in my earlier plot for seawater, 5 mS/m and 1 mS/m, the shapes of the elevation patterns close to a monopole are very similar to each other for those different conductivities. http://i62.photobucket.com/albums/h85/rfry-100/160m_Qtr_Wave_ElPat_at_1km.jpg R. Fry ___ Topband reflector - topband@contesting.com
Re: Topband: PreStew results
Hi, My only (50+ year old) top band transmitter quit (again) right at the beginning of the Stew. Before I repair it yet again I think I will just build something *new* in hopes of having it work for a while. 73, Bill KU8H On Sun, 2012-10-21 at 20:08 -0700, Tree wrote: > The results for the Stew Perry Warmup are now posted. > > Yes - the contest has only finished 12 hours ago - but we have received > almost 100 logs already. > > As more logs come in - they results will be updated. > > Go to http://www.kkn.net/stew and click on the link for the PreStew results. > > If you haven't sent in your log - please do so via e-mail to > t...@contesting.com. > > 73 Tree N6TR ___ Topband reflector - topband@contesting.com
Topband: Travails of The New "Topband" Season...
Good Day All, I am slowly unrolling all of the radial wires here for my seasonal three inverted "L" antennas---I say slowly because the arthritis in my knees has turned what USED to be a one day jaunt, into a protracted & laboured affair. Anyway, I have two "L's" completed, with one to go... But as if to add "insult" to "injury" here, I had the misfortune of unknowingly rolling about in a clump of poison ivy(!) last week, when I was readying the first "L"...! There are few things worse than having to contend with the after-effects of that nastiness. I only just hope that Topband conditions this year will MORE than make-up for all of my travails, and that the spotty effects of the past two years will quickly fade into distant memory...along with my poison ivy, that is...! ~73~ de Eddy VE3CUI - VE3XZ ___ Topband reflector - topband@contesting.com
