Re: Topband: Effect of trees- tree appreciation
Long delayed response to http://lists.contesting.com/pipermail/topband/2013-August/041954.html K2AV wrote: "By common expectation LPL and LR should have a propagation advantage over NY4A. LPL and LR both have excellent stacked 3 or 4 element 40m yagi's. But note how as the fourth mode is engaged, both LR and LPL fall off because they are not cleanly engaging the mode, most likely because the increasing elevation angle is starting into a notch in the yagi vertical pattern. Also note that NY4A carries the best signal for most of the 24 hours. This is an evaluation of the NY4A 40 EU quad vs. known excellent installations that is hard to argue with." From the ARRL results database, sorted by maximum 40m QSOs (after log-checking): http://bit.ly/19YAF1f don't worry Frank...it's OK :-) RankCall40m QSOs 1. K3LR2000 2. W3LPL 1911 3. WE3C1862 4. KM1W1818 5. NY4A1809 K3LR could be expected to have a higher total because of better prop to JA but the other 4 should have had similar propagation to EU, which would dominate their results. There's more to this story than RBN spots from a single location shows. 73, Bill W4ZV _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
It's very handy to have a close-by RBN node that can hear us on 160 in the daytime. This allows us to evaluate our signal independent of night-time variations in propagation. Note that the figure is signal to noise, not signal strength. So sometimes we will have a varying signal to noise report, even if the signal is steady, particularly at night, due to the varying level of noise. Once one gets used to the RBN concept, it's easy to pick out "quiet nights", and do other things to extract meaningful evaluation from RBN numbers. RBN will watch a signal over an entire contest, document the propagation modes changing and compare antennas from the same region, particularly on a quiet evening. To see one stellar example of this, go to http://www.reversebeacon.net/analysis/ Enter 02/19/2011 as the date. Click on the Europe bar. When the station selection expands, click on S50ARX. Enter NY4A, W3LPL, and K3LR under stations. Look at the 40 meter spots. On the right side of the graph for the zulu day, Saturday evening was for propagation one of those wide open very "smooth" propagation evenings analogous to reflections off a lake on a windless day. In particular, starting around 19Z or so, see how NY4A's strength goes through three jumps up to a plateau. You can see that LPL and LR climb them as well. These plateaus follow the propagation changing modes (numbers of hops and angle) as the band opens into the evening. Note that the NY4A 5 element long quad (at 84 feet center height, over 179 feet of catenary) engages all three modes cleanly and fully as they open, without any fading. If the path to EU from NY4A is cleanly open, the path must be open from LPL and LR distances. By common expectation LPL and LR should have a propagation advantage over NY4A. LPL and LR both have excellent stacked 3 or 4 element 40m yagi's. But note how as the fourth mode is engaged, both LR and LPL fall off because they are not cleanly engaging the mode, most likely because the increasing elevation angle is starting into a notch in the yagi vertical pattern. Also note that NY4A carries the best signal for most of the 24 hours. This is an evaluation of the NY4A 40 EU quad vs. known excellent installations that is hard to argue with. Can't be done like this without RBN. 73, Guy On Sat, Aug 10, 2013 at 10:14 PM, Bill Tippett wrote: > > " > > On Sat, Aug 10, 2013 at 7:47 PM, wrote: > > > > I haven’t used the RBN. Guess I need to figure out how so as to quantify > > the performance of what I have up. > > > > Is there a tutorial on the site? > > > I don't think so but go to "DX spots", then "spots analysis tool". > Then select a date (e.g. 02/16/2013 for the ARRL DX), a continent > (e.g. Europe) and a prolific RBN (e.g. DR1A) and add your call in the > box at the bottom. You can then add a competitor's call and see how > your signal strength compared over the 24 hours. You could also have > a buddy call CQ simultaneously on a different frequency and compare at > different RBN locations. > > If you want to check your own strength, Mike's advice will work. You > can also test different antennas yourself by calling CQ on even > minutes with one antenna and odd minutes with another. Then search > RBN for your call and note the signal strengths at even and odd minute > spots by RBNs. > > If you play around on the site you'll get the hang of it. > > 73, Bill W4ZV > _ > Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Mike, Thanks for the info on RBN. I am learning how to navigate thru RBN also. Very helpful. Bob K6UJ On Aug 10, 2013, at 5:11 PM, Mike Waters wrote: > I'm not sure if there's a tutorial, but let me see if we call help a > little. Since I probably have cookies saved from using them, you may > experience something a little different. > > Click http://www.reversebeacon.net/main.php. > > NO, better yet, try http://www.reversebeacon.net/dxsd1/ instead . You > should see some radio buttons and drop-down lists in two columns. > > 1. Leave the first column, "DX Station" alone. It should have the top radio > button checked and the drop-down list to its right should say "any". > > 2. Under the second column, "DE Station", click the last (4th) radio > button, and to its right, click the drop down list and chose "NA - North > America". > > 3. To the right of those under "Band", check the 160m checkbox. > > 4. Click the Proceed button on the left. (After I do that, the URL > http://www.reversebeacon.net/dxsd1/dxsd1.php?f=8014 appears. ) > > There are other options, such as the Ready Made Filters in the blue box > there to the right. I forget how those work, but try those too. > > You can zoom in on the map, choose grayline display, and other options. > > Try calling CQ on CW on a clear freq. and see how strong you are. :-) > > See if you can copy the stations there. > > 73, Mike > www.w0btu.com > > > > On Sat, Aug 10, 2013 at 6:47 PM, wrote: > >> I haven’t used the RBN. Guess I need to figure out how so as to quantify >> the performance of what I have up. >> >> Is there a tutorial on the site? >> > _ > Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
" On Sat, Aug 10, 2013 at 7:47 PM, wrote: > > I haven’t used the RBN. Guess I need to figure out how so as to quantify the > performance of what I have up. > > Is there a tutorial on the site? I don't think so but go to "DX spots", then "spots analysis tool". Then select a date (e.g. 02/16/2013 for the ARRL DX), a continent (e.g. Europe) and a prolific RBN (e.g. DR1A) and add your call in the box at the bottom. You can then add a competitor's call and see how your signal strength compared over the 24 hours. You could also have a buddy call CQ simultaneously on a different frequency and compare at different RBN locations. If you want to check your own strength, Mike's advice will work. You can also test different antennas yourself by calling CQ on even minutes with one antenna and odd minutes with another. Then search RBN for your call and note the signal strengths at even and odd minute spots by RBNs. If you play around on the site you'll get the hang of it. 73, Bill W4ZV _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
I'm not sure if there's a tutorial, but let me see if we call help a little. Since I probably have cookies saved from using them, you may experience something a little different. Click http://www.reversebeacon.net/main.php. NO, better yet, try http://www.reversebeacon.net/dxsd1/ instead . You should see some radio buttons and drop-down lists in two columns. 1. Leave the first column, "DX Station" alone. It should have the top radio button checked and the drop-down list to its right should say "any". 2. Under the second column, "DE Station", click the last (4th) radio button, and to its right, click the drop down list and chose "NA - North America". 3. To the right of those under "Band", check the 160m checkbox. 4. Click the Proceed button on the left. (After I do that, the URL http://www.reversebeacon.net/dxsd1/dxsd1.php?f=8014 appears. ) There are other options, such as the Ready Made Filters in the blue box there to the right. I forget how those work, but try those too. You can zoom in on the map, choose grayline display, and other options. Try calling CQ on CW on a clear freq. and see how strong you are. :-) See if you can copy the stations there. 73, Mike www.w0btu.com On Sat, Aug 10, 2013 at 6:47 PM, wrote: > I haven’t used the RBN. Guess I need to figure out how so as to quantify > the performance of what I have up. > > Is there a tutorial on the site? > _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
I haven’t used the RBN. Guess I need to figure out how so as to quantify the performance of what I have up. Is there a tutorial on the site? Cecil Acuff Gulfport MS K5DL From: Bill Tippett Sent: August 10, 2013 12:19 PM To: topband@contesting.com Subject: Re: Topband: Effect of trees- tree appreciation W8JI wrote: > My gut feeling is the one that looks the best and takes the most work will make you feel like you have the best signal you ever had, but no one else will notice the change except you unless you tell them about all the work or they "like" a particular antenna you are using. K2XT replied: > This is a a very significant statement when you think about it. Ask anyone you talk to on the air how he likes his antenna. Most will say they like it, it's doing great. Ask them how they know. If they understand your question you will get silence in response. Because almost no one KNOWS, or even knows how it compares to their previous antenna. But how they FEEL about it determines their satisfaction ! With the advent of ReverseBeacon.net, it's very easy to compare antennas with other stations. I've been doing this after each major contest and have learned other things such as QSB cycle depth and periodicity. I also test multiple antennas at home by time-stamping my transmissions and then reviewing the RBN data. This is so simple to do I don't know why anyone wouldn't use it to get comparative measurements. 73, Bill W4ZV _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Hi, Bill I've met you in the past - I believe at some of the "Swan" meetings with K4CIA and others here in Raleigh. I was first Licensed as KN4OTV in 1957, when I had just turned 13. I saw your post today on the topband reflector and I looked you up on QRZ.com. I remember when KN4RID made DXCC in 1958, but I didn't realize until today that KN4RID was you!! Small world, I guess!! I remember how impressed I was because back then, the Novice license was issued for 1 year, so a person would really have had to scramble to get 100 worked and confirmed in a year!! FB!! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill Tippett Sent: Saturday, August 10, 2013 1:20 PM To: topband@contesting.com Subject: Re: Topband: Effect of trees- tree appreciation W8JI wrote: > My gut feeling is the one that looks the best and takes the most work will make you feel like you have the best signal you ever had, but no one else will notice the change except you unless you tell them about all the work or they "like" a particular antenna you are using. K2XT replied: > This is a a very significant statement when you think about it. Ask anyone you talk to on the air how he likes his antenna. Most will say they like it, it's doing great. Ask them how they know. If they understand your question you will get silence in response. Because almost no one KNOWS, or even knows how it compares to their previous antenna. But how they FEEL about it determines their satisfaction ! With the advent of ReverseBeacon.net, it's very easy to compare antennas with other stations. I've been doing this after each major contest and have learned other things such as QSB cycle depth and periodicity. I also test multiple antennas at home by time-stamping my transmissions and then reviewing the RBN data. This is so simple to do I don't know why anyone wouldn't use it to get comparative measurements. 73, Bill W4ZV _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
This is a VERY profound piece of advice! The RBN showed me that something was definitely wrong with my TX signal level this summer. It was considerably down from several other stations not that far away, even with 1500 watts. And it wasn't like that at all at first; before the foliage started growing, my signal levels on the RBN was much better. I can't prove that it's the weeds or leaves near my antenna, (and don't have the time to now), but without the RBN, I may have never suspected anything was wrong. http://www.reversebeacon.net/dxsd1/dxsd1.php?f=797 73, Mike www.w0btu.com On Sat, Aug 10, 2013 at 12:19 PM, Bill Tippett wrote: > With the advent of ReverseBeacon.net, it's very easy to compare antennas > with other stations. I've been doing this after each major contest and > have learned other things such as QSB cycle depth and periodicity. > > I also test multiple antennas at home by time-stamping my transmissions > and then reviewing the RBN data. This is so simple to do I don't know why > anyone wouldn't use it to get comparative measurements. > _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
W8JI wrote: > My gut feeling is the one that looks the best and takes the most work will make you feel like you have the best signal you ever had, but no one else will notice the change except you unless you tell them about all the work or they "like" a particular antenna you are using. K2XT replied: > This is a a very significant statement when you think about it. Ask anyone you talk to on the air how he likes his antenna. Most will say they like it, it's doing great. Ask them how they know. If they understand your question you will get silence in response. Because almost no one KNOWS, or even knows how it compares to their previous antenna. But how they FEEL about it determines their satisfaction ! With the advent of ReverseBeacon.net, it's very easy to compare antennas with other stations. I've been doing this after each major contest and have learned other things such as QSB cycle depth and periodicity. I also test multiple antennas at home by time-stamping my transmissions and then reviewing the RBN data. This is so simple to do I don't know why anyone wouldn't use it to get comparative measurements. 73, Bill W4ZV _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Thank you all for the replies regarding the "T" versus "L" rebuild for my 160 antenna. I'm on a 120x120' city lot in Fairbanks. For fun look me up in QRZ, under 'Detail' zoom in for a satellite view via Google, then switch to a street view to see the trees. The motorhome is gone, the motorcycle is replaced with another, and the tower and trees still stand. The T would be strung between two spruce trees to the W of the home. Not the best scenario as the available tree spacing is a close ~75', the T wires would be touching the top of each tree trunk, and any excess for trim would drop down next to each trunk as well. A breeze would flex the trees and cause the vertical portion to rise and fall possibly affecting tuning. The L (mimicking my former 160 antenna that came down with a blown tree) would climb a 75-80' tree adjacent to the SW corner of the home, be held away 5-7' from the trunk via branches except for the very top, and the remaining ~55' horizontal portion would head towards the street to the south but not reach the support, again at 75-80'. Eight tuned radials at ~15' are strewn where possible around the property. After some thought and your discussion, I think I'll repeat the L as it's easy to shoot the support ropes from the house roof. The T would be harder, and one end would be close to the power line that adjoins the north edge of the property. Adjusting resonance for the T would require lowering the whole deal a few times from both supports. Adjusting the L is simpler and only requires loosening the horizontal leg and shortening or lengthening the base of the vertical part. Plus I already have a big feed line choke and 3:1 matching unit built from the previous setup. We'll see what happens, 73, Gary NL7Y _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Here is a little data in a sea of complexity: My 160m T is 10' up at the base with 6 x 125' radials elevated ten feet (4 more planned), in a mixed hemlock/red cedar/alder forest/clear area. The top is at 87' and the T arms are 42' each side at the same height. The vertical wire (13ga insulated CCS) is about 18" from the trunk. When I put it up, one T arm snagged on branch stubs on the supporting healthy hemlock and only extended out about 17'. The other 25' was tight (3-4") to the trunk. Fed thru a 50::25 ohm balun and 4000k ohm choke the resonance was 1835KHz and swr 1.1:1 - victory! Then I had a tree climber remove the branch stubs, and clear a few interfering branches at 90'. The problem arm was extended to its full length. Now both arms are 42' each side pretty much in the clear. Resonance dropped to 1785KHz. So, now I need to lower everything and cut off some wire. All the original dimensions were chosen by EZNEC for 1835, so the tree loading had/has a significant effect, as luck would have it, to right on the design numbers with the snagged arm. This thread has been helpful and now my plan is to have the high voltage parts of an antenna away from living wood. If I ever redo the installation, I would also opt to move the top of the vertical section as far as mechanically feasible from the tree, probably 3 or 4'. An even better solution would be to support the whole T between two trees, but that won't work for my radial field. Keeping T arms away from wood by 5 to 10' seems like a good idea IMO. As far as performance, I have no way to verify it. This is my first "serious" 160m antenna and I felt in last winters SSB contest (my first 160 contest also) it wasn't a great performer. But from 48N (Redmond, WA) we "suffering sevens" are frequently wondering who the folks in 1,2,3,4, and 5 land are talking to. 64N sounds like a heck of a challenge! However, it "looks good" so should "work well," particularly since it will be "improved" for the next contest. Grant KZ1W On 8/9/2013 9:31 PM, Gary and Kathleen Pearse wrote: Where are the high voltage points in a "T" antenna? I have the choice of putting up either a new T between two trees, or an L again on 160M. The ends of the T would by necessity be strung over and go down 20-30' alongside the two supporting trees. The L would parallel a tree and bend over at around 75-80'. The horizontal end of the L would end up 20-30' from its tree support. I'd reuse my 8 tuned elevated radials, plus maybe a couple more. Suggestions? Sometimes high angle works better in our tilted ionosphere at 64N. 73, Gary NL7Y _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
W8JI says: >My gut feeling is > the one that looks the best and takes the most work will make you feel like > you have the best signal you ever had, but no one else will notice the > change except you This is a a very significant statement when you think about it. Ask anyone you talk to on the air how he likes his antenna. Most will say they like it, it's doing great. Ask them how they know. If they understand your question you will get silence in response. Because almost no one KNOWS, or even knows how it compares to their previous antenna. But how they FEEL about it determines their satisfaction ! Tom, it seems like your lifetime goal is to dispel myths and wives tails, and bring logical reasoning to ham radio. I hope you are succeeding at it. At least I hope you don't ever give up. Rick K2XT _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
On 8/10/2013 6:28 AM, Tom W8JI wrote: This is a good example where the problem of not quantifying things comes in. No one here knows what the typical loss or interation is, and it is probably impossible to know what the extact interation is in every situation. Yes, and that's exactly why those who ask these questions are asking them. I don't think anyone can answer any questions about this with more than a guess. Yep. My suggestions were a "somewhat educated guess." :) 73, Jim K9YC _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Where are the high voltage points in a "T" antenna? The highest voltage is generally at the open end, but how high that voltage is depends on the boundary area between the antenna and whatever is around the antenna. The slippery slope here is that people might think only the very ends have high potential or might add significant loss, and that distance is the only factor. Loss is a complex issue. Just as current density and resistivity in a given volume are determining losses, so is the area and media the field is distributed over. The point is, moving an end away at the expense of an overall increase in area exposed to a lesser "voltage" might not be a good solution. I have the choice of putting up either a new T between two trees, or an L again on 160M. The ends of the T would by necessity be strung over and go down 20-30' alongside the two supporting trees. The L would parallel a tree and bend over at around 75-80'. The horizontal end of the L would end up 20-30' from its tree support. I'd reuse my 8 tuned elevated radials, plus maybe a couple more. This is a good example where the problem of not quantifying things comes in. No one here knows what the typical loss or interation is, and it is probably impossible to know what the extact interation is in every situation. I think interaction is modest unless the conductor is right in the foliage. Based on one element I had with one large pecan tree, it was a 130 ft element probably 40-60 feet from the trunk, I saw maybe ten percent increase in base resistance. That tree was probably 60-80 feet tall, so it was nowhere near the open end. The branch tips from that tree were within 10-15 feet of areas of that antenna. I don't think anyone can answer any questions about this with more than a guess. The T might might be better, worse, or the same. My gut feeling is the one that looks the best and takes the most work will make you feel like you have the best signal you ever had, but no one else will notice the change except you unless you tell them about all the work or they "like" a particular antenna you are using. 73 Tom _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
On 8/9/2013 9:31 PM, Gary and Kathleen Pearse wrote: Where are the high voltage points in a "T" antenna? The end of an antenna (for example, at the end insulator of a wire antenna) MUST be a current minimum (near zero) because there is no place for it to go except by capacitance to space or surrounding objects. A mathematician or engineer would call this a "boundary condition." Where there is a current minimum, there is a voltage maximum, and because impedance is the ratio of voltage to current, it is a high impedance point. If the antenna is a half wave or longer, there will usually be another high impedance (high voltage) point one half wave from the end. The Tee would seems the better solution, because it puts the high current parts of the antenna farther from the tree, but I would try to avoid having the ends in close contact with the tree(s). There are several ways this might be avoided. 1) Because the horizontal wire(s) that form the top of the tee are, in essence, providing capacitance to lengthen the antenna. The top wires can be shorter, yet be equally effective, if there are more of them. So if your real estate, or your trees allow that, it's a very good solution. 2) The primary function of the horizontal wires (top loading) is to make the antenna resonant, so that it loads more easily. But there's nothing wrong with letting it be a bit short -- that's why there are antenna tuners, and all sorts of possible matching networks. Another important point associated with #2 is that the loss in coax is quite low on 160M, even with a fairly high VSWR. Loss will be a lot lower with bigger coax (like RG8). 3) The third option is a loading coil at the base. 73, Jim K9YC _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Where are the high voltage points in a "T" antenna? I have the choice of putting up either a new T between two trees, or an L again on 160M. The ends of the T would by necessity be strung over and go down 20-30' alongside the two supporting trees. The L would parallel a tree and bend over at around 75-80'. The horizontal end of the L would end up 20-30' from its tree support. I'd reuse my 8 tuned elevated radials, plus maybe a couple more. Suggestions? Sometimes high angle works better in our tilted ionosphere at 64N. 73, Gary NL7Y _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
I expect the losses are related to current not voltage. The current of my antenna is in the vertical section for the most part and loss would would have to happen there as coupled to the nearest tree. The current would have to flow to ground so I seriously doubt if the resistance of the trunk is low enough to conduct any significant current to ground. Any loss in the top hat where the voltage is probably would amount to much power; the current has already flowed in the vertical section where I want it to. While I'm sure you are right about losses, and the losses are probably somewhat small, it isn't for the reason above. The real reason is a tree has such high resistance it can't sap (pardon) most of your TX power. The same things that make a tree a terrible (or virtually nonexistent) antenna also cause it to not have significant effect unless the electric field is right into the tree, or it is a pretty thick woods. The problem is no one really know how much loss there really is. But the antenna is a closed system. A high resistance to ground at the high voltage end of things can cause just as much loss as a low series resistance at the current end of things. It **isn't ** that current has already flowed past where you wanted it. It isn't that because it flowed, losses at the top do not matter. Losses at the voltage point certainly do matter. You can create a pretty poor antenna if you terminate the open end of a short antenna in a resistance. The real reason antennas in trees make people happy is the loss in the system making them happy is not really noticeable to them. I can't notice 6 dB loss at times, unless with an A-B test or by measuring things. 73 Tom _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
On 08/09/2013 04:51 PM, Charlie Cunningham wrote: As a DXer, I generally listened a lot, and I found that on 160, if I could hear them - more often than not, I could work 'em - wherever in the world they might be. No receive antennas? With 1500 watts into a 100 foot vertical (tower with 7 element 6 meter beam for top loading and nearly 10K feet of wire in radials), and a collection of at best mediocre reversible Beverages, there is a lot I can hear but not work. 73, Paul N1BUG _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
You're a man after my own heart, Greg! I never worried so much about the "Dbs". As a DXer, I generally listened a lot, and I found that on 160, if I could hear them - more often than not, I could work 'em - wherever in the world they might be. Aside from 160, I have also built fearsome 3-el 40m vertical yagis for special paths, like Bouvet and Peter 1, that enabled me to work them on first call in huge east coast pileups! So, I figure if I'm working what what I can hear, and break through monster pileups for the tough ones, then I probably don't need to sweat or "nit-pick" the real or imagined tree losses! I also built a big 5-element 80m steerable vertical array (supported by trees) that was a fearsome "world-beater". Trees have been very good to me! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Greg Chartrand Sent: Friday, August 09, 2013 4:21 PM To: topband@contesting.com Subject: Re: Topband: Effect of trees- tree appreciation I expect the losses are related to current not voltage. The current of my antenna is in the vertical section for the most part and loss would would have to happen there as coupled to the nearest tree. The current would have to flow to ground so I seriously doubt if the resistance of the trunk is low enough to conduct any significant current to ground. Any loss in the top hat where the voltage is probably would amount to much power; the current has already flowed in the vertical section where I want it to. I had one of the top hat wires break once due to an apparent arc to a tree limb. My solution was wire with better insulation, so far so good. I couldn't care less about any speculated loss due to my trees. Without them I would not have an antenna on 160 so I figure I'm probably at least +50 db compared to my dummy load and many db better that a makeshift antenna away from the trees. I'd encourage anyone considering 160 to use trees to suspend an antenna if they are available. If I had a nice 100' tree in my backyard I guarantee you I'd use it. I also guarantee that I'd spend a hell of a lot of money putting up an equivalent tower in the open and the DB difference would not be worth the effort and cost for me. Again, thank you trees. - Greg Chartrand - W7MY Richland, WA. W7MY Home Page: http://webpages.charter.net/w7my/ > _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
I expect the losses are related to current not voltage. The current of my antenna is in the vertical section for the most part and loss would would have to happen there as coupled to the nearest tree. The current would have to flow to ground so I seriously doubt if the resistance of the trunk is low enough to conduct any significant current to ground. Any loss in the top hat where the voltage is probably would amount to much power; the current has already flowed in the vertical section where I want it to. I had one of the top hat wires break once due to an apparent arc to a tree limb. My solution was wire with better insulation, so far so good. I couldn't care less about any speculated loss due to my trees. Without them I would not have an antenna on 160 so I figure I'm probably at least +50 db compared to my dummy load and many db better that a makeshift antenna away from the trees. I'd encourage anyone considering 160 to use trees to suspend an antenna if they are available. If I had a nice 100' tree in my backyard I guarantee you I'd use it. I also guarantee that I'd spend a hell of a lot of money putting up an equivalent tower in the open and the DB difference would not be worth the effort and cost for me. Again, thank you trees. - Greg Chartrand - W7MY Richland, WA. W7MY Home Page: http://webpages.charter.net/w7my/ > _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
On 8/8/2013 10:09 AM, donov...@starpower.net wrote: I caught a tree on fire at night because the end of my dipole was in some dead tree branches! One of the first antennas I hung when I moved here was a horizontal dipole for 80 with loading coils for 160M, built with THHN. One end was touching a branch. When I took it down to re-rig it, I discovered that the white insulation was rather scorched, clearly indicating some arcing to the branch. Another thing I tried was loading a 160M wire vertical on 80M, using a big tapped inductor as a transformer, with a piece of open coax to resonate it. The coax laid on the ground, which was covered with dry grass (this was early fall, when we hadn't had rain since April, very common here). I had only transmitted for a few minutes, and came outside to see that the open end of the coax, which I had left open because I was still tuning it's length, had nearly started that grass on fire. The reason for both of these events is simple -- the points in contact with vegetation were very high voltage points. 73, Jim K9YC _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
When I was a teenager chasing Gus Browning on 40 meters I caught a tree on fire at night because the end of my dipole was in some dead tree branches! My parents were not happy... 73 Frank W3LPL - Original Message - From: "Tim Shoppa" To: "Tom W8JI" , "Rick Stealey" , topband@contesting.com Sent: Thursday, August 8, 2013 6:04:24 PM Subject: Re: Topband: Effect of trees- tree appreciation Different folks here have promulgated a "high voltage point loss" model for antennas in trees. I think this could be a valid model for a doublet hung with wires directly touching wet tree branches, I'm sure at high enough power level this could burn away some of the tree probably at a high voltage point on the wire. But my feeling (having done some VHF/UHF foliage loss modeling in my day job) is that the "heat distributed over several thousand feet of tree trunk" or "heat distributed over several million leaves" is the correct model if the wire isn't actually brushing against a tree. Interestingly enough one of my favorite VHF/UHF foliage loss models notes that vertical polarization losses at VHF are higher than horizontal polarization, and they say this is due to "tree morphology" i.e. the tree is taller than it is wide :-). They also note that most of the models that work best at VHF/UHF, do underestimate loss at HF, so maybe there is no good verified and published model for HF loss much less MF loss in trees. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Thursday, August 08, 2013 12:40 PM To: Rick Stealey; topband@contesting.com Subject: Re: Topband: Effect of trees- tree appreciation > > Just thinking here - I can hold my hand on a 75 watt lightbulb for a > few seconds. 10 of those lightbulbs-worth of heat isn't very much > heat, dissipated over the surface area of the bark of a tree, 60 feet > tall, in winter, with low temps, and maybe even some wind can't really > have much in the way of visible impact, could it? Gone up in flaming glory? > Good logical thinking. It's difficult to know a 6 dB change without measurement, let alone three dB. Take a tank coil as an example. Even 50 watts of loss could make it smoke or melt if the loss is concentrated in one small area, say just a few turns. If loss is spread over enough area, even 1000 watts power loss might not be noticeable. This not only applies to trees, it applies to everything from ferrite cores to transmission lines. 0.1 dB loss in a coax connector can melt it down at amateur power levels, 10 dB loss in a 100-foot cable might be unnoticeable. 73 Tom _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Different folks here have promulgated a "high voltage point loss" model for antennas in trees. I think this could be a valid model for a doublet hung with wires directly touching wet tree branches, I'm sure at high enough power level this could burn away some of the tree probably at a high voltage point on the wire. But my feeling (having done some VHF/UHF foliage loss modeling in my day job) is that the "heat distributed over several thousand feet of tree trunk" or "heat distributed over several million leaves" is the correct model if the wire isn't actually brushing against a tree. Interestingly enough one of my favorite VHF/UHF foliage loss models notes that vertical polarization losses at VHF are higher than horizontal polarization, and they say this is due to "tree morphology" i.e. the tree is taller than it is wide :-). They also note that most of the models that work best at VHF/UHF, do underestimate loss at HF, so maybe there is no good verified and published model for HF loss much less MF loss in trees. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Thursday, August 08, 2013 12:40 PM To: Rick Stealey; topband@contesting.com Subject: Re: Topband: Effect of trees- tree appreciation > > Just thinking here - I can hold my hand on a 75 watt lightbulb for a > few seconds. 10 of those lightbulbs-worth of heat isn't very much > heat, dissipated over the surface area of the bark of a tree, 60 feet > tall, in winter, with low temps, and maybe even some wind can't really > have much in the way of visible impact, could it? Gone up in flaming glory? > Good logical thinking. It's difficult to know a 6 dB change without measurement, let alone three dB. Take a tank coil as an example. Even 50 watts of loss could make it smoke or melt if the loss is concentrated in one small area, say just a few turns. If loss is spread over enough area, even 1000 watts power loss might not be noticeable. This not only applies to trees, it applies to everything from ferrite cores to transmission lines. 0.1 dB loss in a coax connector can melt it down at amateur power levels, 10 dB loss in a 100-foot cable might be unnoticeable. 73 Tom _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
Just thinking here - I can hold my hand on a 75 watt lightbulb for a few seconds. 10 of those lightbulbs-worth of heat isn't very much heat, dissipated over the surface area of the bark of a tree, 60 feet tall, in winter, with low temps, and maybe even some wind can't really have much in the way of visible impact, could it? Gone up in flaming glory? Good logical thinking. It's difficult to know a 6 dB change without measurement, let alone three dB. Take a tank coil as an example. Even 50 watts of loss could make it smoke or melt if the loss is concentrated in one small area, say just a few turns. If loss is spread over enough area, even 1000 watts power loss might not be noticeable. This not only applies to trees, it applies to everything from ferrite cores to transmission lines. 0.1 dB loss in a coax connector can melt it down at amateur power levels, 10 dB loss in a 100-foot cable might be unnoticeable. 73 Tom _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
> For them to make a significant impact on my ability to transmit, they would > have to absorb at least 3db (750 watts). So your loss is less than 3 db, and so it's of no concern to you? I know 160 meter ops who would, and do, pay lots of money for an extra 3 db. Say your tree loss was really 5 db (or even 10) you would know, based on what? The amount of DX worked last winter? >I suspect they would have gone up in flaming glory Just thinking here - I can hold my hand on a 75 watt lightbulb for a few seconds. 10 of those lightbulbs-worth of heat isn't very much heat, dissipated over the surface area of the bark of a tree, 60 feet tall, in winter, with low temps, and maybe even some wind can't really have much in the way of visible impact, could it? Gone up in flaming glory? Rick K2XT _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
I share your opinions and sentiments, Greg! Over the years I've worked some pretty good stuff around the world on 160 with inverted- Ls held up by trees, running a bit less power than you - abt 500-600W out from a home-brew 3-500Z. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Greg Chartrand Sent: Wednesday, August 07, 2013 5:51 PM To: topband@contesting.com Subject: Re: Topband: Effect of trees- tree appreciation I love my trees. They have held up my 160 antennas at my QTH for the last 18 years. For them to make a significant impact on my ability to transmit, they would have to absorb at least 3db (750 watts). If any of them have absorbed that amount of power, I suspect they would have gone up in flaming glory long ago. Obviously its less than 3 db and probably less than 1 db. I suspect I loose far more DB's in my Teflon like volcanic soil that the trees will ever contribute. In any case, THANK YOU TREES for being there for me! Greg - Greg Chartrand - W7MY Richland, WA. W7MY Home Page: http://webpages.charter.net/w7my/ > _ Topband Reflector _ Topband Reflector
Re: Topband: Effect of trees- tree appreciation
I love my trees. They have held up my 160 antennas at my QTH for the last 18 years. For them to make a significant impact on my ability to transmit, they would have to absorb at least 3db (750 watts). If any of them have absorbed that amount of power, I suspect they would have gone up in flaming glory long ago. Obviously its less than 3 db and probably less than 1 db. I suspect I loose far more DB's in my Teflon like volcanic soil that the trees will ever contribute. In any case, THANK YOU TREES for being there for me! Greg - Greg Chartrand - W7MY Richland, WA. W7MY Home Page: http://webpages.charter.net/w7my/ > _ Topband Reflector
