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Oddity of ground mounted antenna's.
Hi Gang
I recently moved from a fairly flat state to one that is mountainous. In getting to know the local area hams I have visited quite a few this past year. Several of them have their ground mounted HF antenna's perpendicular to the grade of the land rather than vertical. In other words, the top of the antenna is roughly 90 inches off center toward the downhill side. The only reasoning I have received thus far is it works better that way here. But not everyone adheres to doing it that way, all commercial antenna's are vertical. What Gives? TTUL Gary |
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Hello Gary,
Don't know from personal experience, but Les Moxon, author of HF Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. Good luck. Chuck |
There's a breed of Algerian goats with legs on one side longer than the
other. They live on the sides of steep mountains. |
Since NEC cannot model a sloping ground, just try modeling a leaning
vertical, and see how it effects the pattern. I seriously doubt there would be much difference. Certainly nothing you would notice. Frank "Richard Clark" wrote in message ... On 02 Dec 2004 11:51:12 EST, am (Gary V. Deutschmann, Sr.) wrote: What Gives? Hi Gary, Do they have the faith to build their walls that way too? Look at the horizontals. Do they ridge run, or do they follow the down hill slope too? The better question is: How much better is theirs than their neighbor's vertical (as opposed to their perpendicular)? The best question is: How do they know? Kinda reminds me of the Katherine Hepburn movie "Bringing Up Baby" where she breaks one heel of her high heels and starts loping along: "I feel like I was born on the side of a hill." 73's Richard Clark, KB7QHC |
Reg Edwards wrote:
There's a breed of Algerian goats with legs on one side longer than the other. ....and to go back the way they came, they must walk backwards? They live on the sides of steep mountains. Cheers - LH |
Reg Edwards wrote:
There's a breed of Algerian goats with legs on one side longer than the other. ....and to go back the way they came, they must walk backwards? They live on the sides of steep mountains. Cheers - LH |
This can easily be done with the free EZNEC demo program available from
http://eznec.com. Here's a step-by-step for the demo or any other EZNEC v. 4.0 program: 1. Open example file Vert1.EZ. (Click the Open button, enter Vert1, then click Open in the file selection window.) 2. Click FF Plot to generate a 2D elevation plot of the vertical antenna. 3. In the 2D Plot Window, open the File menu, select Save Trace As, enter a name in the blank box, and click Save. You can close the 2D Plot Window to get it out of the way. 4. Click the View Ant button so you can see what you're doing. 5. Click on the Wires line in the large white window to open the Wires Window. 6. In the Wires Window, open the Wires menu and select Rotate Wires. (This feature isn't available in EZNEC v. 3.0 or earlier versions.) 7. In the Rotate Wires dialog box, make the following changes: Rotation Amount: Enter the angle of the ground slope, and change the direction to CW (to simulate ground sloping down to the right) Rotation Axis: Y Then click Ok. You'll now see the tilted antenna. (The rotation will seem to be CCW, but that's because we're looking at the Y axis in the minus direction.) 8. Click FF Plot to generate a 2D plot. 9. In the 2D Plot window, open the File menu and select Add Trace. Enter the name of the plot of the vertical you saved earlier and click Open. You'll now see the plots of the vertical and tilted antenna superimposed. 10. If you'd like to see the dB difference between plots at any elevation angle, click the name of the recalled trace near the upper left corner of the plot window. The cursor will jump to the recalled trace, and the difference in dB appears as the bottom line of the right column in the data window below the plot. (This feature isn't available in EZNEC v. 3.0 or earlier versions.) If you don't see the data window, open the View menu and click Show Data. You can move the cursor by dragging it with the mouse, or with the arrow keys. 11. To see what the patterns would look like when the ground is tilted, print the plot (File/Print Plot), then rotate it clockwise by the angle of the ground tilt. Note that this assumes that the ground is flat and continues forever at the tilt angle, which of course can't be true. But it'll give you a good general idea of the effect of tilting the antenna. If you get confused about how the plot is oriented relative to the antenna, go to the View Antenna display. Open the View menu, select Objects, then check the 2D Pattern box. This will superimpose a correctly oriented 2D pattern on the drawing of the antenna. I did the experiment using a 30 degree tilt, and found a difference of 1.31 dB at an indicated elevation angle of 30 degrees. That would be at the horizon, taking into account the ground tilt. At an indicated elevation angle of 40 degrees (10 degrees above the horizon when ground tilt is considered), the difference is 1.77 dB. You can modify the ground conductivity and permittivity and repeat the experiment to see how this changes with different ground types. Roy Lewallen, W7EL Frank wrote: Since NEC cannot model a sloping ground, just try modeling a leaning vertical, and see how it effects the pattern. I seriously doubt there would be much difference. Certainly nothing you would notice. Frank |
On Thu, 02 Dec 2004 13:45:35 -0800, Roy Lewallen
wrote: I did the experiment using a 30 degree tilt, and found a difference of 1.31 dB at an indicated elevation angle of 30 degrees. That would be at the horizon, taking into account the ground tilt. Hi All, This is a pretty radical slope. The one I lived on was closer to 20-25 degrees and it was (with low brush) a bear to climb (and to fall without holding a rope for balance). When I do the trig for 30 degrees and stand with my feet one foot apart, shoulders and hips aligned with the slope, that leaves one foot 7 inches higher than the other. That's gonna take some stilleto heels. ;-) That aside for the heartier cragsmen, this also presumes (from EZNEC's propensity for a flat earth far field model) that the slope is infinte (or a pretty tall hill indeed). Gee, on that hill everything must be line of sight anyway! Who needs skip? But then, no one lives in the valley. :-( 73's Richard Clark, KB7QHC |
Reg Edwards wrote: There's a breed of Algerian goats with legs on one side longer than the other. ...and to go back the way they came, they must walk backwards? Cheers - LH ======================================== No! They just keep walking in the same direction. They have inherited a gene for sensing contour lines, never failing to get to where they want to be. Hannibal, around 219BC, being unaware of genes in those ancient days, considered mountain goats could be useful on the famous crossing of the Swiss Alps on his way to Rome. But on second thoughts he decided to use elephants who, as you know, walk trunk-to-tail. Neither he nor the elephants quite made it to Rome. --- Reg |
chuck wrote:
Don't know from personal experience, but Les Moxon, author of HF Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. The advantages of which Moxon wrote are for *horizontal* polarization only. If the antenna height above ground is correct, the ground reflection can reinforce low-angle radiation in the downslope direction. But Moxon also shows specifically that there are *no* such advantages for vertical polarization. The ground-reflected ray is lost at a high angle. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
"Roy Lewallen" wrote in message ... This can easily be done with the free EZNEC demo program available from http://eznec.com. Here's a step-by-step for the demo or any other EZNEC v. 4.0 program: 1. Open example file Vert1.EZ. (Click the Open button, enter Vert1, then ......... .........Objects, then check the 2D Pattern box. This will superimpose a correctly oriented 2D pattern on the drawing of the antenna. I did the experiment using a 30 degree tilt, and found a difference of 1.31 dB at an indicated elevation angle of 30 degrees. That would be at the horizon, taking into account the ground tilt. At an indicated elevation angle of 40 degrees (10 degrees above the horizon when ground tilt is considered), the difference is 1.77 dB. You can modify the ground conductivity and permittivity and repeat the experiment to see how this changes with different ground types. Roy Lewallen, W7EL Frank wrote: Since NEC cannot model a sloping ground, just try modeling a leaning vertical, and see how it effects the pattern. I seriously doubt there would be much difference. Certainly nothing you would notice. Frank Thanks for the info, but I already have the EZNEC demo. It does seem to be an excellent program, providing a low cost antenna modeling tool. I have been using another version of NEC for quite a few years and, to be honest, I prefer to work directly with the NEC cards. I feel lost if I cannot get in and edit the lines of code. I must admit I often use some of the additional program features to check if I have the correct card sequence, and also for tag rotation. I can also use any card listed in the NEC User's Guide. Fact is I was not that interested in actually modeling a leaning vertical, although the problem is trivial. Now that you have done it, I may give it a try to see if I get the same results. Assume you used a slightly elevated radial ground plane with the S/N ground model applied. Regards, Frank |
Hi Chuck
At least we have one sane person in the group eh! I moved from St. Louis to Knoxville last year, as of yet I have not installed my HF9V here, in St. Louis it was mounted vertical on flat ground with about 3,500 feet of radials. The only logical place for me to install my antenna is some 100 feet below the top of our hill, because of the radial bed. The grade of the hill is roughly a 30 inch average drop every 10 feet at the top of the hill. Unless I build an elevated counterpoise that would have one side of it about 20 feet in the air, how would the underground radials affect the operation of the antenna if it is vertical? Of the hams I have spoken with, those that have theirs vertical say there is no difference whether the antenna is vertical or not, and they should be mounted vertically. Of those that have theirs leaning perpendicular to the grade line, they claim they could not communicate with certain stations when their antenna was vertical, but can with it perpendicular. Although Knoxville is considered to be in a Valley, my home is situated on the north slope near the top of one of the foothills, but my property does go to the top, unfortunately, a little too far away from the house for the VHF/UHF, but it is roughly 30 feet above the crest of the hill, 60 feet above ground level at the shack. I guess I could install two separate mounts, one vertical and one perpendicular and try both ways, but retuning those HF9V's especially when you have the 160 coil is a real nightmare. FWIW: I cleared a line through the woods to run some dipoles. My first installation I mounted the dipoles horizontal with the grade line. But after putting up the VHF/UHF tower I moved many of the dipoles upward so they are closer to level. On the higher bands I did notice some difference, but on the lower bands they seemed to work about equally as well. It seems all the 10 meter paper chasers have their ground mounted antennas perpendicular to the ground, while serious hams have theirs all mounted vertically. Even those hams who live in the bottom of the valley have no trouble with HF communications, but those on top of hills often use large beams and yagi's to take advantage of their prime location. I have no antenna restrictions at my new home here, Yeah, other than what the FAA dictates regarding lighting if they are over a certain height. TTUL Gary chuck verbositized: Hello Gary, Don't know from personal experience, but Les Moxon, author of HF Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. Good luck. Chuck |
And only walk in one direction?
"Reg Edwards" wrote in message ... There's a breed of Algerian goats with legs on one side longer than the other. They live on the sides of steep mountains. |
In message , Richard Clark
writes On 02 Dec 2004 11:51:12 EST, am (Gary V. Deutschmann, Sr.) wrote: What Gives? Hi Gary, Do they have the faith to build their walls that way too? Look at the horizontals. Do they ridge run, or do they follow the down hill slope too? The better question is: How much better is theirs than their neighbor's vertical (as opposed to their perpendicular)? The best question is: How do they know? Kinda reminds me of the Katherine Hepburn movie "Bringing Up Baby" where she breaks one heel of her high heels and starts loping along: "I feel like I was born on the side of a hill." Did you know that the sheep in Wales have shorter legs on one side than the other? To allow them to graze more easily on the hillsides. Mike |
"Gary V. Deutschmann, Sr." wrote in message Several of them have their ground mounted HF antenna's perpendicular to the grade of the land rather than vertical. In other words, the top of the antenna is roughly 90 inches off center toward the downhill side. That vertical must be *downhill* from the house - else loss of sleep will occur. And wouldn't the uphill guy wires need to be doubled up ? --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.799 / Virus Database: 543 - Release Date: 11/20/2004 |
Hello, Ian.
Yes, I was a bit hasty in citing Moxon. But thinking a little more about this I wonder. Intuitively, and looking at Moxon's sketch, it would seem that the effect would be simply to rotate the vertical pattern by the amount of the slope. Aiming the pattern "down the slope" rather than "toward the horizon" does not seem to be a necessarily worse situation as Moxon suggests. Wouldn't that actually put more energy out toward the horizon? Tilting a VHF ground plane antenna toward the horizon would be different because the vertical pattern at zero degrees is not attenuated by ground losses. Chuck Ian White, G3SEK wrote: chuck wrote: Don't know from personal experience, but Les Moxon, author of HF Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. The advantages of which Moxon wrote are for *horizontal* polarization only. If the antenna height above ground is correct, the ground reflection can reinforce low-angle radiation in the downslope direction. But Moxon also shows specifically that there are *no* such advantages for vertical polarization. The ground-reflected ray is lost at a high angle. |
Hal Rosser wrote:
"Gary V. Deutschmann, Sr." wrote in message Several of them have their ground mounted HF antenna's perpendicular to the grade.. That vertical must be *downhill* from the house - else loss of sleep will occur. And wouldn't the uphill guy wires need to be doubled up ? Does the term 'uphill' guys imply that there are 'downhill' guys? Would they be required? Be careful not to confuse the term 'downhill guys' with old hams. Irv VE6BP -------------------------------------- Diagnosed Type II Diabetes March 5 2001 Beating it with diet and exercise! 297/215/210 (to be revised lower) 58"/43"(!)/44" (already lower too!) -------------------------------------- Visit my HomePage at http://members.shaw.ca/finkirv/index.html Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm -------------------- Irv Finkleman, Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP Calgary, Alberta, Canada |
chuck wrote:
Intuitively, and looking at Moxon's sketch, it would seem that the effect would be simply to rotate the vertical pattern by the amount of the slope. Aiming the pattern "down the slope" rather than "toward the horizon" does not seem to be a necessarily worse situation as Moxon suggests. Wouldn't that actually put more energy out toward the horizon? That is true in principle, but the problem with a ground-mounted vertical antenna is that the angle of maximum radiation is fixed in relation to the ground. That means the angle of the slope has to be just right, and in general it also needs to be very steep. With a horizontal antenna, you can vary the angle of maximum radiation by adjusting the height above ground. That makes it easy to apply the technique over a wide range of quite moderate slope angles, using quite modest antenna heights. Changing the subject slightly, hams have become over-conditioned into wanting a "low" angle of radiation. It's true that we generally do need more radiation at lower angles than we can easily achieve; but until recently, we haven't had the information to understand what angles of radiation we actually *do* need. Modern HF propagation programs give us that information. Not surprisingly, the optimum angle varies according to the path, the number of hops involved, the heights of the respective layers and the ionization levels... and hence the optimum angle also depends on the time of day, the season, and the year in the sunspot cycle. Recent editions of the ARRL Antenna Handbook analyse this problem in some detail, and show that "lowest possible angle" is not always the best objective if you're aiming to cover all possible cases. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
"chuck" wrote in message nk.net... Hello Gary, Don't know from personal experience, but Les Moxon, author of HF Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. ==================================== What makes you think he is more right than anybody else? Why should you be a judge? Why do you seek support from paid book writers? Do you lack confidence in your personal judgement and statements? This small, slightly critical, message is intended to be in the most friendly of terms. Applicable to many others in these threads. I wish you the all best of both local stations and DX. And, as the festive season approaches, an enjoyable Xmas holiday for both you and your family. ---- Reg. |
Don't know from personal experience, but Les Moxon, author of HF
Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. The advantages of which Moxon wrote are for *horizontal* polarization only. If the antenna height above ground is correct, the ground reflection can reinforce low-angle radiation in the downslope direction. But Moxon also shows specifically that there are *no* such advantages for vertical polarization. The ground-reflected ray is lost at a high angle. -- 73 from Ian G3SEK ================================== Dear Ian, what has Moxon got to do with it? Without personal experience how do you know you are not plagiarising and further propagating old-wives' tales? If you have personal experience do you need anybody else's support anyway? Just state the facts on your own authority. Or do authors all belong to the same masonic club which adds nothing to veracity? My only little axe is that I find it irritating when I read about quite unnecessary references which add nothing but verbiage to the conversation. Perhaps I'm funny or just impatient in that way. But I'm sure you understand my non-technical interruption to this thread with my appology. Reply not needed. (PS: I have only vaguely heard of Moxon in these newsgroups. Never read him. Not the slightest disrespect to him, or her, intended. But my own reference bibles are restricted to Ohm, Ampere and Volta.) ---- I think I can still call you my Internet friend. ;o) ---- Yours, Reg, G4FGQ |
Does the term 'uphill' guys imply that there are 'downhill' guys? Would
they be required? Be careful not to confuse the term 'downhill guys' with old hams. Quite right! One should not confuse the term "over the hill" with "downhill" :-) --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.799 / Virus Database: 543 - Release Date: 11/19/2004 |
Reg Edwards wrote:
Don't know from personal experience, but Les Moxon, author of HF Antennas for all Locations, seems to believe it creates an advantage. You might want to read his thoughts on that. The advantages of which Moxon wrote are for *horizontal* polarization only. If the antenna height above ground is correct, the ground reflection can reinforce low-angle radiation in the downslope direction. But Moxon also shows specifically that there are *no* such advantages for vertical polarization. The ground-reflected ray is lost at a high angle. -- 73 from Ian G3SEK ================================== Dear Ian, what has Moxon got to do with it? He was the person who was being misquoted. In the first reply, I was setting that record straight. Without personal experience how do you know you are not plagiarising and further propagating old-wives' tales? Because, whatever else I read, I also do my own thinking. If you have personal experience do you need anybody else's support anyway? Just state the facts on your own authority. Or do authors all belong to the same masonic club which adds nothing to veracity? Certainly not; most authors do value a cross-check on their own thinking - and above all, a cross-check against reality. I certainly do, because it's how I was trained. The value of the major academic textbooks is that most of them have been in the public domain for decades, and available for critique and cross-checking and correction in later editions. If your own findings don't agree with the pool of knowledge that's already out there, you'd better have some strong reasons to hand. In this respect, all amateur radio publications are in a lesser league. They are still going through the process of critique and technical clarification - marvellously accelerated by the Internet in recent years - but they're not there yet. (PS: I have only vaguely heard of Moxon in these newsgroups. Never read him. Not the slightest disrespect to him, or her, intended. Perhaps you should: Moxon was a lot like you in his methods and his ways of thinking. But my own reference bibles are restricted to Ohm, Ampere and Volta.) All three of whom are conveniently not available for comment. ---- I think I can still call you my Internet friend. ;o) ---- For about 15 hours out of 24, I reckon. But anytime after your first glass of the evening, and before my first cup of coffee the next day, don't push your luck :-) -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
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