|
Mostly horizontal polarization of HF arriving at my antenna?
I have an inverted-V, approximately resonant on 40, 20, 15 and 10m.
I have tried numerous verticals for comparison, but on these bands the inverted-V always receives signals on these bands better or equally well, at best. The verticals have been well grounded (using a "large, good quality" metal sheet roof as the ground) and I have done my best to minimize losses. The verticals have been anywhere from 1/4 to 5/8 wavelengths long. But they are always outperformed by my inv-V on these bands. Only on 80 and 160m are the verticals better. Now, this leads me to wondering if the radio waves arriving at my QTH tend to be largely horizontally polarized on the higher frequencies? Or can there be any other explanation that "good" verticals, even 5/8 wavelengths long are never better than the inv-V. Any thoughts? The verticals and the inv-V were all mounted on the metal roof of my house. The house is located in a poor-quality ground area (rocks, shallow vegetation), the direction to Europe is across a low hill approx. 1/2 mile away while the direction to America is across the open sea approx. 1/8 mile away from my house. 73 - Kristinn, TF3KX |
I had a wilson 4 band verticle mounted on top of a 30 foot tower with
4 radials run out for each band, in short if I could hear 'em I could work 'em. It was that simple........ Noise seems to be more pronounced with verticle polarization. I did have a 40M inverted vee on that tower as well and used to switch between the antennas. Since I was on the west coast at the time, the east coasters were stronger on the verticle than the inverted vee. I would in NO way say my tests were very scientific, just looked at the S meter readings. Yes it was an actual meter movement (IC-720) had one. I hope this helps you in some way with what you are trying to accomplish. John "Kristinn Andersen, TF3KX" wrote in message om... I have an inverted-V, approximately resonant on 40, 20, 15 and 10m. SNIP Now, this leads me to wondering if the radio waves arriving at my QTH tend to be largely horizontally polarized on the higher frequencies? Or can there be any other explanation that "good" verticals, even 5/8 wavelengths long are never better than the inv-V. Any thoughts? 73 - Kristinn, TF3KX |
HF signals are usually not predominantly polarized more horizontal or
vertical. The effect that you are seeing is due to the effective height of the dipole above ground. On 40,20,15,10 the dipole is high enough (in terms of wavelengths) that it develops a good pattern at lower angles of radiation (or reception). On 80 and 160 meters, your dipole is too close to the ground for it to have a good low-angle pattern. Thus what you are seeing is that the signals you want to listen to are arriving at an angle lower than what your 80/160 meter dipoles are effective at. The vertical antenna has a lower angle of reception on these bands than the dipole. If you listen to signals out to ~300 km on 80 meters, you may find that your dipole outperforms the vertical because those signals are arriving at your antenna from a fairly high angle. -- Tom "Kristinn Andersen, TF3KX" wrote in message om... I have an inverted-V, approximately resonant on 40, 20, 15 and 10m. I have tried numerous verticals for comparison, but on these bands the inverted-V always receives signals on these bands better or equally well, at best. The verticals have been well grounded (using a "large, good quality" metal sheet roof as the ground) and I have done my best to minimize losses. The verticals have been anywhere from 1/4 to 5/8 wavelengths long. But they are always outperformed by my inv-V on these bands. Only on 80 and 160m are the verticals better. Now, this leads me to wondering if the radio waves arriving at my QTH tend to be largely horizontally polarized on the higher frequencies? Or can there be any other explanation that "good" verticals, even 5/8 wavelengths long are never better than the inv-V. Any thoughts? The verticals and the inv-V were all mounted on the metal roof of my house. The house is located in a poor-quality ground area (rocks, shallow vegetation), the direction to Europe is across a low hill approx. 1/2 mile away while the direction to America is across the open sea approx. 1/8 mile away from my house. 73 - Kristinn, TF3KX |
Tom: I agree with you on the 160/80m explanation for the better
performance of the vertical than the inv-V. Generally it is assumed that polarization of arriving HF signals is randomly oriented and constantly changing - which I have no grounds to refute. Thus, your suggestion that my inv-V (horizontal antenna) is simply gaining advantage from its height (and in some cases azimuthal directivity) is a viable explanation. Keep in mind that the inv-V is supported by an aluminum pole with an apex 6m (18ft) above my metallic roof, and the roof itself is at 8m (24ft) above the surrounding ground - thus the apex point is at 14m (42ft) above ground. It just struck me that even the "supposedly best" verticals (5/8 wl, using good connections to the metal roof as a counterpoise) are consistently substantially weaker on reception on 40-10m than the inv-V. The difference varies from zero to 7-8 S-units. I would have expected the vertical to be better in at least a few cases - but it's not. But, OK - the inv-V dipole is gaining further from its height. Any other suggestions, anyone? 73 - Kristinn, TF3KX "TOM" wrote in message news:7P%Yd.1796$oa6.1254@trnddc07... HF signals are usually not predominantly polarized more horizontal or vertical. The effect that you are seeing is due to the effective height of the dipole above ground. On 40,20,15,10 the dipole is high enough (in terms of wavelengths) that it develops a good pattern at lower angles of radiation (or reception). On 80 and 160 meters, your dipole is too close to the ground for it to have a good low-angle pattern. Thus what you are seeing is that the signals you want to listen to are arriving at an angle lower than what your 80/160 meter dipoles are effective at. The vertical antenna has a lower angle of reception on these bands than the dipole. If you listen to signals out to ~300 km on 80 meters, you may find that your dipole outperforms the vertical because those signals are arriving at your antenna from a fairly high angle. -- Tom "Kristinn Andersen, TF3KX" wrote in message om... I have an inverted-V, approximately resonant on 40, 20, 15 and 10m. I have tried numerous verticals for comparison, but on these bands the inverted-V always receives signals on these bands better or equally well, at best. The verticals have been well grounded (using a "large, good quality" metal sheet roof as the ground) and I have done my best to minimize losses. The verticals have been anywhere from 1/4 to 5/8 wavelengths long. But they are always outperformed by my inv-V on these bands. Only on 80 and 160m are the verticals better. Now, this leads me to wondering if the radio waves arriving at my QTH tend to be largely horizontally polarized on the higher frequencies? Or can there be any other explanation that "good" verticals, even 5/8 wavelengths long are never better than the inv-V. Any thoughts? The verticals and the inv-V were all mounted on the metal roof of my house. The house is located in a poor-quality ground area (rocks, shallow vegetation), the direction to Europe is across a low hill approx. 1/2 mile away while the direction to America is across the open sea approx. 1/8 mile away from my house. 73 - Kristinn, TF3KX |
|
Kristinn:
A poorly performing vertical is usually traced to an inadequate ground system, which reduces it's efficiency. Less often, it could also be caused by an electrically shortened antenna, which can experience poor efficiency. Assuming approximately one quarter wavelength for each radial, on 40 m you would want quite a few 10 meter long radials; the plot of land needed is in the order of 310 square meters. A metal roof may or may not prove to be a useful ground reference. There are a lot of things that can go wrong. A 5/8 wavelength vertical achieves gain by pattern enhancement at lower radiation angles and sacrificing signals at higher elevation angles. If you have poor ground (in the near field) or poor ground conductivity/dielectric constant (in the not-so-near field) you probably will not be able to realize this gain. My experience with 5/8 wave verticals on HF is that they did not work as well as anticipated. If the arrival angle of the HF signal is higher than the lobe of the vertical antenna, then 'gain' has hurt, not helped. A properly designed 4-square vertical antenna system over a good ground radial system will perform very well on 40 meters for DX. The Hy-Gain Hytower vertical antenna with a good quality ground radial system has proven to perform reasonably well on HF. -- Tom "Kristinn Andersen, TF3KX" wrote in message om... Tom: I agree with you on the 160/80m explanation for the better performance of the vertical than the inv-V. Generally it is assumed that polarization of arriving HF signals is randomly oriented and constantly changing - which I have no grounds to refute. Thus, your suggestion that my inv-V (horizontal antenna) is simply gaining advantage from its height (and in some cases azimuthal directivity) is a viable explanation. Keep in mind that the inv-V is supported by an aluminum pole with an apex 6m (18ft) above my metallic roof, and the roof itself is at 8m (24ft) above the surrounding ground - thus the apex point is at 14m (42ft) above ground. It just struck me that even the "supposedly best" verticals (5/8 wl, using good connections to the metal roof as a counterpoise) are consistently substantially weaker on reception on 40-10m than the inv-V. The difference varies from zero to 7-8 S-units. I would have expected the vertical to be better in at least a few cases - but it's not. But, OK - the inv-V dipole is gaining further from its height. Any other suggestions, anyone? 73 - Kristinn, TF3KX "TOM" wrote in message news:7P%Yd.1796$oa6.1254@trnddc07... HF signals are usually not predominantly polarized more horizontal or vertical. The effect that you are seeing is due to the effective height of the dipole above ground. On 40,20,15,10 the dipole is high enough (in terms of wavelengths) that it develops a good pattern at lower angles of radiation (or reception). On 80 and 160 meters, your dipole is too close to the ground for it to have a good low-angle pattern. Thus what you are seeing is that the signals you want to listen to are arriving at an angle lower than what your 80/160 meter dipoles are effective at. The vertical antenna has a lower angle of reception on these bands than the dipole. If you listen to signals out to ~300 km on 80 meters, you may find that your dipole outperforms the vertical because those signals are arriving at your antenna from a fairly high angle. -- Tom "Kristinn Andersen, TF3KX" wrote in message om... I have an inverted-V, approximately resonant on 40, 20, 15 and 10m. I have tried numerous verticals for comparison, but on these bands the inverted-V always receives signals on these bands better or equally well, at best. The verticals have been well grounded (using a "large, good quality" metal sheet roof as the ground) and I have done my best to minimize losses. The verticals have been anywhere from 1/4 to 5/8 wavelengths long. But they are always outperformed by my inv-V on these bands. Only on 80 and 160m are the verticals better. Now, this leads me to wondering if the radio waves arriving at my QTH tend to be largely horizontally polarized on the higher frequencies? Or can there be any other explanation that "good" verticals, even 5/8 wavelengths long are never better than the inv-V. Any thoughts? The verticals and the inv-V were all mounted on the metal roof of my house. The house is located in a poor-quality ground area (rocks, shallow vegetation), the direction to Europe is across a low hill approx. 1/2 mile away while the direction to America is across the open sea approx. 1/8 mile away from my house. 73 - Kristinn, TF3KX |
It just struck me that even the "supposedly best" verticals (5/8 wl,
using good connections to the metal roof as a counterpoise) are consistently substantially weaker on reception on 40-10m than the inv-V. The difference varies from zero to 7-8 S-units. I would have expected the vertical to be better in at least a few cases - but it's not. ....................................... The *best* 5/8 wave antennas would not use a roof as the ground plane. I think this is half the problem. You are running an elevated vertical, "ground plane", but your radial system is not resonant. This would greatly effect the performance of most all the various length radiators. Then you have to consider the construction of the roof, how well each piece is electrically connected, etc, etc..Then you mention the poor overall ground rating for your local in general. This all combines for a mediocre antenna. Then on top of that, you have to consider the height above ground in wavelengths, for each particular band, and the efficiency for each band. Naturally, the lower bands would see the most ground losses, from the low height. I can see a 5/8 antenna for 10m being fairly poor, when mounted on a untuned roof. In a case like that, you should use an elevated antenna, with elevated radials above the roof. Or, use a 1/2 wave which requires no radials. On the lower bands, I think the performance is probably not so good, due to the ground system not being near as good as you think it is. Being elevated, it really should be resonant for each band to be used. I can see it being a toss on 20m up, but on 40m, and lower, the vertical should be best for dx. "over 1500 miles" If it's not, it's not working as well as it could. MK |
| All times are GMT +1. The time now is 09:02 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com