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Incoming radiation angles
Looking for a site or information on incoming
radiation angles specifically for 160 metres. 1 How is it measured ? 1a Can it discriminate between vertical and horizontal or what ever polarisation 2 What is the angles per percentage of contacts 3 Are they all horizontally polarised when subject to skip? for distances over say 1000 miles distance One well known DXer (Tom) stated on this newsgroup that a horizontal dipole at 1/2 wave length was inferior to his other antennas, but no specifics given! Appreciate any pointers on the above. Happy New Year Art |
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In message , Art Unwin
KB9MZ writes Looking for a site or information on incoming radiation angles specifically for 160 metres. 1 How is it measured ? The same way it was measured in the 20's for B/C reception. Two separated antennas at different heights feeding an oscilloscope to produce an ellipse. The phase difference between the antennas allows the angle to be calculated. Mike -- M.J.Powell |
Art, K9MZ wrote:
"---radiation angles specifically for 160 meters. 1. How is it measured?" In degrees above the horizon. It`s geometrical. The effective height of the reflecting layer above the earth has been observed for a long time and can be predicted with some accuracy, based upon location, time, solar radiation, etc. The angle of incidence is equal to the angle of reflection to a reference normal to the reflecting plane. So, low angles serve for long distances between stations, and high angles for short distances that are too distant to be reached by the groundwave. Capt. Paul H. Lee, USNR, K6TS has a chart of degrees above the horizon versus distance to the first reflection zone (a single hop) on page 11 of "Vertical Antenna Handbook", a "CQ" publication. As the height of the latyer is variable, this is an approximation based on probabilities. A 5/8-wave vertical gives optimum low-angle radiation between 3 and 27 degrees. The latter angle gets you out to about 500 miles. Lower angles get you out to about 2000 miles on one hop. Vertical antennas work with vertically polarized waves. Once the wave is reflected by the ionosphere, polarization of the reflection is more or less random. "2. What is the angles per percentage of contacts?" Depends on where your station is in respect to the majority of stations you want to contact. "3. Are they all horizontally polarized when subject to skip?" No. The ionosphere does not care what the wave polarization is. It will reflect whatever strikes it at various polarizations. It won`t maintain polarizations! You can receive via the ionosphere almost equally well, on average, with any polarization regardless of what was transmitted. Noise reception is likely worse using a vertical receiving antenna. "Tom stated on this newsgroup that a horizontal dipole at 1/2-wavelength was inferior to his other antennas---." Can`t argue with Tom`s observation about his antennas, but it does not correspond with most observations of horizontal antenna performance when you have a resonant dipole at 1/2-wave above the earth. Look at Fig 12-D on page 3-11 of the 19th edition of the ARRL Antenna Book. Maximum radiation is at 30-degrees above the horizon. From Capt. Lee`s diagram, that would get you stations as close as 500 miles, and beyond 1000 miles due to the range of strong elevation angles in the pattern. I don`t know what Ton`s problems are but suspect that he ignores some of the ground effects. He has expressed dissatisfaction with his verticals too. Vertivcals in particular are sensitive to good earth under and around the antenna. Horizontal polarization isn`t bad for HF. Most of the world`s HF commercial stations use horizontal antennas for skywave propagation. Best regards, Richard Harrison, KB5WZI |
Incoming radiation angles can be obtained by geometric calculation.
Pythagorus and all that, taking earth curvature, height of ionospheric layers, number of hops, etc, etc, into account. Then point your receiving beam into it, if it is adjustable in the vertical plane. Very non-critical. Antenna apperture angles in the vertical plane are extremely broad. The stuff often comes in from more than one angle. Interference between the different paths causes fading and distortion. An antenna will collect from all vertical angles regardles of elevation. ---- Reg =================== "Art Unwin KB9MZ" wrote in message m... Looking for a site or information on incoming radiation angles specifically for 160 metres. 1 How is it measured ? 1a Can it discriminate between vertical and horizontal or what ever polarisation 2 What is the angles per percentage of contacts 3 Are they all horizontally polarised when subject to skip? for distances over say 1000 miles distance One well known DXer (Tom) stated on this newsgroup that a horizontal dipole at 1/2 wave length was inferior to his other antennas, but no specifics given! Appreciate any pointers on the above. Happy New Year Art |
"Richard Harrison" wrote in message ... Art, K9MZ wrote: "---radiation angles specifically for 160 meters. 1. How is it measured?" In degrees above the horizon. It`s geometrical. The effective height of the reflecting layer above the earth has been observed for a long time and can be predicted with some accuracy, based upon location, time, solar radiation, etc. Where can I see these predictions for the present time? The angle of incidence is equal to the angle of reflection to a reference normal to the reflecting plane. So, low angles serve for long distances between stations, and high angles for short distances that are too distant to be reached by the groundwave. Understood Capt. Paul H. Lee, USNR, K6TS has a chart of degrees above the horizon versus distance to the first reflection zone (a single hop) on page 11 of "Vertical Antenna Handbook", a "CQ" publication. As the height of the latyer is variable, this is an approximation based on probabilities. I will pull that one out. A 5/8-wave vertical gives optimum low-angle radiation between 3 and 27 degrees. The latter angle gets you out to about 500 miles. Lower angles get you out to about 2000 miles on one hop. O.K. Vertical antennas work with vertically polarized waves. Once the wave is reflected by the ionosphere, polarization of the reflection is more or less random. Hmm, so a vertical tho low angle would miss out on horizontal polarisations which leaves a lot of unknown with respect to best antenna for Top band "2. What is the angles per percentage of contacts?" Depends on where your station is in respect to the majority of stations you want to contact. Over 1000 miles "3. Are they all horizontally polarized when subject to skip?" No. The ionosphere does not care what the wave polarization is. It will reflect whatever strikes it at various polarizations. It won`t maintain polarizations! You can receive via the ionosphere almost equally well, on average, with any polarization regardless of what was transmitted. Well I thought that kmost transmitions changed to horizontal after reflection! Noise reception is likely worse using a vertical receiving antenna. Well I am confused about that My present rotatable dipole at a 'low" height matches a beverage at 15 degrees but unfortunately the gain continues to a max at 90 degrees where as the beverage whereas the beverage nulls out the higher angles which ius why I presume it was chosen as a listening antenna. "Tom stated on this newsgroup that a horizontal dipole at 1/2-wavelength was inferior to his other antennas---." Can`t argue with Tom`s observation about his antennas, but it does not correspond with most observations of horizontal antenna performance when you have a resonant dipole at 1/2-wave above the earth. Look at Fig 12-D on page 3-11 of the 19th edition of the ARRL Antenna Book. Maximum radiation is at 30-degrees above the horizon. From Capt. Lee`s diagram, that would get you stations as close as 500 miles, and beyond 1000 miles due to the range of strong elevation angles in the pattern. I don`t know what Ton`s problems are but suspect that he ignores some of the ground effects. He has expressed dissatisfaction with his verticals too. Vertivcals in particular are sensitive to good earth under and around the antenna. Horizontal polarization isn`t bad for HF. Most of the world`s HF commercial stations use horizontal antennas for skywave propagation. Well I have put my dipole in the vertical position also which negates use of radials but I have not noticed any profound differences as yet after a few days ! This new band to me is raising a lot of questions for me that I haven't thought of before so I am at a new horizon and without the spirit level as the bubble has burst. Cheers Art band Best regards, Richard Harrison, KB5WZI |
"Reg Edwards" wrote in message ...
Incoming radiation angles can be obtained by geometric calculation. Pythagorus and all that, taking earth curvature, height of ionospheric layers, number of hops, etc, etc, into account. Then point your receiving beam into it, if it is adjustable in the vertical plane. Very non-critical. Antenna apperture angles in the vertical plane are extremely broad. The stuff often comes in from more than one angle. Interference between the different paths causes fading and distortion. An antenna will collect from all vertical angles regardles of elevation. ---- Reg =================== Interesting thing happened with the antenna last night. Had the antenna in the vertical position close to ground ( it is a truncated co linear dipole) And was prevented from joining the local group because of multiple QSOs on the same frequency! Art |
AArt, KB9MZ wrote:
"Where can I see these predictions for the present time?" Inquire of the National Institute of Science and Technology for propagation forecasts. (Your tax dollars at work) The National Bureau of Standards used to broadcast a limited amount of propagation forecasts on WWV. Haven`t listened in a long time, so don`t know what`s on WWV now. NBS also made available extensive propagation forecast information for the world, by mail, on a subscriotion basis. Best regards, Richard Harrison, KB5WZI |
Art, KB9MZ wrote:
"And was prevented from joining the local group because of nultiple QSOs on the same frequency." Single-element vertical antennas are deficient in directivity at any azimuth. They have a single null off their tips, that is toward the zenith. At HF, groundwave disappears with increasing frequency. Thus, short range communication is hindered. Best regards, Richard Harrison, KB5WZI |
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