|
HFTA-ARRL-Space
Tried to make the subject grab a bit.
I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There are HFTA graphs showing elevation response for various antenna configurations (mostly Yagis). Most arrays show good response up to 12 degrees above the horizon, then many show a null and then, a second peak around 25 to 30 degrees above the horizon. Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? Am I right to consider this component of propagation to have left the earth? This would indicate a substantial fraction of each amateur transmission is sent into space. I always thought Broadcast transmissions were most likely to emanate from Earth. Are hams more or less likely to transmit into space than Broadcast? John (who wishes to remain a student and never an expert) |
HFTA-ARRL-Space
On Sat, 01 Jul 2006 11:09:22 -0400, jawod wrote:
Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? In your HFTA program run the antennas at various heights. Amongst other things,varying the height of the antenna will change the elevation angle of the lobes. Danny, K6MHE |
HFTA-ARRL-Space
On Sat, 01 Jul 2006 11:09:22 -0400, jawod wrote:
Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? Hi John, You are confusing models of propagation with models for antenna lobe characteristics. The lobes certainly have a major impact on propagation, but the antenna modeler is not concerned with that. The terrain modeler is not a propagation modeler. For that, consult VOACAP or WINCAP. They are properly concerned with ionospheric issues, but they are also driven by antenna models too. Am I right to consider this component of propagation to have left the earth? To some degree, yes, but it has very little bearing on what you are focused on here. This would indicate a substantial fraction of each amateur transmission is sent into space. In fact, no. The apportionment of the energy into lobes is simply robbing Peter to pay Paul. The nulls were developed from energy lost to the peaked lobes. This is very loose analogy because energy was never lost, it is merely the combination from many sources that makes this lobe shape appears as it does. An antenna radiates from every portion of its structure and in every direction. When all contributions are viewed from a distance, some portions of the structure are out of phase with respect to others portions. When those two contributions are 180° out of phase, that remote point at where they combine perceives a null (a destructive combination). At some other remote point, those same two contributions may combine constructively for a peak response. Same energies all around, but path lengths shift the wave phases and how they combine constructs the characteristic lobe shape. If you took college physics, you must have seen how two charges separated by a distance combine their effects at remote points to offer an "electric dipole." Same logic. 73's Richard Clark, KB7QHC |
HFTA-ARRL-Space
Whether you call it Refraction or Reflection hardly matters.
What matters is that the wave, in effect, is reflected from an ionospheric layer at at a particular height, roughly according to optical laws. Trigonometry Rules! Since the transmitted 'beam' has a very wide angle in the vertical plane, the energy returns to earth over an even wider range of distances. The 'elevation angle' reported by antenna simulation programs is not very meaningfull. It contains very little useful information, mainly because the height of a reflecting layer is unknown at the time of transmission. Neither is the number of hops known to a particular destination. ---- Reg. |
HFTA-ARRL-Space
Hi Richard,
It's good to see you are NOT using Queen Elizabeth the First's, Shakespear's poetical, but somewhat difficult to understand language. Inapropriate for technical matters. There must be other newsgroups available to people who enjoy writing sonnets. As we always knew by reading, with difficulty, between the lines, you are an exceptionally knowledgeable person. Please keep up the good work by continuing to use modern American English, as demonstrated in your last valuable contribution. Thank you. ---- Yours, Punchinello |
HFTA-ARRL-Space
On Sat, 1 Jul 2006 18:15:01 +0100, "Reg Edwards"
wrote: It's good to see you are NOT using Queen Elizabeth the First's, Shakespear's poetical, but somewhat difficult to understand language. Hi Reggie, I reserve that for the technical Falstaffs. Inapropriate for technical matters. Their usual plea is "discretion is the better part of a direct answer...." As such, technical matters are notably absent, or at best serving as a stalking horse. For those who are shy in their English skills, "stalking horse" finds its current usage in "trolling." 73's Richard Clark, KB7QHC |
HFTA-ARRL-Space
Richard,
I have NEVER considered your contributions to be deliberate trolling. You just can't help mixing up your desire to produce poetry with your desite to spread technical enlightonment. The two don't mix very well. I am 3/4 of the way down a bottle of "Cotes du Rhone Villages" red, 2004, 14.5% by volume. (I have a great liking for our near neighbours, the French.) So please excuse me if my psycho-analysis is not exactly as you might perceive it yourself. ---- Yours, Punchinello. |
HFTA-ARRL-Space
"jawod" wrote in message ... Tried to make the subject grab a bit. I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There are HFTA graphs showing elevation response for various antenna configurations (mostly Yagis). Most arrays show good response up to 12 degrees above the horizon, then many show a null and then, a second peak around 25 to 30 degrees above the horizon. that is a function of height. the main lobe from the antenna is aimed at the horizon and there are other lobes from the design of then antenna. then reflections from the ground cause more vertical variations. these are dependent on the height and the terrain around the antenna. Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? not necessarily. look at the arrival angle statistics and you will see that frequently very high angle propagation is possible. usually higher angles mean shorter distances but at times you can get many short high angle hops to cover long distances also. Am I right to consider this component of propagation to have left the earth? This would indicate a substantial fraction of each amateur transmission is sent into space. I always thought Broadcast transmissions were most likely to emanate from Earth. Are hams more or less likely to transmit into space than Broadcast? broadcast is more likely. there are many more broadcast stations on the air 24x7, over the same range of spectrum that we use, and running much higher power than we use. the most likely signals to reach out from earth are likely fm broadcast and tv signals since those are normally well above the critical frequency that reflects from the ionosphere and can be fairly high power. lower hf, mf, and lf are less likely to get out as they reflect from the ionosphere even at very high angles. John (who wishes to remain a student and never an expert) |
HFTA-ARRL-Space
Dear John:
If you were a radio amateur who is interested in working other radio amateurs at a great distance, then you wish to have a significant portion of your antenna's radiation within about 12 to 2 degrees above the horizon. In tern, this goal suggests that a preferred height for an HF, horizontally-polarized antenna is between 2 and 2.5 wavelengths above ground. If the higher angle radiation does not pass through the ionosphere, it contributes to interference to (relatively) nearby stations (and, because the antenna probably is used for reception, contributes to hearing nearby stations). Expensive HF antenna systems exist that significantly suppress all except the lowest lobe. If you wish to be a student of antennas, do invest in Kraus' 3rd edition of Antennas. Read and study the book starting with the first chapter. Regards, Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "jawod" wrote in message ... Tried to make the subject grab a bit. I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There are HFTA graphs showing elevation response for various antenna configurations (mostly Yagis). Most arrays show good response up to 12 degrees above the horizon, then many show a null and then, a second peak around 25 to 30 degrees above the horizon. Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? Am I right to consider this component of propagation to have left the earth? This would indicate a substantial fraction of each amateur transmission is sent into space. I always thought Broadcast transmissions were most likely to emanate from Earth. Are hams more or less likely to transmit into space than Broadcast? John (who wishes to remain a student and never an expert) |
HFTA-ARRL-Space
On Sat, 1 Jul 2006 19:50:43 +0100, "Reg Edwards"
wrote: I am 3/4 of the way down a bottle of "Cotes du Rhone Villages" red, I've seen a varietal called "Goats do Roam" 2004, 14.5% by volume. YOW! (I have a great liking for our near neighbours, the French.) An empty bottle of Quadrupel "Three Philosophers" Belgian lambic ale (9.8%) sits nearby. So please excuse me if my psycho-analysis is not exactly as you might perceive it yourself. No, our both having included quantifiables from bench testing allows us to add to the topic. 73's Richard Clark, KB7QHC |
HFTA-ARRL-Space
Richard Clark wrote:
On Sat, 01 Jul 2006 11:09:22 -0400, jawod wrote: Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? Hi John, You are confusing models of propagation with models for antenna lobe characteristics. The lobes certainly have a major impact on propagation, but the antenna modeler is not concerned with that. The terrain modeler is not a propagation modeler. For that, consult VOACAP or WINCAP. They are properly concerned with ionospheric issues, but they are also driven by antenna models too. Am I right to consider this component of propagation to have left the earth? To some degree, yes, but it has very little bearing on what you are focused on here. This would indicate a substantial fraction of each amateur transmission is sent into space. In fact, no. The apportionment of the energy into lobes is simply robbing Peter to pay Paul. The nulls were developed from energy lost to the peaked lobes. This is very loose analogy because energy was never lost, it is merely the combination from many sources that makes this lobe shape appears as it does. An antenna radiates from every portion of its structure and in every direction. When all contributions are viewed from a distance, some portions of the structure are out of phase with respect to others portions. When those two contributions are 180° out of phase, that remote point at where they combine perceives a null (a destructive combination). At some other remote point, those same two contributions may combine constructively for a peak response. Same energies all around, but path lengths shift the wave phases and how they combine constructs the characteristic lobe shape. If you took college physics, you must have seen how two charges separated by a distance combine their effects at remote points to offer an "electric dipole." Same logic. 73's Richard Clark, KB7QHC Thanks for setting me right! John AB8WH |
HFTA-ARRL-Space
Richard Clark wrote:
On Sat, 1 Jul 2006 19:50:43 +0100, "Reg Edwards" wrote: I am 3/4 of the way down a bottle of "Cotes du Rhone Villages" red, snip 2004, 14.5% by volume. An empty bottle of Quadrupel "Three Philosophers" Belgian lambic ale (9.8%) sits nearby. snip 73's Richard Clark, KB7QHC While we're at it, I am just enjoying my first ever 20th Aniversary Summit Brewing Extra Special Bitter Ale. Just out this weekend. No %age listed. And not too bitter first taste, very smooth, light after bitter on the back of the tongue. Summit made another hit. tom K0TAR |
HFTA-ARRL-Space
Reg Edwards wrote:
Whether you call it Refraction or Reflection hardly matters. This I don't understand. To me, refraction versus reflection IS the issue. In optics, Brewster's angle is used. I still don't quite understand thte PseudoBrewster's Angle...it seems to have a different definition (at least in the ARRL book). What matters is that the wave, in effect, is reflected from an ionospheric layer at at a particular height, roughly according to optical laws. Trigonometry Rules! Since the transmitted 'beam' has a very wide angle in the vertical plane, the energy returns to earth over an even wider range of distances. The 'elevation angle' reported by antenna simulation programs is not very meaningfull. It contains very little useful information, mainly because the height of a reflecting layer is unknown at the time of transmission. Neither is the number of hops known to a particular destination. ---- Reg. Reg, Thanks for your answer. I guess I was trying to get at how much ham radio is propagated into space. Certainly SOME does. How does this compare to that amount propagated into space by Broadcast? My assumption has been that VHF TV, etc is easily passed through the ionosphere (minimally refracted). |
HFTA-ARRL-Space
Dave wrote:
broadcast is more likely. there are many more broadcast stations on the air 24x7, over the same range of spectrum that we use, and running much higher power than we use. the most likely signals to reach out from earth are likely fm broadcast and tv signals since those are normally well above the critical frequency that reflects from the ionosphere and can be fairly high power. lower hf, mf, and lf are less likely to get out as they reflect from the ionosphere even at very high angles. Radar is the best we do, but not much information is transmitted beyond the fact that we are here, the beam is usually narrow, and the direction varies quickly. EME is a distant 2nd, carries real information in simple codes, the direction varies slowly, the beamwidth is usually low (on high GHz bands it can be less than the width of the moon), and the number of transmitters is very low. Either one of the previous could be picked up from a fair distance, but not likely because of the narrow angles and varying direction. And commercial broadcasting doesn't have the ERP in any particular direction to carry far. We live next to a very large noise source that would tend to swamp out what we generate. tom K0TAR |
HFTA-ARRL-Space
Dave wrote:
"jawod" wrote in message ... Tried to make the subject grab a bit. I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There are HFTA graphs showing elevation response for various antenna configurations (mostly Yagis). Most arrays show good response up to 12 degrees above the horizon, then many show a null and then, a second peak around 25 to 30 degrees above the horizon. that is a function of height. the main lobe from the antenna is aimed at the horizon and there are other lobes from the design of then antenna. then reflections from the ground cause more vertical variations. these are dependent on the height and the terrain around the antenna. Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? not necessarily. look at the arrival angle statistics and you will see that frequently very high angle propagation is possible. usually higher angles mean shorter distances but at times you can get many short high angle hops to cover long distances also. Am I right to consider this component of propagation to have left the earth? This would indicate a substantial fraction of each amateur transmission is sent into space. I always thought Broadcast transmissions were most likely to emanate from Earth. Are hams more or less likely to transmit into space than Broadcast? broadcast is more likely. there are many more broadcast stations on the air 24x7, over the same range of spectrum that we use, and running much higher power than we use. the most likely signals to reach out from earth are likely fm broadcast and tv signals since those are normally well above the critical frequency that reflects from the ionosphere and can be fairly high power. lower hf, mf, and lf are less likely to get out as they reflect from the ionosphere even at very high angles. John (who wishes to remain a student and never an expert) Thanks to all for the "enlightenment". Guess I've got a little SETI streak in me. I just got back a copy of an Astrobiology text that I borrowed out. It's by Gilmour and Sephton, Cambridge University Press if anyone's interested. John |
HFTA-ARRL-Space
Tom Ring wrote:
Radar is the best we do, but not much information is transmitted beyond the fact that we are here, the beam is usually narrow, and the direction varies quickly. EME is a distant 2nd, carries real information in simple codes, the direction varies slowly, the beamwidth is usually low (on high GHz bands it can be less than the width of the moon), and the number of transmitters is very low. Either one of the previous could be picked up from a fair distance, but not likely because of the narrow angles and varying direction. And commercial broadcasting doesn't have the ERP in any particular direction to carry far. We live next to a very large noise source that would tend to swamp out what we generate. VHF and UHF emissions escalated rapidly after WWII with the popularization of TV, and these readily penetrate the ionosphere. So there's a sphere of such emissions radiating outward from the Earth at the speed of light. And at the leading edge of this radiation sphere are the McCarthy hearings and the Howdy Doody show. No wonder the ETs have left us alone! Roy Lewallen, W7EL |
HFTA-ARRL-Space
On Sat, 01 Jul 2006 11:09:22 -0400, jawod wrote:
Tried to make the subject grab a bit. I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There are HFTA graphs showing elevation response for various antenna configurations (mostly Yagis). Most arrays show good response up to 12 degrees above the horizon, then many show a null and then, a second peak around 25 to 30 degrees above the horizon. Here's my question: At 25 to 30 degrees elevation response, aren't these waves leaving the ionosphere (i.e., refracted instead of reflected)? Am I right to consider this component of propagation to have left the earth? This would indicate a substantial fraction of each amateur transmission is sent into space. I always thought Broadcast transmissions were most likely to emanate from Earth. Are hams more or less likely to transmit into space than Broadcast? John (who wishes to remain a student and never an expert) To: "Richard Clark" Subject: Please Post in rraa From: "Walter Maxwell" Date: Sat, 1 Jul 2006 17:31:29 -0400 Richard, I've been trying to post the msg below to the HFTA-ARRL-Space thread, but after three attempts to send it it doesn't get posted. Would you please post it for me in the spot following Mac's? Walt, W2DU Hello John, I believe your other respondents missed one of your points concerning reflection and refraction, and therefore didn't respond completely to it. Whether reflection, refraction, or total penetration of the ionosphere occurs depends on the ionospheric layer, the time of day that determines the sun angle on the layer, the resulting level of ionization, the angle the ray makes on incidence with the layer, and the frequency of the energy in the arriving ray. Consequently, the answer is complex. As we know, when the frequency is high enough (VHF and above) the result is total penetration--no reflection or refraction--line of sight reception only. On the other hand, at HF the ratio between reflection and refraction varies. There are times when both occur. During those times the portion of the incident ray that is reflected returns to earth, while the portion that is refracted continues on through the ionosphere into space and never returns. I'm not sufficiently knowledgeable on the subject to go into further detail, but now that they've been nudged, either Richard C or Reggie can. Or someone else more knowledgeable than I. Walt, W2DU |
HFTA-ARRL-Space
Roy Lewallen wrote:
VHF and UHF emissions escalated rapidly after WWII with the popularization of TV, and these readily penetrate the ionosphere. So there's a sphere of such emissions radiating outward from the Earth at the speed of light. And at the leading edge of this radiation sphere are the McCarthy hearings and the Howdy Doody show. No wonder the ETs have left us alone! Roy Lewallen, W7EL What was wrong with Howdy Doody? tom K0TAR |
HFTA-ARRL-Space
On Sat, 01 Jul 2006 16:11:42 -0700, Richard Clark
wrote: On the other hand, at HF the ratio between reflection and refraction varies. There are times when both occur. During those times the portion of the incident ray that is reflected returns to earth, while the portion that is refracted continues on through the ionosphere into space and never returns. I'm not sufficiently knowledgeable on the But is it actually reflection? Owen -- |
HFTA-ARRL-Space
On Sat, 01 Jul 2006 18:32:46 -0400, jawod wrote:
This I don't understand. To me, refraction versus reflection IS the issue. In optics, Brewster's angle is used. I still don't quite understand thte PseudoBrewster's Angle...it seems to have a different definition (at least in the ARRL book). Hi John, Perhaps you should offer that definition as its application seems to be quite rare, and paired with some obscurity to the world of sub-atomic dispersion. I guess I was trying to get at how much ham radio is propagated into space. Certainly SOME does. SOME about covers it (you want that specified in dB?). I suppose by your other references to SETI you are wondering about the chances of a QSO in the same frequency from the other side of that ionospheric curtain. Given the odds, one frequency is as good as the next.... How does this compare to that amount propagated into space by Broadcast? There you have to consider the magnitude of flux, continuously, over the years. If the broadcasting is from Fox news (or any Murdoch source for that matter), it will be indistinguishable from pinko noise. 73's Richard Clark, KB7QHC |
HFTA-ARRL-Space
"Owen Duffy" wrote in message ... On Sat, 01 Jul 2006 16:11:42 -0700, Richard Clark wrote: On the other hand, at HF the ratio between reflection and refraction varies. There are times when both occur. During those times the portion of the incident ray that is reflected returns to earth, while the portion that is refracted continues on through the ionosphere into space and never returns. I'm not sufficiently knowledgeable on the But is it actually reflection? no, it is actually a refraction. but it is useful sometimes to model it as a reflection from a slightly higher level. that makes computation of angles of incidence and height a bit easier. |
HFTA-ARRL-Space
But is it actually reflection? no, it is actually a refraction. but it is useful sometimes to model it as a reflection from a slightly higher level. that makes computation of angles of incidence and height a bit easier. ============================================ The trigonometry is quite simple. Things become complicated when the reflecting layer is not horizontal, ie., the layer is tilted. The angle and direction of tilt are very difficult to predict. Consequently, where on the surface of the Earth a ray returns is anybody's guess. This makes the vertical take-off angle, reported by antenna modelling programs, even less useful. ---- Reg. |
HFTA-ARRL-Space
"Reg Edwards" wrote in message ... But is it actually reflection? no, it is actually a refraction. but it is useful sometimes to model it as a reflection from a slightly higher level. that makes computation of angles of incidence and height a bit easier. ============================================ The trigonometry is quite simple. Things become complicated when the reflecting layer is not horizontal, ie., the layer is tilted. The angle and direction of tilt are very difficult to predict. Consequently, where on the surface of the Earth a ray returns is anybody's guess. This makes the vertical take-off angle, reported by antenna modelling programs, even less useful. no, it doesn't make it less useful. as a statistic it is still good, but you have to remember that it is nothing more than a statistic. and everyone knows 'you can prove anything with statistics'. the fact that the ionosphere is more complicated than a horizontal reflection layer model represents doesn't mean that its usefulness is reduced, just that there are some cases when it won't be completely accurate... those are the fun things that happen with propagation that keep it interesting. |
HFTA-ARRL-Space
Dear Reg:
You have articulated one of the many reasons why HF propagation is described in stochastic terms. As you know very well, measurements or predictions comprise at least two numbers: the best estimate of the number and an estimate of the uncertainty of the first number. Present models of HF propagation, which include antenna characteristics, provide both numbers. Early models of HF propagation tended to be somewhat deficient in providing the second number. However, I remember using the early models to predict (extrapolate) in real-time how much longer a certain frequency was likely to remain usable from noting the drop-out of a higher frequency. The physics involved has been understood for many years. It takes a long period of data gathering to be able to do a good job with the second number. In the early days (post WW2) of radio astronomy, the uncertainties of some important measurements were greater than the estimate. That did not last. 73 Mac N8TT P.S. Nice to know that W2DU is back. -- J. Mc Laughlin; Michigan U.S.A. Home: "Reg Edwards" wrote in message ... But is it actually reflection? no, it is actually a refraction. but it is useful sometimes to model it as a reflection from a slightly higher level. that makes computation of angles of incidence and height a bit easier. ============================================ The trigonometry is quite simple. Things become complicated when the reflecting layer is not horizontal, ie., the layer is tilted. The angle and direction of tilt are very difficult to predict. Consequently, where on the surface of the Earth a ray returns is anybody's guess. This makes the vertical take-off angle, reported by antenna modelling programs, even less useful. ---- Reg. |
HFTA-ARRL-Space
Richard Clark wrote:
On Sat, 01 Jul 2006 18:32:46 -0400, jawod wrote: This I don't understand. To me, refraction versus reflection IS the issue. In optics, Brewster's angle is used. I still don't quite understand thte PseudoBrewster's Angle...it seems to have a different definition (at least in the ARRL book). Hi John, Perhaps you should offer that definition as its application seems to be quite rare, and paired with some obscurity to the world of sub-atomic dispersion. I looked in some of my dusty old Optics texts to find Brewster: has more to do with polarization. Brewster's angle is the incident angle of light at which the reflected beam is the most completely polarized. My bad. I was thinking of the critical angle above which the light is reflected back from the media interface and below which the light is refracted through the "2nd" medium. PseudoBrewster's Angle (PBA) is the "angle at which the reflected wave is 90 degrees out of phase with respect to the direct wave" (p. 3-13 ARRL Antenna Book). I see now that Both Brewster and PBA have to do with polarization. I guess I was trying to get at how much ham radio is propagated into space. Certainly SOME does. SOME about covers it (you want that specified in dB?). I suppose by your other references to SETI you are wondering about the chances of a QSO in the same frequency from the other side of that ionospheric curtain. Not really looking for a QSO. Just trying to imagine SWL from a different vantage point, I guess. Given the odds, one frequency is as good as the next.... How does this compare to that amount propagated into space by Broadcast? There you have to consider the magnitude of flux, continuously, over the years. If the broadcasting is from Fox news (or any Murdoch source for that matter), it will be indistinguishable from pinko noise. Short entries in some entity's log: "No intelligent life found" and "why am I suddenly hungry?". 73's Richard Clark, KB7QHC |
HFTA-ARRL-Space
Dave wrote:
"Owen Duffy" wrote in message ... On Sat, 01 Jul 2006 16:11:42 -0700, Richard Clark wrote: On the other hand, at HF the ratio between reflection and refraction varies. There are times when both occur. During those times the portion of the incident ray that is reflected returns to earth, while the portion that is refracted continues on through the ionosphere into space and never returns. I'm not sufficiently knowledgeable on the But is it actually reflection? no, it is actually a refraction. but it is useful sometimes to model it as a reflection from a slightly higher level. that makes computation of angles of incidence and height a bit easier. If the end result is that the wave returns back to earth, why is this not termed reflection? Even if it is the result of several and/or continuous refractions that result in a return of the wave from the 2nd medium to the 1st, i.e., they sum to result in a reflected angle, seems to me reflection is a good term. I understand that a curved surface is more complex but if the result is the same, ...? |
HFTA-ARRL-Space
On Thu, 06 Jul 2006 22:42:57 -0400, jawod wrote:
PseudoBrewster's Angle (PBA) is the "angle at which the reflected wave is 90 degrees out of phase with respect to the direct wave" (p. 3-13 ARRL Antenna Book). Hi John, That sounds like ****-poor definition. I see now that Both Brewster and PBA have to do with polarization. And certainly one has very little to do with the other - except for polarization. I'm surprised the author of that article didn't append his own name to the angle. Not really looking for a QSO. Just trying to imagine SWL from a different vantage point, I guess. Somewhere near the 15 meter band you can get the noise field from Jupiter. Not exactly sentient, but still an exotic contact. 73's Richard Clark, KB7QHC |
HFTA-ARRL-Space
"Richard Clark" wrote in message ... Somewhere near the 15 meter band you can get the noise field from Jupiter. Not exactly sentient, but still an exotic contact. 73's Richard Clark, KB7QHC http://www.nasm.si.edu/ceps/etp/jupi.../JUP_radio.gif Jupiter is a broadband radiator. Be glad it stays far away. |
| All times are GMT +1. The time now is 07:44 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com