|
Quarterwave vertical with radials
Richard Clark wrote:
On Mon, 10 Jul 2006 17:57:42 -0400, John Popelish wrote: I meant that half as many photons are produced, compared to the full dipole antenna that produces the same fields above the center line. Hi John, So, proceeding along your avowed lines of Photons, one of several questions: Presuming 100W radiated, how many photons would that be so that we can talk about them by halves. Well, you couldn't be radiating 100 watts in both cases if the field strength is the same above the center line, but half the field is missing in one of the cases. But regardless of the radiating structure, if 100 watts at 40 M is being radiated, you are launching about 2*10^28 photons per second. Yes, that is perhaps unfair, however it demonstrates how easily the discussion can tumble for lack of quantifiables such as that original offering of 100W. Hence the stipulation that the field strength above the centerline being constant, rather than the radiated power. I missed that we were only talking about a case of radiating 100 watts. Should we discuss how infinitesimal the energy is in a 40M photon? (Easily accounts for why so many are needed for that same 100W.) Not much to discuss. I don't do such calculations often, but I get about 5*10^-27 joule per photon. What do you calculate their energy to be? No, I suppose not. Do you have some point? Want to get into the problems of diffraction with object lenses that measure less than a wavelength of the photon? Sure. That will take us back to how an elevated radial system gives a different vertical pattern than an actual ground plane or a lossy ground does. You go first. Hard to escape, and makes a mess of describing mirrors too, especially when they are skeletal approximations as well. You have to start understanding mirrors, somewhere. Perhaps you prefer a different starting point. There are several. I can offer more thread-busters when it comes to photonics, but that is a slam dunk. Get us rolling on one ace proposition, and I will get back to you in a couple of hours. I have no idea what you are saying with these two sentences. |
Quarterwave vertical with radials
|
Quarterwave vertical with radials
Richard Clark wrote:
On Mon, 10 Jul 2006 17:57:42 -0400, John Popelish wrote: I meant that half as many photons are produced, compared to the full dipole antenna that produces the same fields above the center line. Hi John, So, proceeding along your avowed lines of Photons, one of several questions: Presuming 100W radiated, how many photons would that be so that we can talk about them by halves. Yes, that is perhaps unfair, however it demonstrates how easily the discussion can tumble for lack of quantifiables such as that original offering of 100W. Should we discuss how infinitesimal the energy is in a 40M photon? (Easily accounts for why so many are needed for that same 100W.) No, I suppose not. Want to get into the problems of diffraction with object lenses that measure less than a wavelength of the photon? Hard to escape, and makes a mess of describing mirrors too, especially when they are skeletal approximations as well. I can offer more thread-busters when it comes to photonics, but that is a slam dunk. Get us rolling on one ace proposition, and I will get back to you in a couple of hours. 73's Richard Clark, KB7QHC How many photons does it take to make a Watt? 73, Tom Donaly, KA6RUH |
Quarterwave vertical with radials
Tom Donaly wrote:
How many photons does it take to make a Watt? 1/(Hz*6.63*10^-34). The lower the frequency the less energy per photon. |
Quarterwave vertical with radials
|
Quarterwave vertical with radials
Reg Edwards wrote:
A pair of radials behave as a continuous dipole fed at its center via a single wire. And it radiates. If the radials are horizontal and radiating, why is there virtually no horizontally polarized radiation? -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
John Popelish wrote:
Remember, it is Cecil, not me, who demands agreement or eternal verbal torture. I don't demand agreement, John, just resolution. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Tom Donaly wrote:
wrote: Cecil Moore wrote: It's pretty easy to understand. Any two radials, 180 degrees apart and high enough, should theoretically cancel each other's radiation in the far field. Not true. How much not true? -45 DB, i.e. negligibly not true. :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Cecil Moore wrote: Funny, I don't see "fully cancel" anywhere in my posting. I probably should have said "tend to cancel". A free space vertical with horizontal radials in EZNEC has horizontal radiation more than 40 dB down from the vertical radiation. That's a high degree of cancellation. The issue is the horizontal opposing radials only have that degree of cancellation for perfectly horizontal directions. You will be able to see your statement isn't true if you place the antenna in freespace and look at pattern distortion at various elevation angles. For example, the 2-d plot is skewed 2.11 dB from being circular at - 45 and +45 degrees elevation. The skewing gets worse at larger angles from the plane of the radials. If the radials were REALLY radiating -40dB in all directions as you wrongly assume, there would NOT be significant FS change in the azimuth pattern at various elevations. You looked at horizontal radiation, but the horizontal radials peak radiation is vertically polarized and nearly off the radial's ends. (Just like in a dipole pattern.) The radials do indeed radiate enough to change the pattern a significant amount (but not at zero degrees), but the largest problem is decoupling the feedline shield. The fewer radials are used, the bigger the problem becomes. There are VERY good reasons everyone settled on four radials, and it isn't the old wive's tale about making the antenna look good. Four radials is a reasonable compromise between excessive common mode problems and tolerable common mode feedline current problems, pattern, and cost. Don't feel bad though Cecil. Many people miss this point, even card carrying Mensa members. 73 Tom |
| All times are GMT +1. The time now is 04:50 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com