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#51
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On Sat, 25 Oct 2003 07:09:10 -0500, Neil Down
wrote: wrote in : On Sat, 25 Oct 2003 02:21:12 -0400, wrote: On Fri, 24 Oct 2003 22:23:48 -0700, Frank Gilliland wrote: In , lancer wrote: snip Chrome has about the same conductivity that Stainless does, or at least from the info I found. 3-15% for Stainless, 19% for chrome, relative to copper. For a conductor 102" long with a diameter of 0.625", the following metals have the following AC resistance at 27 MHz: Chromium .0194 ohms Copper .00711 ohms S. Steel .0451 ohms http://www.amm.com/index2.htm?/ref/conduct.HTM Chrome has 55% the conductivity of copper Steel (all types ) 3% - 15% 17-7 ph stainless steel is used for most stainless antennas Its resistivity compared to the standard (copper) can be found here http://www.hpmetals.com/elec_resist.asp Copper = 1.71 microohm-cm 17-7 ph = 83 microohm-cm In other words stainless antenna stock has 2% the conductivity of copper. What type of material is the whip of the exterminator? SS right, the few inches of copper or chrome material of that antenna will make little or no difference what so ever, you guys are nit picking about something that in this application is un noticeable. The top section of that antenna is made from stainless steel. The top section also has very little current flowing in it. The bottom section has a majority of the current flow and does most of the radiation. It maybe nit picking, but in theory the difference can be seen. If you would see it in the real world is another question. |
#52
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On Fri, 24 Oct 2003 15:49:41 -0500, Neil Down
wrote: lancer wrote in : On Thu, 23 Oct 2003 17:23:26 -0500, Neil Down wrote: "(Scott Unit 69)" wrote in : I wish someone who knew what they were talking about would tell the truth about this antenna.There is enough BS on this group as it is without more myths being spread. The funniest part this antenna is made by workman it is junk, the coils are low Q. No way on gods green earth it beats a full 1/4 wave. No, the coils aren't low Q Yes they are compared to a high q coil. What do you consider high Q? Q (Quality factor) is equal to the inductive reactance/the resistance or loss Capacitive coupling between the turns is part of the loss. The coils for that antenna are large diameter tubing, less resistance. They are spaced from eath other by at least a diameter, less capacitive coupling. They are "air wound", less loss due to the coil form. The coils on that antenna have a Q of 100-300 In a typical tank circuit of a transmitter, smaller wire wound closer together on a ceramic form, a Q of 20 is considered very good. You make think that those coils look like they do for show, there is a proven reason why large diameter, large gauge material is used for the coils. And its not just for the power handling capability. |
#53
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In , Frank Gilliland
wrote: In , lancer wrote: snip Chrome has about the same conductivity that Stainless does, or at least from the info I found. 3-15% for Stainless, 19% for chrome, relative to copper. For a conductor 102" long with a diameter of 0.625", the following metals have the following AC resistance at 27 MHz: Chromium .0194 ohms Copper .00711 ohms S. Steel .0451 ohms By golly, I made -another- mistake in my math, which is not such a suprise. But when I was double-checking my work this time I ran across something that everyone should find VERY significant. So from the beginning..... S = Skin depth in meters = sqrt(2/(2*pi*f*u*q)), where q = conductivity of conductor (mhos/m), and u = 4piE07 * relative permeability of medium This is what's interesting. Stainless steel comes in many varieties. Some of them aren't even steel but use the term because they are used for the same applications. Regardless, some stainless steel is ferromagnetic and some is not. The nonferromagnetic steel will have a relative permeability close to that of copper, or 1 for all practical purposes. OTOH, ferromagnetic steel will have a relative permeability much higher, and the value of 500 was used in the calculations below. AC resistance in ohms = l / (q * S * 2 * pi * r), where l = length of conductor (in meters) r = radius of conductor (in meters) Note that there are two different listings for the conductivity of chromium. The first value is based on the information that it is 55% of the conductivity of copper, and the second value (as well as the values for copper and stainless steel) is based upon CRC's HC&P: Cu Cr #1 Cr #2 S.S. S.S. (ferro) Conductivity: 5.80E07 3.19E07 .769E07 .166E07 .166E07 Skin depth: 12.7E-06 17.1E-06 34.9E-06 75.2E-06 3.36E-06 AC resistance: .0705 ohms .0952 ohms .194 ohms .161 ohms 9.31 ohms!!! Notice that the differences in the resistance are all insignificant except for the ferromagnetic stainless steel. This is because of it's high relative permeability. Now when I realized this issue I put a magnet to my whip it doesn't stick. So I went to the shop this morning and checked a number of SS whips of different lengths. Some were magnetic and some were not. The magnetic whips are now all in a pile for other uses. So even old farts like me can learn something new. From now on I'll recommend to everyone to check an antenna with a magnet before buying it, because that's what I intend to do myself. Now, back to the X-terminator. Comparing the difference in radiation efficiency with regards to length and polarization, the 102" whip has 102" that are vertical. Everything is sent vertically polarized. Nothing is wasted in horizontal polarization. OTOH, the X-terminator has 9.5" vertical, followed by 74" of coil, then 3.75" vertical, 41.23" of coil, 5.5" vertical, and 32" of (gasp!) stainless steel. So you have a total of 166" of conductor, with 50.75" of it radiating the desired vertically polarized radiation, but 115" of it dumping horizontal hash. Let's disregard for the moment that 32" (or 63%) of the vertical total is made of that infamous stainless steel, and forget the extra overall resistance due to the additional length of conductor needed to wind the coils. Let's concentrate instead on the fact that the coils consume 69% of the total 'wire' in this antenna. Now if the current distribution was even throughout the length of the antenna, that would mean the coils are radiating 69% of the power as multi-phasic mush. But that's not the case, as the coils are positioned near the base of the antenna, where the antenna's current distribution is the greatest. That means the coils are radiating -more- than if the current was evenly distributed, and therefore -more- than 69%! And that means the efficiency of the X-terminator is less than 31%!!! And if that isn't bad enough, let's take a look at an el-cheapo 102" stainless steel whip of -magnetic- persuasion. If the whip has an AC resistance of 9.31 ohms, and the input impedance is an ideal 50 ohms, that translates into a loss of only 19%. If the input impedance is 36.5 ohms, the wire diameter is 0.25", and accounting for power reflected back to the radio due to mismatch, loss is still well below 30%. Both scenarios are a -hell- of a lot better than the 69% waste caused by the X-terminator's loading coils, and we didn't even go into absorbtion, reflection, hysteresis and eddy current losses caused from the vehicle roof right below those coils!!! So yes, stainless steel -is- more resistive than chromium. But the difference is not significant. So I'll say it again -- there is no way that this antenna will outperform an unloaded 102" whip whether it's made of fiberglass, stainless steel OR ferromagnetic steel! -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#54
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Very nice job Frank............................................. .....
Now, go buy a 7 foot SkipShooter and out talk the 102". Train LOL "Frank Gilliland" wrote in message ... In , Frank Gilliland wrote: In , lancer wrote: snip Chrome has about the same conductivity that Stainless does, or at least from the info I found. 3-15% for Stainless, 19% for chrome, relative to copper. For a conductor 102" long with a diameter of 0.625", the following metals have the following AC resistance at 27 MHz: Chromium .0194 ohms Copper .00711 ohms S. Steel .0451 ohms By golly, I made -another- mistake in my math, which is not such a suprise. But when I was double-checking my work this time I ran across something that everyone should find VERY significant. So from the beginning..... S = Skin depth in meters = sqrt(2/(2*pi*f*u*q)), where q = conductivity of conductor (mhos/m), and u = 4piE07 * relative permeability of medium This is what's interesting. Stainless steel comes in many varieties. Some of them aren't even steel but use the term because they are used for the same applications. Regardless, some stainless steel is ferromagnetic and some is not. The nonferromagnetic steel will have a relative permeability close to that of copper, or 1 for all practical purposes. OTOH, ferromagnetic steel will have a relative permeability much higher, and the value of 500 was used in the calculations below. AC resistance in ohms = l / (q * S * 2 * pi * r), where l = length of conductor (in meters) r = radius of conductor (in meters) Note that there are two different listings for the conductivity of chromium. The first value is based on the information that it is 55% of the conductivity of copper, and the second value (as well as the values for copper and stainless steel) is based upon CRC's HC&P: Cu Cr #1 Cr #2 S.S. S.S. (ferro) Conductivity: 5.80E07 3.19E07 .769E07 .166E07 .166E07 Skin depth: 12.7E-06 17.1E-06 34.9E-06 75.2E-06 3.36E-06 AC resistance: .0705 ohms .0952 ohms .194 ohms .161 ohms 9.31 ohms!!! Notice that the differences in the resistance are all insignificant except for the ferromagnetic stainless steel. This is because of it's high relative permeability. Now when I realized this issue I put a magnet to my whip it doesn't stick. So I went to the shop this morning and checked a number of SS whips of different lengths. Some were magnetic and some were not. The magnetic whips are now all in a pile for other uses. So even old farts like me can learn something new. From now on I'll recommend to everyone to check an antenna with a magnet before buying it, because that's what I intend to do myself. Now, back to the X-terminator. Comparing the difference in radiation efficiency with regards to length and polarization, the 102" whip has 102" that are vertical. Everything is sent vertically polarized. Nothing is wasted in horizontal polarization. OTOH, the X-terminator has 9.5" vertical, followed by 74" of coil, then 3.75" vertical, 41.23" of coil, 5.5" vertical, and 32" of (gasp!) stainless steel. So you have a total of 166" of conductor, with 50.75" of it radiating the desired vertically polarized radiation, but 115" of it dumping horizontal hash. Let's disregard for the moment that 32" (or 63%) of the vertical total is made of that infamous stainless steel, and forget the extra overall resistance due to the additional length of conductor needed to wind the coils. Let's concentrate instead on the fact that the coils consume 69% of the total 'wire' in this antenna. Now if the current distribution was even throughout the length of the antenna, that would mean the coils are radiating 69% of the power as multi-phasic mush. But that's not the case, as the coils are positioned near the base of the antenna, where the antenna's current distribution is the greatest. That means the coils are radiating -more- than if the current was evenly distributed, and therefore -more- than 69%! And that means the efficiency of the X-terminator is less than 31%!!! And if that isn't bad enough, let's take a look at an el-cheapo 102" stainless steel whip of -magnetic- persuasion. If the whip has an AC resistance of 9.31 ohms, and the input impedance is an ideal 50 ohms, that translates into a loss of only 19%. If the input impedance is 36.5 ohms, the wire diameter is 0.25", and accounting for power reflected back to the radio due to mismatch, loss is still well below 30%. Both scenarios are a -hell- of a lot better than the 69% waste caused by the X-terminator's loading coils, and we didn't even go into absorbtion, reflection, hysteresis and eddy current losses caused from the vehicle roof right below those coils!!! So yes, stainless steel -is- more resistive than chromium. But the difference is not significant. So I'll say it again -- there is no way that this antenna will outperform an unloaded 102" whip whether it's made of fiberglass, stainless steel OR ferromagnetic steel! -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#55
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On Sat, 25 Oct 2003 21:33:07 GMT, "Train" wrote:
Very nice job Frank............................................. ..... Now, go buy a 7 foot SkipShooter and out talk the 102". Train LOL Frank really gets into his work. Now if he could just transfer that energy to an actual test. The paper work is interesting but does nothing to show how a 102" SS marginally fails to beat some shorter antennas. Theory and formulas are fine but they will never include all the variables. When the results are to close to call you have to go to the end all. The actual test. |
#56
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#57
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Yup, the same AOL addy that feels rejected because of their ego being
handed to them on daily basis... |
#59
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Steveo wrote:
wrote: On 24 Oct 2003 02:52:14 GMT, Steveo wrote: wrote: Ok Tnom, You've peaked my interest. URL? I think bills two way sells them? Who makes it? Workman? Is this one ok ? $36.95 SP-5000 X-Terminator V, 1000 Watt Single Open air coil, 1/8" square Copper wire, 70 inch overall length. So anyway Tnom, is the above version ok or do have a recommendation? |
#60
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Steveo wrote: Steveo wrote: wrote: On 24 Oct 2003 02:52:14 GMT, Steveo wrote: wrote: Ok Tnom, You've peaked my interest. URL? I think bills two way sells them? Who makes it? Workman? Is this one ok ? $36.95 SP-5000 X-Terminator V, 1000 Watt Single Open air coil, 1/8" square Copper wire, 70 inch overall length. So anyway Tnom, is the above version ok or do have a recommendation? Don't buy it, Steve. |
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