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#1
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OK, let's discuss dipoles vs length
John S wrote:
snip OK, so lets analyze my results: Conditions are free space, wire is #14 gauge but may have zero ohms where noted. The antenna is a dipole with the source connected at the center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna resonance plays no part in this. # segments = 99 unless otherwise noted. Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency 0.5 zero 80 0 2.16 100% 0.5 #14 73.6 -.09 2.08 98% 0.25 zero 13.2 0 1.85 100% 0.25 #14 13.7 -.17 1.69 96% 0.125 zero 3 0 1.78 100% 0.125 #14 3.25 -.33 1.45 93% 0.05 zero .464 0 1.76 100% 0.05 #14 .556 -.78 0.98 83% Rin is the terminal resistance only. Gave is the average gain integrated over the pattern, Gmax is the highest gain detected. Unless I have done something wrong, I see that a dipole that is .05 wavelengths long is within 20% of being as efficient as a half-wave dipole. Even including wire resistance. I invite discussion in any case. The diameter of #14 solid wire is 0.0641"; how about a line for #8, which is 0.1285"? -- Jim Pennino |
#2
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OK, let's discuss dipoles vs length
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#4
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OK, let's discuss dipoles vs length
On 10/12/2014 1:21 PM, wrote:
John S wrote: On 10/11/2014 12:51 PM, wrote: John S wrote: snip OK, so lets analyze my results: Conditions are free space, wire is #14 gauge but may have zero ohms where noted. The antenna is a dipole with the source connected at the center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna resonance plays no part in this. # segments = 99 unless otherwise noted. Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency 0.5 zero 80 0 2.16 100% 0.5 #14 73.6 -.09 2.08 98% 0.25 zero 13.2 0 1.85 100% 0.25 #14 13.7 -.17 1.69 96% 0.125 zero 3 0 1.78 100% 0.125 #14 3.25 -.33 1.45 93% 0.05 zero .464 0 1.76 100% 0.05 #14 .556 -.78 0.98 83% Rin is the terminal resistance only. Gave is the average gain integrated over the pattern, Gmax is the highest gain detected. Unless I have done something wrong, I see that a dipole that is .05 wavelengths long is within 20% of being as efficient as a half-wave dipole. Even including wire resistance. I invite discussion in any case. The diameter of #14 solid wire is 0.0641"; how about a line for #8, which is 0.1285"? 0.05 #8 0.515 -.41 1.36 91.1% Free space, no ground loss. So it seems that a .05 lamda dipole is only about 7% less efficient than a full size dipole wit suitable wire... So much for "short antennas are not efficient". (snip extraneous input) Yes, Jim, that is so. In fact, that was the hidden reason for the exercise. I was hoping this would provide an example to let others know that it is not the antenna length that is the problem as Gareth proposed. I was hoping that others would take the investigation into their own hands as a result. I noted that you tried to foul me up with the unreasonable wire size. EZNEC has a nice warning feature to take care of it. |
#5
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OK, let's discuss dipoles vs length
John S wrote:
On 10/12/2014 1:21 PM, wrote: John S wrote: On 10/11/2014 12:51 PM, wrote: John S wrote: snip OK, so lets analyze my results: Conditions are free space, wire is #14 gauge but may have zero ohms where noted. The antenna is a dipole with the source connected at the center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna resonance plays no part in this. # segments = 99 unless otherwise noted. Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency 0.5 zero 80 0 2.16 100% 0.5 #14 73.6 -.09 2.08 98% 0.25 zero 13.2 0 1.85 100% 0.25 #14 13.7 -.17 1.69 96% 0.125 zero 3 0 1.78 100% 0.125 #14 3.25 -.33 1.45 93% 0.05 zero .464 0 1.76 100% 0.05 #14 .556 -.78 0.98 83% Rin is the terminal resistance only. Gave is the average gain integrated over the pattern, Gmax is the highest gain detected. Unless I have done something wrong, I see that a dipole that is .05 wavelengths long is within 20% of being as efficient as a half-wave dipole. Even including wire resistance. I invite discussion in any case. The diameter of #14 solid wire is 0.0641"; how about a line for #8, which is 0.1285"? 0.05 #8 0.515 -.41 1.36 91.1% Free space, no ground loss. So it seems that a .05 lamda dipole is only about 7% less efficient than a full size dipole wit suitable wire... So much for "short antennas are not efficient". (snip extraneous input) Yes, Jim, that is so. In fact, that was the hidden reason for the exercise. I was hoping this would provide an example to let others know that it is not the antenna length that is the problem as Gareth proposed. I was hoping that others would take the investigation into their own hands as a result. I noted that you tried to foul me up with the unreasonable wire size. EZNEC has a nice warning feature to take care of it. What "unreasonable wire size"? #8 wire is readily available and often used to make antenna elements, as is 1/8 th aluminum, which is only a few thousands of an inch different. Or are you refering to issues with segmentation and fat, short wires which I thought I had warned you about? -- Jim Pennino |
#6
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OK, let's discuss dipoles vs length
On 10/12/2014 2:14 PM, wrote:
John S wrote: On 10/12/2014 1:21 PM, wrote: John S wrote: On 10/11/2014 12:51 PM, wrote: John S wrote: snip OK, so lets analyze my results: Conditions are free space, wire is #14 gauge but may have zero ohms where noted. The antenna is a dipole with the source connected at the center, F=7MHz. I'm using EZNEC with a source of 1 watt. Antenna resonance plays no part in this. # segments = 99 unless otherwise noted. Lambda Wire Rin Gavg(dbi) Gmax(dbi) Efficiency 0.5 zero 80 0 2.16 100% 0.5 #14 73.6 -.09 2.08 98% 0.25 zero 13.2 0 1.85 100% 0.25 #14 13.7 -.17 1.69 96% 0.125 zero 3 0 1.78 100% 0.125 #14 3.25 -.33 1.45 93% 0.05 zero .464 0 1.76 100% 0.05 #14 .556 -.78 0.98 83% Rin is the terminal resistance only. Gave is the average gain integrated over the pattern, Gmax is the highest gain detected. Unless I have done something wrong, I see that a dipole that is .05 wavelengths long is within 20% of being as efficient as a half-wave dipole. Even including wire resistance. I invite discussion in any case. The diameter of #14 solid wire is 0.0641"; how about a line for #8, which is 0.1285"? 0.05 #8 0.515 -.41 1.36 91.1% Free space, no ground loss. So it seems that a .05 lamda dipole is only about 7% less efficient than a full size dipole wit suitable wire... So much for "short antennas are not efficient". (snip extraneous input) Yes, Jim, that is so. In fact, that was the hidden reason for the exercise. I was hoping this would provide an example to let others know that it is not the antenna length that is the problem as Gareth proposed. I was hoping that others would take the investigation into their own hands as a result. I noted that you tried to foul me up with the unreasonable wire size. EZNEC has a nice warning feature to take care of it. What "unreasonable wire size"? #8 wire is readily available and often used to make antenna elements, as is 1/8 th aluminum, which is only a few thousands of an inch different. Or are you refering to issues with segmentation and fat, short wires which I thought I had warned you about? Ok, wrong choice of words on my part. Sorry. Yes, I kinda thought you were really testing me to see if I paid attention about the warning. |
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