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#1
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Expeditionradio wrote:
Nothing subjective about it, Cecil. On SSB, I can double my power output by whistling into the microphone. That seems pretty subjective to me. On the 5 MHz thing, since a dipole is almost 100% efficient, does the 50 watt rule mean radiated power? Can I run 500 watts mobile if my mobile antenna is 9% efficient? -- 73, Cecil http://www.qsl.net/w5dxp -----= 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! =----- |
#2
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Cecil Moore wrote:
On the 5 MHz thing, since a dipole is almost 100% efficient, does the 50 watt rule mean radiated power? Can I run 500 watts mobile if my mobile antenna is 9% efficient? That would appear to be the case: http://www.arrl.org/FandES/field/reg...faq.html#three 73 ... WA7AA -- Anti-spam measu look me up on qrz.com if you need to reply directly |
#3
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Zoran Brlecic wrote:
Cecil Moore wrote: On the 5 MHz thing, since a dipole is almost 100% efficient, does the 50 watt rule mean radiated power? Can I run 500 watts mobile if my mobile antenna is 9% efficient? That would appear to be the case: http://www.arrl.org/FandES/field/reg...faq.html#three Has anyone realized that will make a hamstick get out just as well as a bugcatcher? -- 73, Cecil, W5DXP |
#4
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Zoran Brlecic wrote:
http://www.arrl.org/FandES/field/reg...faq.html#three Wow, all sorts of ramifications. A one-wavelength dipole has about 3dB gain over a 1/2WL dipole so one must reduce one's power to 25 watts. OTOH, since a 1/2WL dipole over ground has about 6dB gain over a 1/4WL ground-mounted vertical, can one run 200 watts when using a 1/4WL vertical? -- 73, Cecil, W5DXP |
#5
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Cecil,
I am no expert on the "legalese", but it appears the FCC has specified power in terms of Effective Radiated Power (ERP). The standard is no more than 50-watts radiated by a dipole in free space. My interpretation is that you look at the performance of your antenna at its maximum radiation point (i.e., the azimuth & elevation) and compare it to the radiation from a dipole in free space at its maximum radiation point(s). If your antenna has less radiated power than the dipole, then you can feed more power to the antenna (up to the point that you get the same radiation as a dipole in free space). I think this is the first time the FCC has used ERP (which includes antenna gain and feedline loss) as a power specification for amateur radio. Greg Queen AE6MF "Cecil Moore" wrote in message ... Zoran Brlecic wrote: http://www.arrl.org/FandES/field/reg...faq.html#three Wow, all sorts of ramifications. A one-wavelength dipole has about 3dB gain over a 1/2WL dipole so one must reduce one's power to 25 watts. OTOH, since a 1/2WL dipole over ground has about 6dB gain over a 1/4WL ground-mounted vertical, can one run 200 watts when using a 1/4WL vertical? -- 73, Cecil, W5DXP |
#6
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Hm. That means that you can't run more than about 16-20 watts to an
ordinary dipole, since a dipole over ground produces a field strength that's typically 4-5 dB greater than a dipole in free space. See, for example, the EZNEC example BYDipole.EZ, which shows a field strength of 6.82 dBi, or about 4.7 dB greater than a free space dipole. Roy Lewallen, W7EL Greg Queen wrote: Cecil, I am no expert on the "legalese", but it appears the FCC has specified power in terms of Effective Radiated Power (ERP). The standard is no more than 50-watts radiated by a dipole in free space. My interpretation is that you look at the performance of your antenna at its maximum radiation point (i.e., the azimuth & elevation) and compare it to the radiation from a dipole in free space at its maximum radiation point(s). If your antenna has less radiated power than the dipole, then you can feed more power to the antenna (up to the point that you get the same radiation as a dipole in free space). I think this is the first time the FCC has used ERP (which includes antenna gain and feedline loss) as a power specification for amateur radio. Greg Queen AE6MF |
#7
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From: Roy W7EL wrote
Hm. That means that you can't run more than about 16-20 watts to a n ordinary dipole, since a dipole over ground produces a field strength that's typically 4-5 dB greater than a dipole in free space. Roy, the FCC has clarified this issue recently in communications with ARRL. The FCC indicated we should do all our compliance calculations for 5MHz as if the antennas are in free space. That certainly makes it a lot easier, doesn't it? Bonnie KQ6XA |
#8
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Thanks for the info. It sure does make it easier. Grounded antennas like
a ground mounted vertical or inverted L could be modeled by removing ground and adding a mirror image in free space, or by using perfect ground and subtracting 3 dB from the resulting field. Roy Lewallen, W7EL Expeditionradio wrote: From: Roy W7EL wrote Hm. That means that you can't run more than about 16-20 watts to a n ordinary dipole, since a dipole over ground produces a field strength that's typically 4-5 dB greater than a dipole in free space. Roy, the FCC has clarified this issue recently in communications with ARRL. The FCC indicated we should do all our compliance calculations for 5MHz as if the antennas are in free space. That certainly makes it a lot easier, doesn't it? Bonnie KQ6XA |
#9
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Greg Queen wrote:
I am no expert on the "legalese", but it appears the FCC has specified power in terms of Effective Radiated Power (ERP). The standard is no more than 50-watts radiated by a dipole in free space. My interpretation is that you look at the performance of your antenna at its maximum radiation point (i.e., the azimuth & elevation) and compare it to the radiation from a dipole in free space at its maximum radiation point(s). If your antenna has less radiated power than the dipole, then you can feed more power to the antenna (up to the point that you get the same radiation as a dipole in free space). But a horizontal dipole over ground has a gain over a dipole in free space. Consider a horizontal dipole with a maximum gain of 6 dBi Vs a free space dipole with a maximum gain of 2.14 dBi. Do you have to decrease the power to the horizontal dipole over ground to bring it down to 2.14 dBi? Consider a vertical dipole with a maximum gain of 0 dBi. Can the power be increased to obtain the free space 2.14 dBi or 6 dBi over ground? -- 73, Cecil http://www.qsl.net/w5dxp -----= 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! =----- |
#10
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Greg Queen wrote:
I am no expert on the "legalese", but it appears the FCC has specified power in terms of Effective Radiated Power (ERP). The standard is no more than 50-watts radiated by a dipole in free space. % Bonnie KQ6XA (in a slightly different thread): % Roy, the FCC has clarified this issue recently % in communications with ARRL. The FCC indicated % we should do all our compliance calculations % for 5MHz as if the antennas are in free space. Cecil, W5DXP: Consider a vertical dipole with a maximum gain of 0 dBi. Can the power be increased to obtain the free space 2.14 dBi or 6 dBi over ground? Don't ask. Don't tell. Don't pursue. K7JEB |
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