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Who has an ideal horizontal dipole for HF?
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Hash: SHA1 So who actually has the space and resources to set up an ideal horizontal dipole on HF with the full length and height as specified in all the formulas? Wouldn't it be cheaper and easier to set up a vertical if you could install something that high off the ground? The only thing I've seen personally that looks like it meets the ideal is a small station tucked into the northeast cloverleaf of an exit off Interstate 93 near Boston, MA, and the station appeared to be a marker for Logan. Anyone have any personal, real-life experience with a full-size, full-height HF dipole? Is it worth the cost? Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFApPwtGPFSfAB/ezgRAnsaAKCknbXs5lF7jihTaR8Xv6ENgxViBwCgyjhH TfOqae1e0YBHG3B9ldy4mhg= =hAum -----END PGP SIGNATURE----- |
On Fri, 14 May 2004 10:04:38 -0700, Jack Twilley
wrote: Anyone have any personal, real-life experience with a full-size, full-height HF dipole? Is it worth the cost? Hi Jack, There is no such thing. Full size and Full height for a band that has a frequencies spanning 15:1 is a contradiction. One antenna must be either significantly fuller sized or fuller heighted at some frequency, or suffer at another frequency as lesser sized or lesser heighted for the same reason. You want a 10M dipole antenna up half a wave for 160M? Is half a wave full height? Is a 10M dipole full sized? Describe your needs first, and then ask what would be reasonable. 73's Richard Clark, KB7QHC |
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Hash: SHA1 "Richard" == Richard Clark writes: Jack Anyone have any personal, real-life experience with a full-size, Jack full-height HF dipole? Is it worth the cost? Richard Hi Jack, Richard There is no such thing. Full size and Full height for a band Richard that has a frequencies spanning 15:1 is a contradiction. One Richard antenna must be either significantly fuller sized or fuller Richard heighted at some frequency, or suffer at another frequency as Richard lesser sized or lesser heighted for the same reason. I regret that my message was insufficiently specific. I didn't say "all-bands HF", and I assumed that the potential respondents would know that I knew that no single dipole is ideal for more than one band (well, more than one *frequency*, but one band is close enough). Richard You want a 10M dipole antenna up half a wave for 160M? Is Richard half a wave full height? Is a 10M dipole full sized? I am interested in people who have first-hand experience with a full-length dipole mounted at the full height for any particular band. A 10M dipole is full-sized if it's the full length and mounted at the full height. Ditto for 160M. Richard Describe your needs first, and then ask what would be Richard reasonable. I hope the clarification above is enough -- if not, please let me know. Richard 73's Richard Clark, KB7QHC Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFApSuMGPFSfAB/ezgRAiYvAJ0Z5rUplnVMvIs2ZpVP5Ska6Rv3JgCfXXZb Y+8B1+VqlzeNkgXyQdwtBpQ= =YpAB -----END PGP SIGNATURE----- |
On Fri, 14 May 2004 13:26:45 -0700, Jack Twilley
wrote: I am interested in people who have first-hand experience with a full-length dipole mounted at the full height for any particular band. A 10M dipole is full-sized if it's the full length and mounted at the full height. Ditto for 160M. Richard Describe your needs first, and then ask what would be Richard reasonable. I hope the clarification above is enough -- if not, please let me know. Hi Jack, This is still inspecific. "Full height" is actually meaningless. Let's look at a 40M dipole antenna and choose a modest 20° launch angle to compare against. 5M over real ground: -2dBi 10M over real ground: 1.29dBi 15M over real ground: 3.75dBi 20M over real ground: 6.27dBi 25M over real ground: 8.08dBi 30M over real ground: 7.67dBi 35M over real ground: 7.1dBi 40M over real ground: 7.52dBi Well, let's see - best gain is NOT at any cardinal point such as quarter wave, half wave, three quarter, nor full wave above ground ANY of which "could" be interpreted as "full height." This exercise is easily within the limited feature set of the free distribution of EZNEC. 73's Richard Clark, KB7QHC |
Jack Twilley wrote:
So who actually has the space and resources to set up an ideal horizontal dipole on HF with the full length and height as specified in all the formulas? Wouldn't it be cheaper and easier to set up a vertical if you could install something that high off the ground? The only thing I've seen personally that looks like it meets the ideal is a small station tucked into the northeast cloverleaf of an exit off Interstate 93 near Boston, MA, and the station appeared to be a marker for Logan. Anyone have any personal, real-life experience with a full-size, full-height HF dipole? Is it worth the cost? Jack. - -- Interesting question. I have seen the dipoles used for HF communications with transatlantic air traffic from Gander, or at least one site which IIRC was the receiver site. Since this, and similar installations around the world, need reliable communications at a number of frequencies to provide coverage over a wide area and while they may have a kilowatt or so for transmit; on receive they are working with a station whose transmitter is unlikely to exceed 400W PEP and whose antenna is at best a poor compromise since the days of aircraft wire antennas are long gone. I don't know about other sites, but Gander certainly used to have a number of just plain old dipoles; and I have seen other simple dipoles at several other airports and airline installations so one would expect a fair amount of operational data to have been gathered over the years. It seems to me that most of the professional vertical installations I have seen are those which tend to require operation at multiple frequencies with a single antenna - i.e. shipboard and military installations, although there used to be quite a lot of verticals at Coast Guard stations for the 2 MHz band. Re. the installation at Logan; I would be inclined to believe that what you are seeing is a top loaded "T" configuration for a Low Frequency (200 - 400kHz) Non-Directional-Beacon. Dave |
"Jack Twilley" wrote in message ... -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 "Richard" == Richard Clark writes: Jack Anyone have any personal, real-life experience with a full-size, Jack full-height HF dipole? Is it worth the cost? Richard Hi Jack, Richard There is no such thing. Full size and Full height for a band Richard that has a frequencies spanning 15:1 is a contradiction. One Richard antenna must be either significantly fuller sized or fuller Richard heighted at some frequency, or suffer at another frequency as Richard lesser sized or lesser heighted for the same reason. I regret that my message was insufficiently specific. I didn't say "all-bands HF", and I assumed that the potential respondents would know that I knew that no single dipole is ideal for more than one band (well, more than one *frequency*, but one band is close enough). Richard You want a 10M dipole antenna up half a wave for 160M? Is Richard half a wave full height? Is a 10M dipole full sized? I am interested in people who have first-hand experience with a full-length dipole mounted at the full height for any particular band. A 10M dipole is full-sized if it's the full length and mounted at the full height. Ditto for 160M. Richard Describe your needs first, and then ask what would be Richard reasonable. I hope the clarification above is enough -- if not, please let me know. Richard 73's Richard Clark, KB7QHC Jack. ----- Jack, Leaving out the question of "full height", I found that a 20m dipole at 55 feet was outperforming a Junior tribander at 40 feet for distances beyond 2000 miles. Broadside to the dipole, of course. Tam/WB2TT |
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Hash: SHA1 "Richard" =3D=3D Richard Clark writes: Jack I am interested in people who have first-hand experience with a Jack full-length dipole mounted at the full height for any particular Jack band. A 10M dipole is full-sized if it's the full length and Jack mounted at the full height. Ditto for 160M. Richard Describe your needs first, and then ask what would be Richard reasonable. Jack I hope the clarification above is enough -- if not, please let Jack me know. Richard Hi Jack, Richard This is still inspecific. "Full height" is actually Richard meaningless. Let's look at a 40M dipole antenna and choose a Richard modest 20=B0 launch angle to compare against. 5M over real Richard ground: -2dBi 10M over real ground: 1.29dBi 15M over real Richard ground: 3.75dBi 20M over real ground: 6.27dBi 25M over real Richard ground: 8.08dBi 30M over real ground: 7.67dBi 35M over real Richard ground: 7.1dBi 40M over real ground: 7.52dBi Where did the twenty-degree launch angle come from? Richard Well, let's see - best gain is NOT at any cardinal point such Richard as quarter wave, half wave, three quarter, nor full wave Richard above ground ANY of which "could" be interpreted as "full Richard height." I'm not familiar with twenty-degrees as any particular canonical value. As for what I meant by "full height", one-quarter wavelength minimum should serve. Richard This exercise is easily within the limited feature set of the Richard free distribution of EZNEC. I do not doubt that your calculations are within the capabilities of EZNEC. However, I'm more interested in real-life experience, not computer-generated simulations. Richard 73's Richard Clark, KB7QHC Jack. =2D --=20 Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash =2D----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFApZ/cGPFSfAB/ezgRAparAKDulUdO0dGqcrNrCxjkuBZPl203vQCgosND +PUWZk0Lx5NTUyy7Av1quhY=3D =3DksOs =2D----END PGP SIGNATURE----- |
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Hash: SHA1 "Tarmo" == Tarmo Tammaru t-tammaru@c0mca writes: [...] Tarmo Leaving out the question of "full height", I found that a 20m Tarmo dipole at 55 feet was outperforming a Junior tribander at 40 Tarmo feet for distances beyond 2000 miles. Broadside to the dipole, Tarmo of course. This is the kind of experience I had hoped to hear. Thank you. Tarmo Tam/WB2TT Jack. - -- Jack Twilley jmt at twilley dot org http colon slash slash www dot twilley dot org slash tilde jmt slash -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFApaOpGPFSfAB/ezgRAh+DAJ9x8hdoBNgkjtJP4QvnwzbToGd80gCgtPoU 1EcHdxvMWOpRzaWu2A3Dr8U= =sCdx -----END PGP SIGNATURE----- |
On Fri, 14 May 2004 21:43:03 -0700, Jack Twilley
wrote: I'm not familiar with twenty-degrees as any particular canonical value. As for what I meant by "full height", one-quarter wavelength minimum should serve. Richard This exercise is easily within the limited feature set of the Richard free distribution of EZNEC. I do not doubt that your calculations are within the capabilities of EZNEC. However, I'm more interested in real-life experience, not computer-generated simulations. Hi Jack, 20° serves as well as any and at least offers a basis of comparison. This again turns to the matter of the inspecific. You cite no particular application (DX v. NVIS) no particular band (that is heavily swayed by ground given ground characteristics vary over frequency) and offer a quarter wave height as "full height" which by most standards is generally accepted as mediocre at best where half wave height (twice full height?) offers better performance (which is borne out in testimonial) and where higher sometimes offers worse performance (also borne out in testimonial). Such issues are easily isolated and compared through modeling and are consistent with experience. 73's Richard Clark, KB7QHC |
On Fri, 14 May 2004 20:44:40 -0400, Dave Holford
wrote: Interesting question. I have seen the dipoles used for HF communications with transatlantic air traffic from Gander, or at least one site which IIRC was the receiver site. Since this, and similar installations around the world, need reliable communications at a number of frequencies to provide coverage over a wide area and while they may have a kilowatt or so for transmit; on receive they are working with a station whose transmitter is unlikely to exceed 400W PEP and whose antenna is at best a poor compromise since the days of aircraft wire antennas are long gone. I don't know about other sites, but Gander certainly used to have a number of just plain old dipoles; and I have seen other simple dipoles at several other airports and airline installations so one would expect a fair amount of operational data to have been gathered over the years. I worked at a station in Alaska that had a big antenna farm. The station was designed to communicate with aircraft over distances from zero to thousands of miles. We had very few limitations over what we could do or build with unlimited space, and had two rhombic's for communicating with two flights that took the same track every day. Communication was mostly CW five letter group encryption. The transmitters and receivers were separated by 20 miles or so. The operators could choose which transmitter/antenna combination gave them the best performance. The dipoles seemed to be the preferred antenna. The rhombic's (the king of HF antennas) were seldom used, probably because of the radiation pattern. The antenna is the most unpredictable part of any installation. I was the guy that tried to neutralize the big triodes, so you know that was a while ago. (1950's). The globe was about the size of a volleyball. Ron, W1WBV |
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