Re: Effective length of half wave dipole
Uh,... By "effective length" do you mean the comparison of the length to a standard dipole? What I mean is, a 1/4 wave dipole against a ground plane is (?)0.95 a dipole and a 1/8 wave dipole TUNED to resonate is (?)0.91 effective length. In other words, for receiving signals a short antenna works as well as a long antenna and has nearly the same effective length. - Robert - Robert A. Macy, PE .. m...@california.com 408 286 3985 . . . .. . . fx 408 297 9121 AJM International Electronics Consultants 101 E San Fernando, Suite 402 San Jose, CA 95112 This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Effective length of half wave dipole
Ken Javor wrote: >> I've seen that design in a D-dot sensor. The elements were a couple of spheres. The output impedance of such an "antenna" is quite high, it really is an electric field probe, and works at frequencies where the elements are electrically short. These types of devices really sense the time derivative of the filed, hence the name. They are fitted with ...<< A dipole of half-spheres on the surface of a single sphere seems popular, perhaps because it is convenient for self-contained devices (inside the sphere) and easy to model. There is at least one - there are probably more -- firm making emissions standards or field sensors using this configuration. The shortening of a dipole can't be attributed solely to the difference between perfect and real materials. Kraus derives the impedance of a half-wave, center fed dipole antenna (Antennas, chapter 10) of negligible thickness and perfect conductivity as 73 + j42.5 ohms. Because this impedance is inductive, resonance requires shortening. However, it has often been noted for real antennas that that the lowest VSWR (50 ohm) does not occur at resonance. Of course we get higher capacitance with a real wire, which adds to the shortening effect, and there's got to be SOME phase shift due to the RC time constant of conductor resistance and capacitance. I don't know that anyone has ever quantified that. Might be an interesting experiment. Cortland This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Effective length of half wave dipole
I've seen that design in a D-dot sensor. The elements were a couple of spheres. The output impedance of such an "antenna" is quite high, it really is an electric field probe, and works at frequencies where the elements are electrically short. These types of devices really sense the time derivative of the filed, hence the name. They are fitted with an integrating amplifier if a representation of the electric field is desired. > From: Mike Hopkins > Reply-To: Mike Hopkins > Date: Wed, 29 Oct 2003 15:27:31 -0500 > To: "'robert Macy'" , kcc...@hkpc.org, > emc-p...@majordomo.ieee.org > Subject: RE: Effective length of half wave dipole > > > I think the length of a 1/2 wave dipole in feet is basically 468/f(MHz) > where the ratio of the length to diameter is very large (wire antennas in > the HF region, for example). Making the diameter of the elements larger does > two things: it reduces the overall length of the antenna and increases the > bandwidth of the dipole. > > Sounds like a new product: and infinately short dipole useable over an > infinately large range of frequencies! The only drawback is the diameter > needs to be infinately large > Oh well, can't have everything > > Best Regards, > > Michael Hopkins > Manager, EMC Technologies > Thermo Electron > Control Technology Division > EMC & ESD Simulation Solutions > One Lowell Research Center > Lowell, MA 01852 > Tel: +1 978 275 0800 ext. 334 > Fax: +1 978 275 0850 > michael.hopk...@thermo.com > www.thermo.com/esd > > One Thermo, committed to integrity, intensity, innovation & involvement > > > -Original Message- > From: robert Macy [mailto:m...@california.com] > Sent: Wednesday, October 29, 2003 1:54 PM > To: kcc...@hkpc.org; emc-p...@majordomo.ieee.org > Subject: Re: Effective length of half wave dipole > > > >> From Dave Cuthbert's comments to me regarding a 1/4 > wavelength dipole; he said that the current moves down the > rod as the rod becomes thicker, which implies that the > current distribution absolutely determines the effective > length. Was that "effective length" or "tuned length"? hmm > > However, the whole thing may start with the conductivity of > real life materials... > > Interesting to see the others' comments. > > - Robert - > > Robert A. Macy, PE .. m...@california.com > 408 286 3985 . . . .. . . fx 408 297 9121 > AJM International Electronics Consultants > 101 E San Fernando, Suite 402 > San Jose, CA 95112 > > > On Wed, 29 Oct 2003 16:59:20 +0800 > kcc...@hkpc.org wrote: >> >> >> Dear all >> >> I got confused with the effective length of a half wave >> dipole. >> >> 1) It is due to non-constant current distribution, or >> >> 2) It is due to the wave velocity in materials different >> from that in >> vacuum. >> >> >> What do you think which one is correct? >> >> Regards >> KC Chan >> > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc >
RE: Effective length of half wave dipole
I think the length of a 1/2 wave dipole in feet is basically 468/f(MHz) where the ratio of the length to diameter is very large (wire antennas in the HF region, for example). Making the diameter of the elements larger does two things: it reduces the overall length of the antenna and increases the bandwidth of the dipole. Sounds like a new product: and infinately short dipole useable over an infinately large range of frequencies! The only drawback is the diameter needs to be infinately large Oh well, can't have everything Best Regards, Michael Hopkins Manager, EMC Technologies Thermo Electron Control Technology Division EMC & ESD Simulation Solutions One Lowell Research Center Lowell, MA 01852 Tel: +1 978 275 0800 ext. 334 Fax: +1 978 275 0850 michael.hopk...@thermo.com www.thermo.com/esd One Thermo, committed to integrity, intensity, innovation & involvement From: robert Macy [mailto:m...@california.com] Sent: Wednesday, October 29, 2003 1:54 PM To: kcc...@hkpc.org; emc-p...@majordomo.ieee.org Subject: Re: Effective length of half wave dipole >From Dave Cuthbert's comments to me regarding a 1/4 wavelength dipole; he said that the current moves down the rod as the rod becomes thicker, which implies that the current distribution absolutely determines the effective length. Was that "effective length" or "tuned length"? hmm However, the whole thing may start with the conductivity of real life materials... Interesting to see the others' comments. - Robert - Robert A. Macy, PE .. m...@california.com 408 286 3985 . . . .. . . fx 408 297 9121 AJM International Electronics Consultants 101 E San Fernando, Suite 402 San Jose, CA 95112 On Wed, 29 Oct 2003 16:59:20 +0800 kcc...@hkpc.org wrote: > > > Dear all > > I got confused with the effective length of a half wave > dipole. > > 1) It is due to non-constant current distribution, or > > 2) It is due to the wave velocity in materials different > from that in > vacuum. > > > What do you think which one is correct? > > Regards > KC Chan > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Effective length of half wave dipole
>From Dave Cuthbert's comments to me regarding a 1/4 wavelength dipole; he said that the current moves down the rod as the rod becomes thicker, which implies that the current distribution absolutely determines the effective length. Was that "effective length" or "tuned length"? hmm However, the whole thing may start with the conductivity of real life materials... Interesting to see the others' comments. - Robert - Robert A. Macy, PE .. m...@california.com 408 286 3985 . . . .. . . fx 408 297 9121 AJM International Electronics Consultants 101 E San Fernando, Suite 402 San Jose, CA 95112 On Wed, 29 Oct 2003 16:59:20 +0800 kcc...@hkpc.org wrote: > > > Dear all > > I got confused with the effective length of a half wave > dipole. > > 1) It is due to non-constant current distribution, or > > 2) It is due to the wave velocity in materials different > from that in > vacuum. > > > What do you think which one is correct? > > Regards > KC Chan > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Effective length of half wave dipole
It is also due to the change in propagation velocity along the antenna as a function of the diameter of the elements. If the elements were of 0 diameter you would be able to totally disregard this factor. Details can be found in the ARRL Handbook. Ghery Pettit Intel Corporation N6TPT From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of kcc...@hkpc.org Sent: Wednesday, October 29, 2003 12:59 AM To: emc-p...@majordomo.ieee.org Subject: Effective length of half wave dipole Dear all I got confused with the effective length of a half wave dipole. 1) It is due to non-constant current distribution, or 2) It is due to the wave velocity in materials different from that in vacuum. What do you think which one is correct? Regards KC Chan This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Effective length of half wave dipole
And also the circumference of the element. And, Yes, wave velocity is certainly different in mediums other than vaccum affected by permeability and permitivity. Engineering Manager BACL 230 Commercial Street Sunnyvale CA 94085 USA 408-732-9162 x38 408-732-9164 fax - Original Message - From: "Luke Turnbull" To: ; Sent: Wednesday, October 29, 2003 2:07 AM Subject: Re: Effective length of half wave dipole > > I assume you are referring to the fact that the length of a practical antenna is about 95% of the theoretical length. > > One significant influence is the end capacitance of a thick dipole, effectively caused by the electric field fringing from the sides of the element round to the end. > > Hope this helps, > > Luke Turnbull > > >>> 10/29/03 08:59am >>> > > > Dear all > > I got confused with the effective length of a half wave dipole. > > 1) It is due to non-constant current distribution, or > > 2) It is due to the wave velocity in materials different from that in > vacuum. > > > What do you think which one is correct? > > Regards > KC Chan > > > > > > > > > > > > > > > > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Effective length of half wave dipole
I assume you are referring to the fact that the length of a practical antenna is about 95% of the theoretical length. One significant influence is the end capacitance of a thick dipole, effectively caused by the electric field fringing from the sides of the element round to the end. Hope this helps, Luke Turnbull >>> 10/29/03 08:59am >>> Dear all I got confused with the effective length of a half wave dipole. 1) It is due to non-constant current distribution, or 2) It is due to the wave velocity in materials different from that in vacuum. What do you think which one is correct? Regards KC Chan This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Effective length of half wave dipole
Dear all I got confused with the effective length of a half wave dipole. 1) It is due to non-constant current distribution, or 2) It is due to the wave velocity in materials different from that in vacuum. What do you think which one is correct? Regards KC Chan This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
