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Helical wound slim jim?
Anyone ever done a helical wound "Slim Jim?" Since this is a 1/2 wave
antenna with a 1/4 matching section (3/4 overall), helical winding of this form into a 3/8 overall height (approx. 12 ft. @ 28Mhz) might be possible. The extremely low angle of radiation (approx. 8 degrees) would make this vertical antenna desirable... Regards |
On Sat, 26 Mar 2005 08:18:39 -0800, "John Smith"
wrote: The extremely low angle of radiation Hi John, Rote learning comes through repetition: The physical size in relation to wavelength dominates launch characteristics, NOT electrical length. As slim jims are generally applied to UHF/VHF use, line of sight dominates both - that is why helically wound resistors (HT rubber duckies) work as well as they do. 73's Richard Clark, KB7QHC |
On Sat, 26 Mar 2005 13:37:12 -0800, "John Smith"
wrote: The rubber duckie antenna is certainly useful for some situations, however, it is better if it stays on the walkie-talkie and we use another design for portable or base use. Hi John, Given this opprobrium, what makes its cousin for 20M more suitable? [20M is not noted for being line-of-sight either.] The principle annoyance to erecting antennas is in matching them, beyond that, any radiator from 0.1 to 0.625 wavelengths pretty much has the same gain in the same direction. The difference being that some are harder to interface to a transmitter than others. 73's Richard Clark, KB7QHC |
Hey, have you ever built any antennas? I know it is tempting to go buy a
standard issue one and ask everyone else why they bother, sometimes, I am even tempted myself... Regards "Richard Clark" wrote in message ... On Sat, 26 Mar 2005 13:37:12 -0800, "John Smith" wrote: The rubber duckie antenna is certainly useful for some situations, however, it is better if it stays on the walkie-talkie and we use another design for portable or base use. Hi John, Given this opprobrium, what makes its cousin for 20M more suitable? [20M is not noted for being line-of-sight either.] The principle annoyance to erecting antennas is in matching them, beyond that, any radiator from 0.1 to 0.625 wavelengths pretty much has the same gain in the same direction. The difference being that some are harder to interface to a transmitter than others. 73's Richard Clark, KB7QHC |
On Sat, 26 Mar 2005 17:43:53 -0800, "John Smith"
wrote: Hey, have you ever built any antennas? Hi John, Hoist your own petard, bucko. I display my call, I am among my peers and do not post anonymously (not that your veil hasn't been penetrated Brett). Now, the question again: Given this opprobrium, what makes its cousin for 20M more suitable? 73's Richard Clark, KB7QHC |
Rather, back to my original question (your ADD--attention defecit disorder
is showing), "Anyone ever done a helical wound "Slim Jim?"" Regards "Richard Clark" wrote in message ... On Sat, 26 Mar 2005 17:43:53 -0800, "John Smith" wrote: Hey, have you ever built any antennas? Hi John, Hoist your own petard, bucko. I display my call, I am among my peers and do not post anonymously (not that your veil hasn't been penetrated Brett). Now, the question again: Given this opprobrium, what makes its cousin for 20M more suitable? 73's Richard Clark, KB7QHC |
On Sat, 26 Mar 2005 18:00:30 -0800, "John Smith"
wrote: Rather, back to my original question (your ADD--attention defecit disorder is showing), "Anyone ever done a helical wound "Slim Jim?"" Hi "Jack," I suppose it has to be said if this is going anywhe Yes. Is this 20 questions, or do you have any answers for yourself? 73's Richard Clark, KB7QHC |
"Richard Clark" wrote:
... any radiator from 0.1 to 0.625 wavelengths pretty much has the same gain in the same direction. ________________ This will be news to the FCC and AM broadcast stations, all of whom understand that the ground wave from radiators of the heights you mention above varies WIDELY, as demonstrated by empirical measurements going back some 70 years. For example, a 0.1 lambda radiator has about 54% of the groundwave field as one of 0.625 wavelength, assuming a very good ground system for each (1 ohm or so). A matched radiator of 0.1 lambda height would need about 3-1/2X as much input power as a 0.625 lambda matched radiator in order to generate the same ground wave field strength over the same radio path. RF |
On Sun, 27 Mar 2005 15:29:59 -0600, "Richard Fry"
wrote: This will be news to the FCC and AM broadcast stations Hi OM, Send them a singing telegram. 73's Richard Clark, KB7QHC |
.....Anyone ever done a helical wound "Slim Jim?"
yes. Since this is a 1/2 wave antenna with a 1/4 matching section (3/4 overall), Why the 1/4 matching section? Seems that takes it nearly to the full half wave length...or close enough not to matter much... Myself, I would probably prefer a "gamma loop" type matching scheme, which adds no height. To me, 16 ft tall is no more trouble than 12 ft tall in the real world. I've had a lightweight 32 ft self supporting radiator up, which was no hassle at all...And the base of that was at 36 ft on a mast. "68 ft tall total". That was a dual band 40m GP/ 17m 5/8 GP....Full size on both bands, relay switched. helical winding of this form into a 3/8 overall height (approx. 12 ft. @ 28Mhz) might be possible. The extremely low angle of radiation (approx. 8 degrees) would make this vertical antenna desirable... ...................... The angle of maximum radiation will vary fairly drastically depending on height above ground. For a "like" sized vertical, the height above ground will have more of an effect, than any extra electrical length. To my way of thinking, the advantage of the extended winding should be the largest, the closer to ground it is. The higher above ground, approaching 1/2 wave up, the lesser the advantage. Note that at high heights above ground in WL, the 1/4 wave ground plane, and the 1/2 wave vertical have nearly the same gain for practical purposes. "maybe .3 -.8 db difference..." You should consider decoupling of the antenna from the feedline also. Radiation from the line will skew the pattern upwards off the horizon. This will ruin even higher gain collinears. I like my antennas full size if at all possible. I'm a radio bully. :/ MK |
"Richard Clark" wrote
This will be news to the FCC and AM broadcast stations Hi OM, Send them a singing telegram. _______________ I'll leave that to you, as the author of the news. |
wrote:
Since this is a 1/2 wave antenna with a 1/4 matching section (3/4 overall), Why the 1/4 matching section? An 1/2WL end-fed with 1/4WL matching section is a Zepp. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
To put everyone "on the same page", here is a good description of what I
intend when I mention "slim jim." http://www.hamuniverse.com/slimjim.html Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw aboot speel-checkin it fer me? wrote in message ups.com... ....Anyone ever done a helical wound "Slim Jim?" yes. Since this is a 1/2 wave antenna with a 1/4 matching section (3/4 overall), Why the 1/4 matching section? Seems that takes it nearly to the full half wave length...or close enough not to matter much... Myself, I would probably prefer a "gamma loop" type matching scheme, which adds no height. To me, 16 ft tall is no more trouble than 12 ft tall in the real world. I've had a lightweight 32 ft self supporting radiator up, which was no hassle at all...And the base of that was at 36 ft on a mast. "68 ft tall total". That was a dual band 40m GP/ 17m 5/8 GP....Full size on both bands, relay switched. helical winding of this form into a 3/8 overall height (approx. 12 ft. @ 28Mhz) might be possible. The extremely low angle of radiation (approx. 8 degrees) would make this vertical antenna desirable... ...................... The angle of maximum radiation will vary fairly drastically depending on height above ground. For a "like" sized vertical, the height above ground will have more of an effect, than any extra electrical length. To my way of thinking, the advantage of the extended winding should be the largest, the closer to ground it is. The higher above ground, approaching 1/2 wave up, the lesser the advantage. Note that at high heights above ground in WL, the 1/4 wave ground plane, and the 1/2 wave vertical have nearly the same gain for practical purposes. "maybe .3 -.8 db difference..." You should consider decoupling of the antenna from the feedline also. Radiation from the line will skew the pattern upwards off the horizon. This will ruin even higher gain collinears. I like my antennas full size if at all possible. I'm a radio bully. :/ MK |
On Mon, 28 Mar 2005 06:22:05 -0600, "Richard Fry"
wrote: "Richard Clark" wrote This will be news to the FCC and AM broadcast stations Hi OM, Send them a singing telegram. _______________ I'll leave that to you, as the author of the news. Not as important as you first thought I see - which was my point. 73's Richard Clark, KB7QHC |
"Richard Clark" wrote wrote:
"Richard Clark" wrote This will be news to the FCC and AM broadcast stations Hi OM, Send them a singing telegram. I'll leave that to you, as the author of the news. Not as important as you first thought I see - which was my point. __________________ Readers will judge for themselves as to the importance and validity of our respective statements on this topic. You chose to avoid commenting about the accuracy of what I posted, replying instead with a flip comment. I suspect you know that what I posted was valid -- even though counter to your point of view. RF |
On Mon, 28 Mar 2005 12:17:59 -0600, "Richard Fry"
wrote: I suspect you know that what I posted was valid -- even though counter to your point of view. Knowing Pi out to seventeen places neither validates nor refutes the shape of a pie. The evidence of correspondence proves my point: it doesn't really matter given the greater bulk of your responses lie outside of technical offerings - such data rich marginalia still fails to elevate its pretenses above a trivial concern. 73's Richard Clark, KB7QHC |
....Anyone ever done a helical wound "Slim Jim?"
yes. Since this is a 1/2 wave antenna with a 1/4 matching section (3/4 overall), Why the 1/4 matching section? Seems that takes it nearly to the full half wave length...or close enough not to matter much... Myself, I would probably prefer a "gamma loop" type matching scheme, which adds no height. To me, 16 ft tall is no more trouble than 12 ft tall in the real world. SNIP The SlimJim resembles the J-Pole. The 1/4 wave section is a matching network and it is probably not critical that it be vertical so the height may be reduced by about 1/3. I am not sure what the folded section does for it. but without the 1/2 wave section coming back down from the top, the antenna is just a J-Pole. helical winding of this form into a 3/8 overall height (approx. 12 ft. @ 28Mhz) might be possible. The extremely low angle of radiation (approx. 8 degrees) would make this vertical antenna desirable... ...................... I like my antennas full size if at all possible. I'm a radio bully. :/ MK I am with you here, when it is possible and practical. -- 73 for now Buck N4PGW |
In article ,
Buck wrote: The SlimJim resembles the J-Pole. The 1/4 wave section is a matching network and it is probably not critical that it be vertical so the height may be reduced by about 1/3. I am not sure what the folded section does for it. but without the 1/2 wave section coming back down from the top, the antenna is just a J-Pole. The Slim Jim appears to be identical to the "top wire double radiator" J-pole which is described in Cebik's multi-part discussion of J-pole designs: see http://www.cebik.com/vhf/jp2.html His analysis suggests that the performance and behavior of this type of J-pole are essentially identical to those of a single-radiator J-pole. There are some slight changes needed in the antenna dimensions to get it resonated properly (the coax attachment point is a fraction of an inch higher up and the total length is a bit different) but once those are taken into account there doesn't seem to be any real difference in performance between this variant, a version with two wires which are left unconnected at the top, and a version with one wire. At their best, they appear to be simple 1/2-wave radiators. The hype on the HamUniverse page about this antenna outperforming "1/2wave over 1/2wave over 1/2wave colinear!" seems a bit overdone - if it's ever true, it would be in comparison to a rather badly-done colinear! My expectation is that one could create a helically-wound version of any of these J-pole versions. The matching arrangement would no doubt need some adjustment. I'd expect the gain to drop off, with more high-angle radiation appearing, in the usual fashion as the total length of the radiating section is shortened. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Buck wrote:
The SlimJim resembles the J-Pole. And the Zepp. I am not sure what the folded section does for it. Folding a 1/4WL vertical raises the feedpoint impedance. Folding a 1/2WL vertical lowers the feedpoint impedance. A folded 1/2WL monopole has about half the end-fed feed- point impedance of an end-fed single-wire 1/2WL monopole. About 1250 ohms Vs 2500 ohms for 20m with mininec ground. EZNEC sez the folded 1/2WL monopole has a slightly lower resonant frequency and slightly higher gain. (+0.07 dB) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Interesting... so electrical length is affecting gain and EZNEC supports
it--that will probably silence those who claim the physical length is all important... ya suppose? Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw aboot speel-checkin it fer me? "Cecil Moore" wrote in message ... Buck wrote: The SlimJim resembles the J-Pole. And the Zepp. I am not sure what the folded section does for it. Folding a 1/4WL vertical raises the feedpoint impedance. Folding a 1/2WL vertical lowers the feedpoint impedance. A folded 1/2WL monopole has about half the end-fed feed- point impedance of an end-fed single-wire 1/2WL monopole. About 1250 ohms Vs 2500 ohms for 20m with mininec ground. EZNEC sez the folded 1/2WL monopole has a slightly lower resonant frequency and slightly higher gain. (+0.07 dB) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
An 1/2WL end-fed with 1/4WL matching section is a Zepp.
Well yea, I realize that...But I think it's a silly way to do things, if height is an issue...Unless maybe, it's some kind of parallel stub as in a J pole...But I would think that would be sort of silly too... MK |
The SlimJim resembles the J-Pole. The 1/4 wave section is a matching
network and it is probably not critical that it be vertical so the height may be reduced by about 1/3. I am not sure what the folded section does for it. but without the 1/2 wave section coming back down from the top, the antenna is just a J-Pole. Yea, I finally realized that, after Cecils reply. I would still prefer a gamma loop feed I think...MK |
On Mon, 28 Mar 2005 18:21:52 -0800, "John Smith"
wrote: Interesting... so electrical length is affecting gain and EZNEC supports it--that will probably silence those who claim the physical length is all important... ya suppose? Hi "Fred," It will take more than supposition and superstition. So back to rote: The physical size in relation to wavelength dominates launch characteristics, NOT electrical length. 73's Richard Clark, KB7QHC |
"Richard Clark"
So back to rote: The physical size in relation to wavelength dominates launch characteristics, NOT electrical length. __________________ I don't know who wrote your rote, but here is part of what Terman says on this topic in his Radio Engineer's Handbook, p 795, referring to vertical radiators driven against ground: "Top loading has the same effect on the field distribution in a vertical plane as a greater height. Thus an antenna for which H = 0.45 lambda can by suitable top loading be made to have a field distribution in the vertical plane that is substantially the same as for a vertical wire of H = 0.6 lambda." Or is that what you meant? RF |
"Richard Fry" wrote So back to rote: The physical size in relation to wavelength dominates launch characteristics, NOT electrical length. __________________ I don't know who wrote your rote, but here is part of what Terman says on this topic in his Radio Engineer's Handbook, p 795, referring to vertical radiators driven against ground: "Top loading has the same effect on the field distribution in a vertical plane as a greater height. Thus an antenna for which H = 0.45 lambda can by suitable top loading be made to have a field distribution in the vertical plane that is substantially the same as for a vertical wire of H = 0.6 lambda." ============================= No, it doesn't ! But you could stretch "substantial" (a non-engineering term) a bit more. You have been warned once before about quoting Terman as the Bible. (smiley) ---- Reg. |
John Smith wrote:
Interesting... so electrical length is affecting gain and EZNEC supports it--that will probably silence those who claim the physical length is all important... ya suppose? The important point is that the web page claim of bettering three end-to-end 1/2WL dipoles misses by about 3 dB and a few degrees on TOA. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
"Reg Edwards" wrote about the elevation pattern of a loaded vertical against
ground as being ~ the same as that of a longer, unloaded vertical, per Terman: No, it doesn't ! You have been warned once before about quoting Terman as the Bible. ______________ I wonder, then, what your basis is for saying so. At least I give a source. Terman also publishes a formula to calculate the elevation pattern of a shortened vertical with a top-mounted capacity ring, driven against ground -- but it's too much to post here without mathematical notation. The formula was credited by Terman to George H. Brown from his "A Critical Study of Broadcast Antennas as Affected by Antenna Current Distribution" published in the Proceedings of the I.R.E. Terman also says that inserting a coil a bit down from the top of a shortened vertical gives results equivalent to using a top mounted capacity ring. RF |
On Tue, 29 Mar 2005 10:38:49 -0600, "Richard Fry"
wrote: Terman also says nothing about a Helical wound slim jim. Of course, this begs the question "Why would he?" The results are predictable, boringly so, and several have already been down that road to no net gain. However, common sense in these matters can be discarded if only someone offers validation, however slim that may be from any jim. Such inventors stand on the shoulders of dwarfs. Sorry for the allusion, as it again reprises the obvious that physical height in relation to a standard (wavelength) dominates the principle. However as principles and seeking validation go, no doubt the topic will drift towards top loading dwarfs.... 73's Richard Clark, KB7QHC |
Apparently, I am not like you, I don't have all the answers and am just
sitting here ready to educate all the poor ignorant masses who have questions. I am amazed my motives can even be brought into question, to the intelligent, I have suspected would be obvious. I am interested in what others know, or think they know--I am interested in things I do NOT yet know.. While if I am able to help someone with information in my possession--I will quite willingly do so, however, I first need to gain this information. Somehow, from all your posts, I am left with the impression you were probably born knowing all the answers and, if not, you are now in the possession of such and, all others serve only as an anoyance to you--so I can see how you would puzzle over some ignorant A$$ such as myself. Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw aboot speel-checkin it fer me? "Richard Clark" wrote in message ... On Sat, 26 Mar 2005 18:00:30 -0800, "John Smith" wrote: Rather, back to my original question (your ADD--attention defecit disorder is showing), "Anyone ever done a helical wound "Slim Jim?"" Hi "Jack," I suppose it has to be said if this is going anywhe Yes. Is this 20 questions, or do you have any answers for yourself? 73's Richard Clark, KB7QHC |
"Richard Clark" wrote:
Sorry for the allusion, as it again reprises the obvious that physical height in relation to a standard (wavelength) dominates the principle. However as principles and seeking validation go, no doubt the topic will drift towards top loading dwarfs... _____________ So far you have not provided support for your statements on this subject from any recognized antenna authority. Do you really believe that your understanding of this, and your statements about it are better/more accurate than those of Frederick Terman and George Brown? RF |
I must point out that although my exchange with you has been short and
seemingly pointless; you feel a necessity to place yourself in prominence, of both your "knowledge", opinions and your person. I hardly wish you to keep up with such tiring and pointless expenditure of energy on your part--I have found you to only be self-serving in your devotion to your ego, yourself and your personal endeavors to make a fool of yourself and destroy any sense of dignity one might have been able to afford you. I can only speak for myself of course, but you have completely destroyed any credibility I could have granted you and, would only accept any offerings from you after having checked them through other sources--since this is the case, little is to be had from giving you any further considerations at all. Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw aboot speel-checkin it fer me? "Richard Clark" wrote in message ... On Tue, 29 Mar 2005 10:38:49 -0600, "Richard Fry" wrote: Terman also says nothing about a Helical wound slim jim. Of course, this begs the question "Why would he?" The results are predictable, boringly so, and several have already been down that road to no net gain. However, common sense in these matters can be discarded if only someone offers validation, however slim that may be from any jim. Such inventors stand on the shoulders of dwarfs. Sorry for the allusion, as it again reprises the obvious that physical height in relation to a standard (wavelength) dominates the principle. However as principles and seeking validation go, no doubt the topic will drift towards top loading dwarfs.... 73's Richard Clark, KB7QHC |
On Tue, 29 Mar 2005 12:34:08 -0600, "Richard Fry"
wrote: So far you have not provided support for your statements on this subject from any recognized antenna authority. Do you really believe that your understanding of this, and your statements about it are better/more accurate than those of Frederick Terman and George Brown? Hi OM, What you demand is simply a lazy form of leaning on authority without presuming to investigate the principles involved. I am not interested in top loading dwarfs or in replacing simple insights with name dropping and personalities. 73's Richard Clark, KB7QHC |
"Richard Clark" wrote
So far you have not provided support for your statements on this subject from any recognized antenna authority. Do you really believe that your understanding of this, and your statements about it are better/more accurate than those of Frederick Terman and George Brown? What you demand is simply a lazy form of leaning on authority without presuming to investigate the principles involved. I am not interested in top loading dwarfs or in replacing simple insights with name dropping and personalities. ________________ From your post above we must take it that you have investigated what Brown/Terman have to say on this subject, and can prove them wrong. If you wish your statements to be believed above theirs, you will need to show your work. Immortality awaits. RF |
John
Cut off the conversation, it is not worth it. Richard just loves to fight and show how smart he is and if this doesn't work, which is generally, the case he goes on a personal attack. Generally he is not worth the attention. And the more agitated he gets the more he reverts to use of the long words instead of short words and scrambles his answers so all are confused as to what he is saying, why he is saying it as well as what benefit he thinks he is supplying by typing it. The bottom line is that his intention is to destroy the integrity of his opponent rather than to assist with courtesy. And rest assured, he views all as an oponnent Just making a point No reply required Regards Art "John Smith" wrote in message ... Apparently, I am not like you, I don't have all the answers and am just sitting here ready to educate all the poor ignorant masses who have questions. I am amazed my motives can even be brought into question, to the intelligent, I have suspected would be obvious. I am interested in what others know, or think they know--I am interested in things I do NOT yet know.. While if I am able to help someone with information in my possession--I will quite willingly do so, however, I first need to gain this information. Somehow, from all your posts, I am left with the impression you were probably born knowing all the answers and, if not, you are now in the possession of such and, all others serve only as an anoyance to you--so I can see how you would puzzle over some ignorant A$$ such as myself. Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw aboot speel-checkin it fer me? "Richard Clark" wrote in message ... On Sat, 26 Mar 2005 18:00:30 -0800, "John Smith" wrote: Rather, back to my original question (your ADD--attention defecit disorder is showing), "Anyone ever done a helical wound "Slim Jim?"" Hi "Jack," I suppose it has to be said if this is going anywhe Yes. Is this 20 questions, or do you have any answers for yourself? 73's Richard Clark, KB7QHC |
Wasn't George Brown one of the ancient trio of experimenters who laid
out 118.5 radials but all three forgot to measure the most important characteristics - ground conductivity and permittivity! |
John, I just love your logical assembly and choice of words. It flows.
Too good for amateur radio. I wish I had your vocabulary. ---- Reg. |
On Mon, 28 Mar 2005 18:21:52 -0800, "John Smith"
wrote: Interesting... so electrical length is affecting gain and EZNEC supports it--that will probably silence those who claim the physical length is all important... ya suppose? Regards ..07 DB might be gain, but I somehow get the feeling that I would never notice it on my HF rig. What would that gain represent on a 1000 watts? I don't know the formula, just the generalization that 3 db = double power. -- 73 for now Buck N4PGW |
True, it is only "proof of concept." However, the longest journey begins
but with the first step... Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw aboot speel-checkin it fer me? "Buck" wrote in message ... On Mon, 28 Mar 2005 18:21:52 -0800, "John Smith" wrote: Interesting... so electrical length is affecting gain and EZNEC supports it--that will probably silence those who claim the physical length is all important... ya suppose? Regards .07 DB might be gain, but I somehow get the feeling that I would never notice it on my HF rig. What would that gain represent on a 1000 watts? I don't know the formula, just the generalization that 3 db = double power. -- 73 for now Buck N4PGW |
In some situations it is better to have a 'shortened' antenna than the
absolute last tiniest fraction of a db. I realize a cap hat can reduce the size of a vertical with reasonably low loss, I am wondering if it would do as well with the J-Pole? For example, a quarter wave matching network for the J-Pole would be whatever works best, be it original design or some form of balun, but the 1/2 wave vertical might be reduced in size by forming a capacity hat above it. How well would that work for shortening a J-Pole? would it be better to use a shortened 1/2 wave dipole or would the J-Pole design be better? Buck -- 73 for now Buck N4PGW |
Becareful Buck!!! It is catching, you are starting to think like me!
Regards -- Hay, if'n ya'll cun't konstructivly partecipete in this har disscusion, haw aboot speel-checkin it fer me? "Buck" wrote in message ... In some situations it is better to have a 'shortened' antenna than the absolute last tiniest fraction of a db. I realize a cap hat can reduce the size of a vertical with reasonably low loss, I am wondering if it would do as well with the J-Pole? For example, a quarter wave matching network for the J-Pole would be whatever works best, be it original design or some form of balun, but the 1/2 wave vertical might be reduced in size by forming a capacity hat above it. How well would that work for shortening a J-Pole? would it be better to use a shortened 1/2 wave dipole or would the J-Pole design be better? Buck -- 73 for now Buck N4PGW |
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