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Al:
This room is less about antennas than it is about egos, hero worship, and the "good ole boys club." I have seen egos here large enough to chase all the air from the room--leaves one breathless... a couple of these guys are even "LEGENDS IN THEIR OWN MINDS!", now that's gotta count for something! Perhaps we will eventually get some 25 to 45 year olds in here and restore some progressive thinking, discussion, debate and argument which civilized men can conduct in productive ways... those who have had their day in the sun (or 15 minutes of fame) will eventually move on. Right now, there is little point in fighting the "status quo" here--they turn like a pack of wild dogs in attack if even someone poses an original thought, or explores an unconventional path... one poor long tall drink of water from Texas is taking his lickings for this now. It does have the effect of chasing off fresh new minds which would be of interest to us who would enjoy group participation--rather than a lecture by a dinosaur (and I can say that even being close to "dinosaur age" myself.) Hang in there OM... if you have measured those swr's and know your product, people will give it a go... .... the construction seems well done and should provide service for many years... Should be more than satisfactory for someone just wanting to get on the band(s) and not become an antenna guru. Heck, with an L-Match on it a guy might be surprised how wide that bandwidth can become... Warmest regards, John "Al" wrote in message oups.com... Hey Al, Don't let the nay-sayers in this NG bother you, and don't waste your time arguing with them. Some of them can't stand the thought that any antenna which differs from their personal pet(s) might be good. Others can't grasp the idea that when model predictions and actual results differ, it's the results that count. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Your antenna is beautifully made, very reasonably priced, and you are (apparently) making a successful small business with it. Your customers are delighted, and refer their friends. You are starting to attract imitators. How many of these accomplishments can the nay-sayers claim? Keep up the good work... the XYL and I love our three OSJs! And they are now pretty much standard in our ARES/RACES organization. NO complaints heard to date. Thanks, Ed, W6LOL You are absolutely right. There is an old saying "You can't please all the people all the time". That's why I put the Money Back Guarantee on everything I sell. The return rate is less than 1 in 1,000 units sold. That's good enough for me. That's it, I am done. Thanks for all the fun. 73 Al Lowe N0IMW |
Again, I just think it is wrong to tell someone the antenna won't work
with out a choke. Well, obviously I've never said that. But I have done many tests with 1/2 waves with and without decoupling sections. They were always improved with the extra section. I just mainly wanted to clarify that no matter how the antenna is fed, or no matter the SWR, which is totally irrelevant, you still have to contend with the spillover currents. The only cure for that is a decoupling section, choke, or whatever. As far as I know, the isopole was electrically the best dual 5/8 ever built as far as decoupling the line. I've never heard of any competing designs beating it. The ringo ranger II is slightly inferior. But the isopole is also pretty ugly...Looks like a missile... I'm not saying it doesn't work ok now. I'm sure it does. I'm just saying it would likely work a bit better with it, and be more stable as far as common mode currents per users at different sites. I agree. I don't think you should change it...There are other designs if you want higher performance..Anyone wanting to further decouple the line can add their own chokes, etc.. The ringo ranger II was cushcrafts answer to the isopole. Before that, they sold the ringo ranger. It was basically fed the same way as the J pole, except using the gamma loop. Like the version you use, the gamma loop ain't half bad at decoupling the line in itself. It was fairly usable as is, and many used it for a few years...Then the isopole came out, with basically the same dual 5/8 design, but with decoupling. It just tore the ringo ranger a new one... Smoked it....Cushcraft knew they had a major problem. So they designed a decoupling section to add below the regular ringo ranger. Made a *huge* difference in performance for most users. I know myself, I tested it with and without the decoupling section, just out of curiosity. On local repeaters, the average difference was 3-4 S units, using an icom 22u. And thats totally reciprical. On VHF/UHF, I've found that decoupling is generally more important to low angle gain, that any gains from element lengths, or collinears, etc... A well decoupled 1/4 wave ground plane can easily match or beat a poorly decoupled much taller ringo ranger with no section... Myself....I prefer a small yagi....:/ I have a three el for FM, vertical... Smokes any vertical....MK |
Don't let the nay-sayers in this NG bother you, and don't waste
your time arguing with them. At this point, I don't consider my thoughts, arguing.... Just stating the fairly obvious...Don't ignore spillover currents if you want superior performance from an elevated vertical on VHF/UHF. Some of them can't stand the thought that any antenna which differs from their personal pet(s) might be good. I could care less...He didn't invent the J pole... Others can't grasp the idea that when model predictions and actual results differ, it's the results that count. The actual results count...I could care less about the models. I've tested all this in the real world, with real antennas. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Total BS in most cases....I seen the lack of decoupling totally ruin otherwise decent antennas... I've personally tested and seen easy 3-4 s unit differences in the same exact antenna , with and without the decoupling section connected. Decoupling is critical to high performance on VHF/UHF. All the best designs include it. Your antenna is beautifully made, very reasonably priced, and you are (apparently) making a successful small business with it. Your customers are delighted, and refer their friends. Yes, I agree. I know many people that use his arrow yagi's for SAT work...Just because his J pole doesn't have a decoupling device doesn't mean he doesn't build good antennas...Not that many people decouple J poles...I've never understood why...But there it is... You are starting to attract imitators. The J pole has been imitated numerous times.... Or are you talking about arrows? How many of these accomplishments can the nay-sayers claim? Ugh....I'm not in the antenna biz...But If I were....but If I were.... I would decouple *all* my VHF/UHF verticals. Myself, I doubt I would even sell a J pole... I'm not particularly fond of the design... I would sell a super duper isopole II..... Decoupling out the ying yang... And yes, I'm sure it would cost more than $39.00... MK |
The biggest problem I have run into with your J-pole is that it sets up a
lot of wind vibration noise at 70 MPH when mounted on the roof of my Subaru. :) "Al" wrote in message oups.com... Sniped I don't believe you can totally eliminate all current. There will always be a small amount. Agreed, but it is small enough I don't think most people could see a difference in performance if it had a choke or not. All I am saying, to say the antenna won't work with out a choke is just wrong. I doubt I would change the antenna....Would make it cost more... I'd consider a super deluxe version for a higher price, if they wanted full 2 section decoupling...:/ And if I went that far, I'd use a dual 5/8 design to get more gain. You'd be reinventing the isopole...:/ MK I have an "Isopole" here in the shop, it works good, maybe one of the best 5/8 wave antennas I have ever tested. I think it could be built a little better. I have seen a lot of them that were broke. But that is comparing apples to oranges The OSJ is a simple 1/2 wave antenna that has 0 dBd gain. No magic. Again, I just think it is wrong to tell someone the antenna won't work with out a choke. 73 Al Lowe N0IMW |
nm5k:
I agree with you on some you say, and on some of it disagree... Some, like me, care most about getting something up you can use and/or tinker with... and I work with computer models all day, I like to get my hands dirty... Others want it to be perfect "on paper"... This is not a case of one being right over the other--and no matter what their goal--I would like to accept it as a valid goal without question. It helps to try to formulate answers to help the particular person in question towards obtaining their goals--as opposed to impressing them with ones personal knowledge--well, unless that is what they wish and/or that is acceptable to them. There are men with good sound knowledge here, I do not question that--just sometimes they could present it in a manner which is more pleasant and tolerant... either way I will accept it, however I think some of the "faint at heart" are chased away... And in any case, it does not hurt to know the fine details of something--take the balun/choke and feedline currents for example--heck, you can run with the currents... and, if you ever get tired and wonder what it would be like to run without them, doesn't hurt to have gained the knowledge to quickly wind a current balun and chuck it in the line... Warmest regards, John wrote in message oups.com... Don't let the nay-sayers in this NG bother you, and don't waste your time arguing with them. At this point, I don't consider my thoughts, arguing.... Just stating the fairly obvious...Don't ignore spillover currents if you want superior performance from an elevated vertical on VHF/UHF. Some of them can't stand the thought that any antenna which differs from their personal pet(s) might be good. I could care less...He didn't invent the J pole... Others can't grasp the idea that when model predictions and actual results differ, it's the results that count. The actual results count...I could care less about the models. I've tested all this in the real world, with real antennas. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Total BS in most cases....I seen the lack of decoupling totally ruin otherwise decent antennas... I've personally tested and seen easy 3-4 s unit differences in the same exact antenna , with and without the decoupling section connected. Decoupling is critical to high performance on VHF/UHF. All the best designs include it. Your antenna is beautifully made, very reasonably priced, and you are (apparently) making a successful small business with it. Your customers are delighted, and refer their friends. Yes, I agree. I know many people that use his arrow yagi's for SAT work...Just because his J pole doesn't have a decoupling device doesn't mean he doesn't build good antennas...Not that many people decouple J poles...I've never understood why...But there it is... You are starting to attract imitators. The J pole has been imitated numerous times.... Or are you talking about arrows? How many of these accomplishments can the nay-sayers claim? Ugh....I'm not in the antenna biz...But If I were....but If I were.... I would decouple *all* my VHF/UHF verticals. Myself, I doubt I would even sell a J pole... I'm not particularly fond of the design... I would sell a super duper isopole II..... Decoupling out the ying yang... And yes, I'm sure it would cost more than $39.00... MK |
This room is less about antennas than it is about egos, hero worship,
and the "good ole boys club." Speak for yourself....I rarely deviate from the topic of the NG...On the other hand....That John Smith/Bret dude often goes off on weird tangents....... Hang in there OM... if you have measured those swr's and know your product, people will give it a go... SWR has absolutely nothing to do with common mode currents.. Even someone just wanting to get on the band(s) should be aware of that. It's for their own good. MK |
.... what is never GOOD is having another tell one WHAT IS GOOD for
them... if you do that in normal life, expect to get told off as often as here... John wrote in message oups.com... This room is less about antennas than it is about egos, hero worship, and the "good ole boys club." Speak for yourself....I rarely deviate from the topic of the NG...On the other hand....That John Smith/Bret dude often goes off on weird tangents....... Hang in there OM... if you have measured those swr's and know your product, people will give it a go... SWR has absolutely nothing to do with common mode currents.. Even someone just wanting to get on the band(s) should be aware of that. It's for their own good. MK |
what is never GOOD is having another tell one WHAT IS GOOD for
them... if you do that in normal life, expect to get told off as often as here... What is good is talking to people that don't have their heads up their rearend. All I'm doing is stating fairly simple facts. If you choose to ignore them, fine with me... But don't start with your goofball behavior pattern just because I'm trying to clarify that *no* type of feed on an elevated vertical is capable of fully decoupling the antenna on it's own. I quote from Al's first post.... "One think you may have missed, the original post was about a Arrow Antenna J-Pole. This is an Open Stub type J-Pole, Not a Closed Stub type like the copper pipe ones. The OSJ does not need a choke, it does not have a problem with feedline radiation or a problem with Common Mode Currents. " That statement is *false* if you want the best performance. That type of antenna is most certainly able to suffer from feedline radiation. Sure, it may be better decoupled from the line using his method vs another, but that does not deal with spillover currents. There must be a 2nd decoupling device to deal with those currents. The antenna does include that as sold. If you think I really give a hoot about Arrow antennas, or Al, or whoever, you are sadly mistaken. He would have never heard from me if he hadn't said that his J pole can't suffer from common mode problems. I'm a dumbass compared to many of these people, and even I know thats a silly statement to make, unless you like holes in your toes. Oh...And I can't ever recall ever being "told off" on any post, on any NG...I don't have the behavior patterns, hyperactivity, etc, that you seem to exhibit. So I don't attract the attention that people like you do. The only people that ever get me going are smartasses. I have run across 4-5 real=AE smartasses on my journey through the internet. They tried to tell me off, but I quickly showed them that that was an effort in futility. I'm rated a black belt when it comes to smartasses. You wanna be #6 on the list? Go ahead...Make my day.... At this point, I don't consider you a full fledged smartass... You are like a 9 year old that is hyperactive from gorging on chocolate, that turned out to actually be coated preluden pills... So I cut you a bit of slack...So far.....Don't push your luck... You would have never heard from me, except that your post struck me as overall BS...As usual.... Note... This room is less about antennas than it is about egos, hero worship, and the "good ole boys club." Only people that are defensive, or are trying to cover something up, or trying to claim some silly nonsense would feel this way. All people have ego's to varying degrees. Best to ignore.... I would never worship a man. I don't belong to any clubs, but I reckon if I did, I would prefer a bunch of good ole boys, over a bunch of anal retentive "girly men" who constantly feel victimized by the world in general... MK |
In article ,
Wes Stewart wrote: But he says, "However, since the currents on either side of the feedpoint are not balanced, a choke balun is mandatory to suppress unwanted currents on the feedline." Whups, you're right. I though that this particular section of his text was referring to the standard J-pole, but in re-reading it I see that it's referring to the nonstandard/open-sleeve version. Cebik's model would need to be modified somewhat apply to the Arrow open-sleeve J-pole, as the Arrow is fed at the very base of the one element rather than halfway between the two. That's how I modeled it, although it makes very little difference in the results. Since it's only an inch or so, that makes good sense. Anybody care to model up the Arrow, with all three elements included, with and without a separate wire representing the outside of the coax? Done, before you asked.[g] That's what the Howard/Fine/Howard team used to call "Super Service!" :-) -- 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! |
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Again, I just think it is wrong to tell someone the antenna won't work with out a choke. 73 Al Lowe N0IMW I agree entirely. In fact, I think it's wrong to tell someone that an antenna won't "work", regardless of how good or bad it is. The only exception I'd make is if the person has some very well-defined criteria about what constitutes "working" and what doesn't, but very few people do. Most hams want to talk to someone, and most antennas will allow them to do that, with a minimum of fuss, optimizing, or knowledge -- that is, most antennas "work". Once that basic need is met, durability, construction quality, and customer support rightfully become the most important items in choosing a commercial antenna. Just about any antenna can be made to work better in a technical sense (for example, higher gain in some direction). But a technical improvement that doesn't cause any improvement in operational use isn't an improvement at all. If the repeater you want to talk to is full quieting in both directions, no technical improvement in the antenna will improve your ability to communicate, so there's no point in putting forth the effort. Who cares if your car can go 120 or 140 MPH if you never drive it over 70? [Considering the giant immaculate scratch-free four-wheel drive vehicles overpopulating the suburban roads, I'm afraid that's not a good example.] On the other hand, if you're trying to operate under marginal conditions, even a small technical improvement in the antenna performance translates to an enhanced ability to communicate. That's where it pays to know something about how antennas work, and where it can be worth the time and trouble to make the improvements. I have to say, though, it's sometimes discouraging when suggestions about how an antenna can be improved are interpreted as saying an antenna "doesn't work" without the improvements. It's awfully hard to penetrate through the binary way of thinking most people seem to be stuck with. It's really a shame that some manufacturers of good, serviceable, durable antennas feel they have to create some special and magical quality to convince people to buy their products. But I guess that's the reality of the marketplace. Works for cars, works for medicine, must work for antennas too. Roy Lewallen, W7EL |
As an alternative to using a choke on the feedline, what sort of
results might one get with a standard J-pole by using a half-wave coaxial balun and tapping up a bit further on the elements? Still don't think that would clean up spillover currents... If I were to use a J pole, and wanted decoupling, I would add a 1/4 wave coax section below the feed, and then have a set of radials at that point. They can be grounded to the mast, or left free, as long as they are connected to the shield. The 1/4 wave of coax is physical length, not electrical. But I've found in testing, it's not all that critical. Of course, he wouldn't be able to claim "no radials" at that point, but it would be pretty well decoupled. This is the same basic design cushcraft used with the ringo ranger. In that case, the coax length was 50 inches long, to a set of 20 inch radials. They used the longer length due to the dual 5/8 design. They actually seem to claim that 50 inches of coax as a 3rd radiating element, but I don't quite see it that way. If that were truly the case, it would beat the isopole. The comparison between the isopole and the ringo ranger 2 show how important decoupling is. They are both appx dual 5/8 designs. No real difference in element length. The isopoles improved decoupling is what make it the winner when you compare the two head to head. A sleeve would also be easy to use with a J pole... Actually, I sort of prefer the center fed 1/2 wave "sleeve" dipole vertical, with a 2nd lower decoupling sleeve, over the usual J pole design. MK |
Ian, not wishing to be classed amongst the old wives you have very carefully avoided talking about "power radiated from feedlines". You have shifted to using clamp-on ammeters. But people who DO discuss things in such terms are unable to justify the use of chokes by quantifying the power actually radiated and setting limits on what power level is acceptable or is not acceptable. If they can't measure or calculate the power level then they know nothing about what they are are talking. Refer to what Lord Kelvin said about measurements. Can you suggest an acceptable level of amps as measured on a clamp-on ammeter? ---- Reg, G4FGQ ---------------------------------------------------------------------- --------- "Ian White GM3SEK" wrote in message ... Reg Edwards wrote: They who discuss "power radiated from the feedline", yet are unable to measure (in watts) or calculate (in watts) the MAGNITUDE of the effect, belong to a set of waffling old wives. Those who take no precautions to prevent their feedline from becoming part of the antenna, belong to a set of people who don't even know what their antenna IS. There's a part you call "the antenna", and another part you call "the feedline". Wishful thinking will not stop RF current from flowing directly from one to the other. How is it possible to decide whether or not a choke or balun is needed, and where to locate it, unless the magnitude of what one MIGHT wish to prevent is known. Try a clamp-on RF current meter, a little modeling... or even a little common sense. There's a place called "the feedpoint" where the antenna and the feedline are connected directly together. Might that be a good location for a choke to keep them separate? Yes, it almost certainly would. Chokes may also be needed at other locations, but it's hard to justify anywhere else as your *first* choice. (The exception is the Carolina Windom and similar antennas where part of the feedline is intended to radiate. But even there, they put a good choke at the point where they want RF currents on the feedline to stop.) Queen Elizabeth 1 of England had the good sense to take a bath every six months "whether I need it or not". If you don't know whether your feedline smells of RF, then follow her excellent advice and use a choke. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Dave Platt wrote:
In article , Ian White GM3SEK wrote: The version of the "non-standard J-pole" which Cebik models is fed at bottom center, in a dimensionally-symmetrical way. His current plot seems to show equal currents at this feedpoint, and this would seem to make the use of a choke or balun on the feedline somewhat less significant than with a standard J-pole. An antenna model without a feedline will *force* equal and opposite currents at the feedpoint - it is always fed through the perfect balun! Cebik's plot of currents in the "standard" J-pole shows unequal currents all the way down to the bottom, and he notes this in his text and asserts the need for a choke. He doesn't say whether his models do or do not include a feedline. If they did, the configuration of the feedline would become another important variable which he couldn't fail to mention. Also the drawings show no feedline. Add an un-choked feedline to the model (another thick wire, representing the coax shield) at either side of the feedpoint, and see where the current goes now. If you don't use a choke on a real-life antenna, there's nothing to stop the current going wherever it likes. Agreed. The results are likely to be quite variable depending on the feedline distance to the nearest ground. Seems to me that the worst case would result from a small integral multiple of 1/2 wavelength, no? That's right. At the point where the coax shield connects to the antenna, the current will divide three ways, between the antenna, the inside of the shield, and the outside of the shield. The split will depend on the ratio of the impedances in each of those three directions. If the impedance for current flowing down the outside of the shield is low (which any multiple of 1/2 wavelength grounded at the bottom will achieve) then away the current will go - there's nothing to stop it. A feedline choke creates a high impedance against current flow down the outside, so the current from the inside of the shield flows almost exclusively into the antenna. Even if you choke a J-pole at the feedpoint, there will also be induced currents further down the feedline because the antenna and the feedline are usually installed in a straight line. But that doesn't override the need to choke the feedline at the most obvious place. My guess is that in most simple J-pole installations, the feedline radiation and the resulting disturbance of the antenna's omni pattern are probably not going to be worth worrying about too much. Nearby buildings, trees, etc. are likely to result in larger differences in the far-field pattern than any quirks in the antenna's own pattern. Most people using J-poles won't worry, that is true... but that's mostly because J-poles are used in relatively undemanding applications where you either hit the repeater or packet node, or you don't. In defence of Al, if the J-pole is mounted directly on a car roof, then there's no point in attempting to choke the feedpoint. But if it's mounted on a mast, the mast and feedline will radiate. How much will depend on the exact installation, and is pretty well unknown unless you can measure the actual RF currents. As an alternative to using a choke on the feedline, what sort of results might one get with a standard J-pole by using a half-wave coaxial balun and tapping up a bit further on the elements? That is a workable feed method, but the half-wave balun is a voltage balun. The antenna is asymmetrical, so the balun is acting as center-tapped voltage source which is trying to push equal currents into the unequal impedances on either side of the feedpoint. That will never quite succeed, so there will always be some out-of-balance current left over. Like all voltage baluns, the half-wave coax type doesn't do anything directly to *prevent* the out-of-balance current from flowing away on the outside of the feedline. On the contrary, there is a hard-wired connection that will *allow* such currents to flow. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Reg Edwards wrote:
Ian, not wishing to be classed amongst the old wives you have very carefully avoided talking about "power radiated from feedlines". You have shifted to using clamp-on ammeters. But people who DO discuss things in such terms are unable to justify the use of chokes by quantifying the power actually radiated and setting limits on what power level is acceptable or is not acceptable. If they can't measure or calculate the power level then they know nothing about what they are are talking. That's not really quite true. Can you or anyone else tell how many watts is radiated from each element of a Yagi? How? Then how do you know which elements are important an which are not? Roy Lewallen, W7EL |
Reg Edwards wrote:
Ian, not wishing to be classed amongst the old wives you have very carefully avoided talking about "power radiated from feedlines". You have shifted to using clamp-on ammeters. But people who DO discuss things in such terms are unable to justify the use of chokes by quantifying the power actually radiated and setting limits on what power level is acceptable or is not acceptable. If they can't measure or calculate the power level then they know nothing about what they are are talking. Refer to what Lord Kelvin said about measurements. Can you suggest an acceptable level of amps as measured on a clamp-on ammeter? No. Reg knows perfectly well that the RF current is only one part of a much bigger picture. An acceptable level is one that: 1. Does NOT make the microphone bite your lips (or does not leave lasting scars :-) 2. Does NOT cause your transmitter to act up because there's too much RF current flowing through your station, trying to find "ground" 3. Does NOT cause RFI to your family and neighbours 4. Does NOT cause unpredictable changes in transmitter loading 5. Does NOT lead to unacceptable pickup of interference when you're trying to receive. So that "acceptable level" depends entirely on each individual's particular station layout, how they operate, where they live, what kinds of consumer electronics the family and neighbours use, how they are installed... and how much that individual ham cares about getting along with the family and the neighbours. Every case is totally individual. That is why every individual needs to do his own thinking and make his own decisions. The only "old wives' tale" is that somebody else can do it for you, or tell you from 5000 miles away what does or doesn't matter. You don't actually need to measure amps in order to make those decisions. Basically it's all about simple practical things like the list above. Where the RF current meter really helps is if you decide you do have an RFI problem. Then it lets you *see* how well you're managing to fix it. Too much of RFI investigation work is like groping in the dark. The RF current meter is like taking a blindfold off. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
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That's not really quite true. Can you or anyone else tell how many
watts is radiated from each element of a Yagi? How? Then how do you know which elements are important an which are not? Roy Lewallen, W7EL ================================ Neither you, I or anybody else knows. But, as usual, you have put your finger on the source of the trouble. It's a descriptive language problem. To speak in terms which most people understand, when Cecil acquired his burn the injury was just as likely to come from the antenna as it was from the feedline. Actually, it came from the PA via the tuner. It is not entirely unrelated to the confusion about standing waves caused by referring to the so-called SWR meter as an SWR meter, when it doesn't do anything of the sort and, in any case, there is no line in a position on which SWR can be measured. ---- Reg, G4FGQ |
Ian White GM3SEK wrote:
Where the RF current meter really helps is if you decide you do have an RFI problem. Then it lets you *see* how well you're managing to fix it. Too much of RFI investigation work is like groping in the dark. The RF current meter is like taking a blindfold off. And the "RF current meter" doesn't have to be expensive or complicated. A before/after relative current value may be all one needs. I use a toroid with ten turns feeding a 1N34A curcuit and a DC voltmeter with very short leads. It was "calibrated" using forward current into a 50 ohm load. Simple measurements like this are covered in, "Baluns, What They Do And How They Do It", by Roy, W7EL, in the ARRL Antenna Compendium, Vol 1, article available at: http://www.eznec.com/Amateur/Articles/ -- 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 =--- |
.... my gawd, you go into far too much verbiage for far too simple of
explanation(s) of your personal, views, beliefs and offerings... I do choose to ignore them and toss 'me into "what nm5k likes" bucket--which frankly, "charlotte--I don't give a damn." .... if the only time you hear these complaints are from me, no need to worry, if others point out your nature is less than desirable (and new members--not the good ole boys here who are into the "mutual admiration societies", "legends of their own mind(s) clubs) then you may want to use it to your advantage--or not... John wrote in message oups.com... what is never GOOD is having another tell one WHAT IS GOOD for them... if you do that in normal life, expect to get told off as often as here... What is good is talking to people that don't have their heads up their rearend. All I'm doing is stating fairly simple facts. If you choose to ignore them, fine with me... But don't start with your goofball behavior pattern just because I'm trying to clarify that *no* type of feed on an elevated vertical is capable of fully decoupling the antenna on it's own. I quote from Al's first post.... "One think you may have missed, the original post was about a Arrow Antenna J-Pole. This is an Open Stub type J-Pole, Not a Closed Stub type like the copper pipe ones. The OSJ does not need a choke, it does not have a problem with feedline radiation or a problem with Common Mode Currents. " That statement is *false* if you want the best performance. That type of antenna is most certainly able to suffer from feedline radiation. Sure, it may be better decoupled from the line using his method vs another, but that does not deal with spillover currents. There must be a 2nd decoupling device to deal with those currents. The antenna does include that as sold. If you think I really give a hoot about Arrow antennas, or Al, or whoever, you are sadly mistaken. He would have never heard from me if he hadn't said that his J pole can't suffer from common mode problems. I'm a dumbass compared to many of these people, and even I know thats a silly statement to make, unless you like holes in your toes. Oh...And I can't ever recall ever being "told off" on any post, on any NG...I don't have the behavior patterns, hyperactivity, etc, that you seem to exhibit. So I don't attract the attention that people like you do. The only people that ever get me going are smartasses. I have run across 4-5 realŪ smartasses on my journey through the internet. They tried to tell me off, but I quickly showed them that that was an effort in futility. I'm rated a black belt when it comes to smartasses. You wanna be #6 on the list? Go ahead...Make my day.... At this point, I don't consider you a full fledged smartass... You are like a 9 year old that is hyperactive from gorging on chocolate, that turned out to actually be coated preluden pills... So I cut you a bit of slack...So far.....Don't push your luck... You would have never heard from me, except that your post struck me as overall BS...As usual.... Note... This room is less about antennas than it is about egos, hero worship, and the "good ole boys club." Only people that are defensive, or are trying to cover something up, or trying to claim some silly nonsense would feel this way. All people have ego's to varying degrees. Best to ignore.... I would never worship a man. I don't belong to any clubs, but I reckon if I did, I would prefer a bunch of good ole boys, over a bunch of anal retentive "girly men" who constantly feel victimized by the world in general... MK |
Cecil Moore wrote:
Ian White GM3SEK wrote: Where the RF current meter really helps is if you decide you do have an RFI problem. Then it lets you *see* how well you're managing to fix it. Too much of RFI investigation work is like groping in the dark. The RF current meter is like taking a blindfold off. And the "RF current meter" doesn't have to be expensive or complicated. A before/after relative current value may be all one needs. I use a toroid with ten turns feeding a 1N34A curcuit and a DC voltmeter with very short leads. It was "calibrated" using forward current into a 50 ohm load. Simple measurements like this are covered in, "Baluns, What They Do And How They Do It", by Roy, W7EL, in the ARRL Antenna Compendium, Vol 1, article available at: http://www.eznec.com/Amateur/Articles/ There are also full constructional details and examples on my site, at: http://www.ifwtech.co.uk/g3sek/clip-on/clip-on.htm -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
How is it possible to decide whether or not a choke or balun is
needed, and where to locate it, unless the magnitude of what one MIGHT wish to prevent is known. I don't know about wattage, but measuring the damage that a lack of decoupling does to the antenna is easy to measure. Quite simple. Try each way, and note the difference on a stable signal. The ringo ranger without the lower section lost 3-4 S units worth of performance in my case, using my line length. Ditto for any other antenna. I found the decoupling of simple 1/4 GP's can be improved also. Many, "including me" often state that once a GP is at say 1/2 wave high, that only 3-4 radials are needed. As far as ground losses, this is true. But the decoupling from the line can be further improved by adding even more radials. Going from 4 radials to 8 usually makes a noticable difference on a receiver...I consider a receiver as just an poorly calibrated voltage meter in this case. It's plenty good enough for A/B comparisons. At HF, I don't worry about feedline radiation too awful much. If I'm not torching my lips, wanking out my keyer, or causing light bulbs to flicker in time to my CW or voice, I'm a happy camper. Not so on VHF/UHF....I consider it critical if you want the best performance. And....All this was tested in the real world by yours truly...Over 20 years ago...I've had plenty of time to change my stance...But I haven't...MK |
wrote:
I found the decoupling of simple 1/4 GP's can be improved also. Quite often, one sees multiple turns of coax looped under commercial elevated ground planes. -- 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 =---- |
Hi MK,
You seem a bit wound up... too much caffeine? ;-) wrote in message oups.com... (snip) Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Total BS in most cases....I seen the lack of decoupling totally ruin otherwise decent antennas... I've personally tested and seen easy 3-4 s unit differences in the same exact antenna , with and without the decoupling section connected. Decoupling is critical to high performance on VHF/UHF. All the best designs include it. Let's see now. You say my proposition that an effect too small to measure doesn't matter is "Total BS in most cases." Then you give an "example" where the effect can not only be measured, but the measured difference is very large "3-4 s unit(s)." This strongly suggests that you did not understand the original premise of "effects too small to measure." So let's try another example, one far removed from antennas. Let's say that ONE dust mite of 1,489,362 on your body at a certain time decides to jump off while you're standing on the bathroom scale--and that this event does not register on the scale. I would say this too-small-to-measure event does not matter in the real world. And even if you found a super laboratory scale that actually could measure the mite departing, I would STILL say the event does not matter. Your mileage may vary, of course. Over in a digital camera forum I frequent, they have coined a term to describe camera geeks who obsess about tiny differences in camera system performance that have no practical significance in real-world picture taking. The term is "measurebator." Perhaps the term would also be useful in this NG. But we'll probably have to add a new one of our own for the guys who think modeling trumps practice. I suggest "modelbator." Last but not least, if someone posts valid data showing that the performance of an OSJ J-pole can be measurably, repeatably, and significantly improved by a decoupling device, I'll be grateful to him/her! And if the decoupling device is practical and affordable, I'll want to know where to buy one, or how to build one. Live long and prosper... (snip) You are starting to attract imitators. The J pole has been imitated numerous times.... Or are you talking about arrows? My reference was to a guy in our area who is making exact mechanical copies of the Arrow design. I suspect there are others doing the same. (snip) MK |
And even if you found a super laboratory scale
that actually could measure the mite departing, I would STILL say the event does not matter. Your mileage may vary, of course. Yes it varies a good deal...I'm not willing to throw away 3-4 S units worth of low angle gain in the case of the ringo ranger. It would take many mites to make up the difference. Of course, the degree would vary to each persons feedline. I was using about 50 ft. Last but not least, if someone posts valid data showing that the performance of an OSJ J-pole can be measurably, repeatably, and significantly improved by a decoupling device, I'll be grateful to him/her! I've tested it, but I didn't collect data, other than in my head. But there is no doubt that adding decoupling would make the performance the same for any user. This will not be the case without it. All decoupling will do is make sure you get the gain you are supposed to. It's not going to help an antenna that has little common mode problem to begin with. I suppose Al would have to have a poll....If the owners were interested in the test...I don't really like J poles that much, so I know I'm not going to waste my time repeating something I did 20 years ago... And if the decoupling device is practical and affordable, I'll want to know where to buy one, or how to build one. I've already described one simple version...I've tested it, and I know it works. There are many ways you can do it.. MK |
On Mon, 13 Jun 2005 22:54:01 GMT, "Old Ed"
wrote: Don't let the nay-sayers in this NG bother you, and don't waste your time arguing with them. Some of them can't stand the thought that any antenna which differs from their personal pet(s) might be good. Others can't grasp the idea that when model predictions and actual results differ, it's the results that count. Spoken like a true naif. I suggest that you would take the time to learn what causes common mode current to be present on coax transmission line - regardless of what kind of an antenna it is employed. (For openers I suggest you start here http://www.w2du.com/r2ch21.pdf ) Then, after getting a grasp on that aspect continue to learn how common mode current on the transmission line can effect the overall performance of an antenna's radiation pattern - especially with VHF & UHF antenna systems then you just might understand what people here are trying to tell you. However, I doubt that you would do that as it would appear you've made up your mind and don't want to be confused with known facts. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Others have measured this and reported it to you, but for some reason you chosen to discount anyone who can show that it disagrees with your "pet" theory. For me, I've place your theory along with the world is flat, the moon is made of green cheese, and Iraq has weapons of mass destruction . But even for a skeptic, I would thing that the thought of coiling up a few turns of coax costs very little, definitely won't hurt, and can only help. Would be sufficient. Danny, K6MHE |
I suggest that you would take the time to learn what causes common
mode current to be present on coax transmission line - regardless of what kind of an antenna it is employed. (For openers I suggest you start here http://www.w2du.com/r2ch21.pdf ) Then, after getting a grasp on that aspect continue to learn how common mode current on the transmission line can effect the overall performance of an antenna's radiation pattern - especially with VHF & UHF antenna systems then you just might understand what people here are trying to tell you. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Others have measured this and reported it to you, but for some reason you chosen to discount anyone who can show that it disagrees with your "pet" theory. For me, I've place your theory along with the world is flat, the moon is made of green cheese, and Iraq has weapons of mass destruction . But even for a skeptic, I would thing that the thought of coiling up a few turns of coax costs very little, definitely won't hurt, and can only help. Would be sufficient. Danny, K6MHE I said I was done with this subject, But ........ I can't take it anymore. Again, the Arrow Antenna OSJ Antenna does NOT need a choke balun. By that I mean it will make no noticeable difference in performance of this particular antenna. (I am not lumping all VHF & UHF antennas together. I am ONLY talking about the OSJ). If you don't have a physical Arrow Antenna OSJ to test with and without a balun, you don't know what you are talking about. That goes for computer modeling also. You can't hook up a radio to computer model. This antenna works just fine the way it is. By the way Danny, what is the name of your Antenna Company ? 73 Al Lowe N0IMW Arrow Antenna |
On 16 Jun 2005 10:29:02 -0700, "Al" wrote:
I suggest that you would take the time to learn what causes common mode current to be present on coax transmission line - regardless of what kind of an antenna it is employed. (For openers I suggest you start here http://www.w2du.com/r2ch21.pdf ) Then, after getting a grasp on that aspect continue to learn how common mode current on the transmission line can effect the overall performance of an antenna's radiation pattern - especially with VHF & UHF antenna systems then you just might understand what people here are trying to tell you. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Others have measured this and reported it to you, but for some reason you chosen to discount anyone who can show that it disagrees with your "pet" theory. For me, I've place your theory along with the world is flat, the moon is made of green cheese, and Iraq has weapons of mass destruction . But even for a skeptic, I would thing that the thought of coiling up a few turns of coax costs very little, definitely won't hurt, and can only help. Would be sufficient. Danny, K6MHE I said I was done with this subject, But ........ I can't take it anymore. Again, the Arrow Antenna OSJ Antenna does NOT need a choke balun. By that I mean it will make no noticeable difference in performance of this particular antenna. (I am not lumping all VHF & UHF antennas together. I am ONLY talking about the OSJ). If you don't have a physical Arrow Antenna OSJ to test with and without a balun, you don't know what you are talking about. That goes for computer modeling also. You can't hook up a radio to computer model. This antenna works just fine the way it is. By the way Danny, what is the name of your Antenna Company ? 73 Al Lowe N0IMW Arrow Antenna Allen, My comments were directed to Ed not you, however, can you please explain to me what is the magical ingredient in your OSJ that makes it different than any other antenna known to man in that there will be no common mode current on a coax transmission line when directly connected to the antenna? Understand I am not saying your antenna doesn't work - never did say that. I will say that using a choke at the antenna's feed point will assure that the antenna will be operating at its best (maximum signal towards the horizon). By not using a choke can cause an increase to high angle radiation at the cost of reducing radiation toward the horizon due to common mode current on the transmission line - just like any other VHF antenna feed with coax. In other words the antenna is still radiating the same amount of power, however, much of the your signal is being wasted in the wrong direction (unless you are talking to airplanes). For the sake of me I can't fathom why you can not understand that. As for you question: I did not claim to own an antenna company. Is that germane to the subject of the thread? 73 Danny |
In article ,
Dan Richardson k6mheat wrote: Allen, My comments were directed to Ed not you, however, can you please explain to me what is the magical ingredient in your OSJ that makes it different than any other antenna known to man in that there will be no common mode current on a coax transmission line when directly connected to the antenna? May I chime in? Here's my best guess as to the situation with this antenna: - Like any other VHF antenna without an effective feedline- decoupling arrangement and isolation from the mast, it's possible for the feedline and/or mast to carry some amount of RF current. Quite simply, there's nothing stopping this from happening. - The RF impedance of the feedline shield and/or the mast will appear in parallel with the impedance of the longest (2-meter radiator) and shortest (440 matching arm) elements on the OSJ. - What this impedance will be, will be extremely installation- specific, and so will the currents carried on the feedline braid and/or mast. - If the length of these elements to the nearest ground is an odd multiple of a quarter-wavelength, the low-Z ground will transform back to a high-Z at the feedpoint, and little unwanted current will flow. If it's an even number of quarter-wavelengths, the impedance on the unwanted element will be quite a bit lower - the lower limit is probably the radiation resistance of a wire of that length. If it's a nonintegral multiple of a quarter wavelength, the impedance will be intermediate between these points and will be rather reactive. - If the mast is ungrounded at the bottom, the relationships in the previous paragraph will be reversed - high-Z for even number of quarter wavelengths, lower (set by radiation resistance) at an odd number of quarter-wavelengths, reactive in between. - Since the feedline and mast are likely to be longer than a metre, any radiation from them is likely to be have strong high-elevation- angle lobes. Power radiated in these lobes will be less "useful" in many applications, and since it takes away from the towards-the- horizon pattern of a theoretically-perfect halfwave radiator it will reduce the antenna's useful pattern gain by some amount. So far, I think this is all pretty standard per theory. Here's where I go out on a limb of speculation: - In a typical OSJ installation, the feedline and mast are relatively long, compared to the near-half-wavelength size of the radiator. - For this reason, if the feedline/mast length happens to be one with a low and non-reactive RF impedance, its impedance will be a good deal higher than that of the antenna itself due to the higher radiation resistance (e.g. 100-200 ohms). Only a relatively small fraction of the power at the feedpoint will flow into the braid or mast. As a result, the amount of power "robbed" from the primary radiator will be small, the high-angle lobes will be weak, and the reduction in the strength of the towards-the-horizon primary lobe will be minor. - If the feedline and/or mast happens to be of a length which results in a high impedance appearing at the feedpoint, then even less power will flow on these unwanted elements and the pattern disruption will be even less. If the above model and speculation are correct, then two things can probably be said: [1] In many installations - perhaps most - the OSJ probably works just fine without any sort of choking or decoupling arrangement (where I define "just fine" as "Adding a theoretically-perfect decoupling arrangement would not result in an improvement in pattern, ERP, receive sensitivity, etc. which the antenna's owner would notice or consider worth the trouble." [2] In some installations, under specific conditions (e.g. short 1/2-wavelength-long feedline) a choke might result in at least some useful (or at least measureable) improvement in towards- the-horizon pattern. I'll finish up by adding a personal observation. As Ed mentioned, the Arrow OSJ (and/or equivalent antennas made by a local amateur) are quite popular among members of our city's ARES group. I've measured a couple of them using an MFJ analyzer, and in my measurements I have *not* noticed the SWR / measured-impedance to change significantly when I touch or move the antenna feedline (even when it's a relatively short 6' piece of RJ58). This suggests to me that (in this case at least) there's not a lot of RF coming back down the outside of the feedline to the analyzer case, and that the near-50-ohm impedance presented by the radiator and matching stubs is the dominant "sink" for the RF current flow. Do I think the OSJ is perfect? No - no practical antenna is. If I were putting one up for a permanent installation, I'd probably insulate it from the mast, and loop the feedline coax into a choke balun and/or add a couple of ferrite beads, just because I'm picky and because the effort to do so is so small. I would not, however, count on noticing any practical difference in performance from doing so, and I wouldn't bother doing this in any sort of temporary or field installation (which is the purpose for which I keep a break-apart OSJ in my van). To that extent, I think that Al's statement that the OSJ doesn't need a choke, is a reasonably fair one. It's not a universal TRVTH but it's probably a fair, practical rule-of-thumb. -- 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! |
My comments were directed to Ed not you, however, can you please
explain to me what is the magical ingredient in your OSJ that makes it different than any other antenna known to man in that there will be no common mode current on a coax transmission line when directly connected to the antenna? I can't believe you are saying ALL antennas are exactly the same !!! Understand I am not saying your antenna doesn't work - never did say that. I will say that using a choke at the antenna's feed point will assure that the antenna will be operating at its best (maximum signal towards the horizon). By not using a choke can cause an increase to high angle radiation at the cost of reducing radiation toward the horizon due to common mode current on the transmission line - =A0just like any other VHF antenna feed with coax. There you said it again. In other words the antenna is still radiating the same amount of power, however, much of the your signal is being wasted in the wrong direction (unless you are talking to airplanes). For the sake of me I can't fathom why you can not understand that. No the antenna is NOT perfect. Adding a choke would not make it perfect. If it was perfect like you want, I might not be able to make contact with cross band repeater on a balloon at 60,000 feet 200 miles away. And still use a repeater 100 miles away, full quieting with 5 watts. Check the distance between Denver CO & Cheyenne WY. Your saying all antennas are the same is like saying all antennas with a gamma match have a skewed pattern.=20 73 Al Lowe N0IMW |
I've measured a
couple of them using an MFJ analyzer, and in my measurements I have *not* noticed the SWR / measured-impedance to change significantly when I touch or move the antenna feedline (even when it's a relatively short 6' piece of RJ58). =A0This suggests to me that (in this case at least) there's not a lot of RF coming back down the outside of the feedline to the analyzer case, and that the near-50-ohm impedance Sniped Funny how much the comments differ from some one who has a physical OSJ Antenna and those who just try and model it or or assume they know it won't work well. 73 Al Lowe N0IMW |
That's an excellent summary by Dave. However, I didn't see any mention
of common mode current due to mutual coupling between the feedline and the antenna. Even if you perfectly choke the common mode current at the feedpoint, considerable current can be induced onto the feedline. This won't happen with a symmetrical dipole if the feedline is oriented at right angles to the antenna. but where the antenna and feedline are collinear, as they are in a J-Pole or ground plane antenna, coupling can be substantial. The criterion for maximum current in that case is whether the decoupled section of the feedline is approximately resonant. For example, a quarter wave feedline grounded at the bottom and decoupled at the top (i.e., with a current balun - common mode choke - at the feedpoint) can have considerable current induced. It turns out that the conditions for maximum induced current can be opposite those for conducted current. For example, a half wavelength feedline that's not grounded at the bottom end won't have a great deal of conducted current. However, it can have quite a bit of induced current *if decoupled at the feedpoint*. If there's a good balun at the feedpoint, the isolated feedline becomes approximately self-resonant. Here's an example, for those who have EZNEC: Begin with example model VHFGP.EZ. First, in the main window, select Units, change to any units other than Wavelengths, and click Ok. Then select Units again, change back to Wavelengths, and click Ok. (This is necessary because of an EZNEC bug I discovered while preparing this. It affects only old files with Wavelength units, which include example files VHFGP and W8JK. When opened, these files will show the wire diameter units as being in Inches in the Units selection, but Wavelengths in the Wires Window. This bug will be fixed in the next update release, v. 4.0.17. In the meantime, you can re-save the files after changing the units and changing back, and they'll be ok from then on.) Add a wire with End 1 at 0, 0, 5 and End 2 at 0, 0, 4.5, 10 segments. Make the diameter 0.25 inch. This represents the outside of a feedline. Click the Currents button at the left of the main window and look at the current on the new wire, Wire 6. You should see that it's about 0.19 amp at End 1 (the top). (You'll see a different value if you've set a power level in the Options menu.) Now add a decent balun by adding a load with R = 1000 ohms to End 1 of Wire 6 (0% of the way from End 1). Click Currents again. Note that the current is now maximum at the middle of Wire 6, and it's more than twice what it was before -- about 0.42 amp. This is a situation that I'd frankly never considered before -- where a feedpoint balun can actually *increase* the common mode current! The current can, of course, be lowered to a small value by adding a second current balun (common mode choke) about a quarter wavelength down the wire (Wire 6, 50% from End 1). To stop the conducted current, you need a choke at the feedpoint or, alternatively, an even number of half wavelengths from it. To stop the induced current, you need a break up a resonant line by adding a choke about a quarter wavelength or an odd number of quarter wavelengths from an open end, or an even number of half wavelengths from a grounded end. Of course, you can alter the feedline length in such a way that both are minimized without needing a choke. Roy Lewallen, W7EL |
In article ,
Roy Lewallen wrote: This is a situation that I'd frankly never considered before -- where a feedpoint balun can actually *increase* the common mode current! The current can, of course, be lowered to a small value by adding a second current balun (common mode choke) about a quarter wavelength down the wire (Wire 6, 50% from End 1). To coin a phrase: "Fascinating!" Thanks for pointing this out, Roy. This gives an interesting twist to some advice I'd read several times... that to choke off feedline current one should install two chokes or ferrite beads, a quarter of a wavelength apart on the feedline. I had always assumed that this was simply a quickie way of making sure that a useful amount of choking reactance was sure to be installed fairly close to a current maximum, where it'd be most effective, and that if you knew where the current maximum actually was and put a choke there, you wouldn't really need to install the second choke. The fact that the conduction and induction currents behave differently would seem to rule that out - there really _is_ a good reason to have two chokes, to handle the two modes. Hmmm... slightly crazed idea... I wonder if there's a market for a coax with some amount of ferrite dust mixed into the PVC jacket when it's extruded, so as to create a self-choking distributed-inductance feedline. If the more rabid audiophiles can be convinced to spend thousands of dollars for a one-meter RCA-plug-tipped interconnection, maybe the excessively- well-to-do ham (there must be at least one) would pay ridiculous sums for a self-baluning RG-8? Might be a neat income opportunity, if one could sell it at high prices and still stand to look at ones face in the mirror the next morning (I couldn't, but I imagine there are people who could). -- 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! |
On 16 Jun 2005 15:14:13 -0700, "Al" wrote:
Your saying all antennas are the same is like saying all antennas with a gamma match have a skewed pattern. 73 Al Lowe N0IMW Damn it Allen, what I am saying is coax is coax and it will behave the same regardless of what antenna it is connected to. I feel you missing the whole point. I am not attacking you antenna. I just disagree with your advise on its installation. 73, Danny, K6MHE |
Hi Dan,
My, you are a bit on the arrogant and foul-mouthed side, aren't you! It would be tedious to try and dissect your attributions of positions that I did not take, so I'll skip that. I'll just point out that as an E.E. with three degrees from a top-5 engineering school, and a lifelong specialization in RF engineering, I don't need any patronizing lectures from you. "Physician," heal thyself... or at least try to understand the difference between theoretical niceties and practical effects. Reading Dave's posts might help. (He's much more patient with twits than I am, and explains things well.) BTW, I have nothing against coax "baluns," unless they become physically awkward, or noticeably increase cable loss. Ed "Dan Richardson arrl net" k6mheatdot wrote in message ... On Mon, 13 Jun 2005 22:54:01 GMT, "Old Ed" wrote: Don't let the nay-sayers in this NG bother you, and don't waste your time arguing with them. Some of them can't stand the thought that any antenna which differs from their personal pet(s) might be good. Others can't grasp the idea that when model predictions and actual results differ, it's the results that count. Spoken like a true naif. I suggest that you would take the time to learn what causes common mode current to be present on coax transmission line - regardless of what kind of an antenna it is employed. (For openers I suggest you start here http://www.w2du.com/r2ch21.pdf ) Then, after getting a grasp on that aspect continue to learn how common mode current on the transmission line can effect the overall performance of an antenna's radiation pattern - especially with VHF & UHF antenna systems then you just might understand what people here are trying to tell you. However, I doubt that you would do that as it would appear you've made up your mind and don't want to be confused with known facts. Still others can't seem to understand that effects too small to measure usually do not matter in the real world. Others have measured this and reported it to you, but for some reason you chosen to discount anyone who can show that it disagrees with your "pet" theory. For me, I've place your theory along with the world is flat, the moon is made of green cheese, and Iraq has weapons of mass destruction . But even for a skeptic, I would thing that the thought of coiling up a few turns of coax costs very little, definitely won't hurt, and can only help. Would be sufficient. Danny, K6MHE |
On 16 Jun 2005 10:29:02 -0700, "Al" wrote:
[snip I said I was done with this subject, But ........ I can't take it anymore. I thought I was too but I can't take it anymore either. Again, the Arrow Antenna OSJ Antenna does NOT need a choke balun. No antenna *needs* a balun. Most will deliver more predictable performance when they incorporate one however. Your's is not an exception, in fact, it's a glaring example of where one *should be* used. Furthermore, a non-conductive support should be used as well. A balun on a piece of coax that is in parallel with a conductive mast is worthless. If these things aren't used, then you are selling only part of the antenna system; the upper part...with the user is supplying the lower part. I suppose you could argue that the part you sell, when mounted directly on an infinite ground plane, doesn't need a balun, but I don't see that limitation spelled out in your literature. By that I mean it will make no noticeable difference in performance of this particular antenna. (I am not lumping all VHF & UHF antennas together. I am ONLY talking about the OSJ). When "performance" is measured by whether or not you can break the squelch of the local repeater, then you are correct, it makes no difference as long as the squelch is broken. If you don't have a physical Arrow Antenna OSJ to test with and without a balun, you don't know what you are talking about. That goes for computer modeling also. You can't hook up a radio to computer model. Uh huh. So since you don't trust modeling, I guess you have a high class antenna range that you use to design your antennas. That must be how you substantiate such claims as, "This antenna has a good combination of gain, front/back & bandwidth" and where you prove that the pattern of your J-pole is unaffected by the supporting mast and/or transmission line. Whoops---wait a minute---right he http://arrowantennas.com/inst/ijpole.html I see 3D radiation plots made from a *COMPUTER MODEL*. Plus I see SWR plots that (convienently) are 1.0:1 over the whole 2-meter band. That is amazing. My dummy load isn't that good. Look. I'm sure you're a very nice guy and we would probably enjoy having a few beers together. I've already commented on your ingenuity in designing and constructing your production machinery and your products seem to be very well made. But your performance claims are over the top and while I know that almost everybody in the ham antenna business is prone to rub a little snake oil on their ads, it doesn't mean that I'm going to agree with it or refrain from skewering those who do it. |
On Fri, 17 Jun 2005 14:24:20 GMT, "Old Ed"
wrote: Hi Dan, My, you are a bit on the arrogant and foul-mouthed side, aren't you! Foul-mouthed? |
Damn it Allen, what I am saying is coax is coax and it will behave the
same regardless of what antenna it is connected to. I feel you missing the whole point. I am not attacking you antenna. I just disagree with your advise on its installation. Hello, Danny, K6MHE I am not missing the point, I just have a different point I have to deal with. Check the last few posts, especially the one from Roy. Can you imagine trying to explain that to some one that don't understand why the coax he took off an old computer network don't work with his 2 meter radio. You have to realize, a lot of times I am dealing with hams that just got their license last week. One's that have trouble putting a connector on coax. A lot of the time they don't even have an SWR meter, or they are trying to use one from their old CB. The ham buying a $39. antenna that don't have to be tuned or adjusted, is at a different knowledge level than a ham that can set up an EME station. I am not an antenna guru, I know less about coax & baluns than I know. That's why I have been reading this newsgroup for the last 10 years. Why heck, I cant even spel. The OSJ is a good entry level to antennas. It get's them on the air, so they can learn more. I think I am doing a good service. At least I feel good reading the e-mails I get almost every day from people using my antennas. 73 Al Lowe N0IMW |
Al, I have a fair idea of antennas and baluns and how the electrons and
homotrons bounce around these magical devices.. Your antenna works well for it's intended purpose. I have two of your J-poles, one on the house and one on the roof of the car. (Takes 6 large rubber bands to remove the mechanical resonance at 70 MPH) They connect me with the local repeaters, withstand hurricane winds, and are trouble free. At $39.00 a bargain by any description. Many here enjoy picking fly crap out of pepper, that is their enjoyment of ham radio. No different than contester, DX hounds etc. I enjoy the discussions of folks that will spend days bloviating on the state of an electron named George at an SWR of 1.000000001:1. These folks have caused me to think, as well as learn, just to keep up with the pin dancing. That's a good thing While some can appear officious and supercillious in the process, once you get beyond that, pearls of wisdom do appear. Continue making a great antenna, those that desire to achieve antenna nirvana may spend time with the tweezers removing the afore mentioned flyspecks. "Iligitimus non carborundum" "Al" wrote in message oups.com... Damn it Allen, what I am saying is coax is coax and it will behave the same regardless of what antenna it is connected to. I feel you missing the whole point. I am not attacking you antenna. I just disagree with your advise on its installation. Hello, Danny, K6MHE I am not missing the point, I just have a different point I have to deal with. Check the last few posts, especially the one from Roy. Can you imagine trying to explain that to some one that don't understand why the coax he took off an old computer network don't work with his 2 meter radio. You have to realize, a lot of times I am dealing with hams that just got their license last week. One's that have trouble putting a connector on coax. A lot of the time they don't even have an SWR meter, or they are trying to use one from their old CB. The ham buying a $39. antenna that don't have to be tuned or adjusted, is at a different knowledge level than a ham that can set up an EME station. I am not an antenna guru, I know less about coax & baluns than I know. That's why I have been reading this newsgroup for the last 10 years. Why heck, I cant even spel. The OSJ is a good entry level to antennas. It get's them on the air, so they can learn more. I think I am doing a good service. At least I feel good reading the e-mails I get almost every day from people using my antennas. 73 Al Lowe N0IMW |
On 17 Jun 2005 08:28:45 -0700, "Al" wrote:
The OSJ is a good entry level to antennas. It get's them on the air, so they can learn more. I agree. very 73, Danny, K6MHE |
On Fri, 17 Jun 2005 12:36:14 -0400, "Fred W4JLE"
wrote: Many here enjoy picking fly crap out of pepper, that is their enjoyment of ham radio. Hi Fred, I've seen you use this platitude more than once. As much truth as it may offer, it necessarily presumes there is someone energetically putting fly crap into the pepper. I won't tarry to imagine how that is done, however. 73's Richard Clark, KB7QHC |
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