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Log-Periodic Antenna Design
christofire wrote:
"Rich Grise" wrote in message ... My current UHF antenna is a 14" Radio Shack clip lead clipped from the center of my coax to the venetian blind. I have to hand-adjust it for the channel, weather conditions, phase of the moon, etc. I can do this because I can _see_ an indication of signal strength. Well, with this new Fascist "No More Free TV" crap, I'm gonna need a real UHF antenna. My budget is exceedingly limited, but I have a supply of materials (GTAW filler rod, with some coppery-colored coating, so it solders like a dream, and is as stiff as piano wire) to build an antenna with. But I've been searching the web for some weeks now, and I can't seem to find any kind of formula, except there was this program I downloaded - LPDA.EXE, which runs on DOS. Unfortunately, it's in Russian or Polish or Uzbekistani - one of those East Yurp languages. Here's a screen snap: http://mysite.verizon.net/richgrise/...rog-Output.gif Which I went through pretty much by-guess-and-by-gosh - can anybody read that stuff? There are a lot of factors I don't know about, like "Tau", and all of the specific designs on the web are flat - something is telling me I want one of those pyramid-shaped ones, but I really don't know the difference (between that and flat) - it's probably something to do with bandwidth or F/B ratio or whatever. My local library has no ARRL Antenna Book (!), and did I mention I have a seriously limited budget? So, how do I pursue this? It'd be nice to have a program that will calculate the whole thing for me, but am I dreaming? If I want to send myself to Log-Periodic School, where should I start? Or, does anyone have a UHF-TV log-periodic design that they'd share? :-) Thanks, Rich You probably don't need a program, just a decent text book that covers the topic adequately, which, undoubtedly is what the program writers worked from, and they might not have got it right! 'Antennas' by John Kraus contains enough detail to make a start and it's probably more general than someone's program which might involve specific choices of some parameter values. So my recommendation would be to find a technical library that offers access to non-members and send yourself to Log-Periodic School as you put it. The IET library in London does this, for free. Do you have an equivalent institution (e.g. IEEE), or a local university that covers electronic engineering? You might be surprised how much access you can gain to libraries to which you have contributed through taxes, or which need to maintain an 'altruistic' public appearance. Orfanidis's book on electromagnetic waves and antennas is online, and covers LPDAs.. Kraus is better, but you'll have to fork out at least $20+shipping for a used copy. Kraus *is* my recommendation if you have to have a single antenna book, though. |
Log-Periodic Antenna Design
"Rich Grise" wrote in message
... I was doing a thought experiment with this and when it's completely "flattened out", (180 degrees between the booms), it looks like a drum roll please Bow Tie! I think a bow tie's design is actually motivated more by one of the "standard" ultra-wideband antenna designs, that of a pair of opposing cones touching each other at their narrow ends, being translated down into 2D. |
Log-Periodic Antenna Design
Jim Lux wrote:
Kraus is better, but you'll have to fork out at least $20+shipping for a used copy. Kraus *is* my recommendation if you have to have a single antenna book, though. Here's a new international 3rd edition available for less than $10 plus shipping. http://www.abebooks.com/servlet/Sear...tennas&x=0&y=0 -- 73, Cecil http://www.w5dxp.com |
Log-Periodic Antenna Design
Rich Grise wrote:
... Hey, "John Smith", why don't you go outside and play hide-and-go-****-yourself? Cheers! Rich LOL ... Darn, you just can't get decent psychiatric help with your food stamps, can you? :-( Regards, JS |
Log-Periodic Antenna Design
GregS wrote:
Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. greg That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? Roy Lewallen, W7EL |
Log-Periodic Antenna Design
Rich Grise wrote:
On Wed, 19 Nov 2008 22:53:28 -0800, Richard Clark wrote: . . . 73's "Best Regardses"? ;-) No, that's "Best Regards's". It's the possessive, not plural, form of "Best Regards". I think the grammar is part of the same dialect as the verb "destinate" (as in "I've just destinated"), but you'd have to ask Richard about that -- he's the one with the English Lit degree. Roy Lewallen, W7EL |
Log-Periodic Antenna Design
"Rich Grise" wrote in message ... My current UHF antenna is a 14" Radio Shack clip lead clipped from the center of my coax to the venetian blind. I have to hand-adjust it for the channel, weather conditions, phase of the moon, etc. I can do this because I can _see_ an indication of signal strength. Well, with this new Fascist "No More Free TV" crap, I'm gonna need a real UHF antenna. My budget is exceedingly limited, but I have a supply of materials (GTAW filler rod, with some coppery-colored coating, so it solders like a dream, and is as stiff as piano wire) to build an antenna with. It may not take too much antenna. I picked up one of the converter boxes and hooked it to a 432 mhz beam at 70 feet and got 21 stations on the auto tune. Then to a 9 element M2 2 meter bem and it picked up 29 stations. This was at the end of about 130 feet of low loss rg-8 size coax and then 25 feet of rg-6. Several of the stations were the same transmitter,but differant chanels on the TV. |
Log-Periodic Antenna Design
"Joel Koltner" wrote in message ... I think a bow tie's design is actually motivated more by one of the "standard" ultra-wideband antenna designs, that of a pair of opposing cones touching each other at their narrow ends, being translated down into 2D. Standard, indeed; this antenna is known as a biconical. It has excellent wideband response making it ideal for EMC testing. Most good antenna texts such as that by Krauss give a detailed analysis of the biconical antenna. I see no relationship between its design and a fractal design other than both are wide bandwidth antennas. The bowtie antenna which Rich and others have mentioned is a "flattened" form of the biconical. If the bowtie is bent along its major axis, it makes an excellent wideband driven element for a corner reflector antenna. 73, Barry WA4VZQ |
Log-Periodic Antenna Design
Thanks for the details, Barry... tell me though, then, is a discone just a
biconical with a ground plane used to create the (image of the) missing cone? |
Log-Periodic Antenna Design
"Joel Koltner" wrote in message ... Thanks for the details, Barry... tell me though, then, is a discone just a biconical with a ground plane used to create the (image of the) missing cone? Yes. It will have less gain than a biconical and the bandwidth is slightly more restrictive too. But it is much easier to construct! 73, Barry WA4VZQ |
Log-Periodic Antenna Design
On Thu, 20 Nov 2008 15:35:53 -0800, Roy Lewallen wrote:
Rich Grise wrote: On Wed, 19 Nov 2008 22:53:28 -0800, Richard Clark wrote: . . . 73's "Best Regardses"? ;-) No, that's "Best Regards's". It's the possessive, not plural, form of "Best Regards". I think the grammar is part of the same dialect as the verb "destinate" (as in "I've just destinated"), but you'd have to ask Richard about that -- he's the one with the English Lit degree. I read it in a QST or so back in the 1960's. :-) Thanks! Rich ex-WN0GJS |
Log-Periodic Antenna Design
On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote:
GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...earch&aq=f&oq= Hope This Helps! Rich |
Log-Periodic Antenna Design
Rich Grise wrote: On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote: GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...earch&aq=f&oq= Hope This Helps! Rich Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? Roy Lewallen, W7EL |
Log-Periodic Antenna Design
On Fri, 21 Nov 2008 00:51:28 GMT, Rich Grise wrote:
On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote: GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...earch&aq=f&oq= Hope This Helps! Rich Hi Rich, Tacking the new-age term of "fractal" to antenna does not automatically bring: 1. Widebandedness; 2. Gain; 3. Small size. The link above fairly confirms it in the fog of offering. I could expand upon this - but the interest of those who become suddenly engaged with the topic rarely translates into a meaningful discussion, and never leads to an actual construction. 73's Richard Clark, KB7QHC |
Log-Periodic Antenna Design
"Ralph Mowery" wrote in message ... snip It may not take too much antenna. It doesn't. I have two converter boxes, one Magnavox, one Zenith. I just now tried my local stations with them using a straight 24-inch alligator clip lead as the antenna. Location is a residential garage in the San Diego suburbs. Stucco walls, metal garage door closed, overhead fluorescent lights on. Transmitters in three different locations. All the UHF locals came in, 10 transmitters with about twenty total programs. The one low-power VHF did not. Looping the clip lead back and clipping the end to the F-connector produced about the same results. (Lost one TJ station.) When I "upgraded" to a POS 2-bay bowtie in the rafters (about 8 feet up), all eleven locals came in, plus KCBS from LA . On the Zenith box, arguably a better unit, I got two more LA channels, although one of them had some intermittent freezing and tiling. If even poor antennas work well, why all the whining? "Sal" (KD6VKW) |
Log-Periodic Antenna Design
Roy Lewallen wrote:
Rich Grise wrote: On Wed, 19 Nov 2008 22:53:28 -0800, Richard Clark wrote: . . . 73's "Best Regardses"? ;-) No, that's "Best Regards's". It's the possessive, not plural, form of "Best Regards". I think the grammar is part of the same dialect as the verb "destinate" (as in "I've just destinated"), but you'd have to ask Richard about that -- he's the one with the English Lit degree. My Webster's unabridged dictionary gives the following examples of the correct way to pluralize numbers. "figure 8's", "the 1890's", "the 20's" 73 is a number that stands for "Best Regards" 73's would be "Lots of Best Regards". -- 73, Cecil http://www.w5dxp.com |
Log-Periodic Antenna Design
Roy Lewallen wrote:
Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? http://ieeexplore.ieee.org/Xplore/lo...number=1610336 If you are a member of IEEE, you can access this paper: Multiband behavior of wideband Sierpinski fractal bow-tie antenna Yamini, A.H.; Soleimani, M. Microwave Conference, 2005 European Volume 3, Issue , 4-6 Oct. 2005 Page(s): 4 pp. - Digital Object Identifier 10.1109/EUMC.2005.1610336 -- 73, Cecil http://www.w5dxp.com, IEEE |
Log-Periodic Antenna Design
Sal M. Onella wrote:
If even poor antennas work well, why all the whining? I've not had any problems with the UHF circular loop that comes with standard rabbit ears. The only problem I've had is with VHF channels on the dipole. I need a weatherproof version of my RS rabbit ears. Unfortunately, ABC is Channel 7 here in Tyler, TX. -- 73, Cecil http://www.w5dxp.com |
Log-Periodic Antenna Design
Rich Grise wrote:
On Thu, 20 Nov 2008 13:50:57 +0000, Dave wrote: Log periodics are not necessary for sub-octave operation. http://www.youtube.com/watch?v=EWQhlmJTMzw Dude! Awesome! And this one doesn't even have a reflector!. I wonder how far I should hang it in front of the venetian blind. ;-) Thanks! Rich I don't have time to search for it, but there's also a dual quad UHF TV antenna that's easy to build with the same kind of materials. I prefer steel tie wire to coat hangers because it's easier to work with. |
Log-Periodic Antenna Design
On Nov 21, 7:36�am, Cecil Moore wrote:
Sal M. Onella wrote: If even poor antennas work well, why all the whining? I've not had any problems with the UHF circular loop that comes with standard rabbit ears. The only problem I've had is with VHF channels on the dipole. I need a weatherproof version of my RS rabbit ears. Unfortunately, ABC is Channel 7 here in Tyler, TX. -- 73, Cecil �http://www.w5dxp.com Now that the FCC has given a green light to whitespace device deployments (particularly those that rely solely on spectrum-sensing technology), you may find you need a better antenna than a simple loop, bowtie or coat hanger. For those of you who are not following the issue, a quote in this week's TV Technology pretty much sums it up: "MSTV (Maximum Service Television) told the Commission Oct 31 that the least the FCC could do is subject the devices to rigorous testing beforehand and ensure fair and reliable tests to prevent interference to DTV. In a filing, MSTV also attacked the FCC proposal that a device should be able to detect signals as low as -114 dBm, a level MSTV equated with setting a smoke detector to only be able to detect a raging fire." Whitespace devices will also cause great harm to wireless microphones, particularly older models. -mpm |
Log-Periodic Antenna Design
Cecil Moore wrote:
... My Webster's unabridged dictionary gives the following examples of the correct way to pluralize numbers. "figure 8's", "the 1890's", "the 20's" 73 is a number that stands for "Best Regards" 73's would be "Lots of Best Regards". A friend of mine is a dispatcher for police/fire/ambulance/etc., in my area. Her 10 code often requires her to use the "10-73" from this ten code--which is a "smoke report." So, thanks for clarifying this for me. I simply took the 73's on many of the posts sigs as a sign they were "blowing smoke" (actually, "Lots of smoke!" :-) ), and giving me fair warning! straight-face Regards, JS |
Log-Periodic Antenna Design
In article tonline, Roy Lewallen wrote:
Rich Grise wrote: On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote: GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...oogle+ Search &aq=f&oq= Hope This Helps! Rich Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? Roy Lewallen, W7EL I don't have data. I think the home made TV antenna in the video, is very much like a bow tie, and could have better bandwidth by making the elements different lengths. The gain factor is going to be narrow band since the feed length is constant. I would have also used 12ga copperweld or solid copper. You can also get closer to fractal by using many more different sized elements. greg |
Log-Periodic Antenna Design
"NoSPAM" wrote in message ... "Joel Koltner" wrote in message ... Thanks for the details, Barry... tell me though, then, is a discone just a biconical with a ground plane used to create the (image of the) missing cone? Yes. It will have less gain than a biconical and the bandwidth is slightly more restrictive too. But it is much easier to construct! 73, Barry WA4VZQ All else being equal, a lossless 'ground plane' type antenna, be it a monopole developed from a dipole or a discone developed from a biconical dipole, over an infinite ground plane should exhibit 3 dB _more_ gain than the symmetrical 'parent' form of antenna. This is because its radiation pattern is limited to half the solid angle of the parent (e.g. only the space above the ground plane). Then for a given number of watts fed into the antenna, the power-flux density must be greater in the region where it can radiate. In practice, the ground plane isn't infinite so there is some 'undercutting' of the vertical radiation pattern, but the gain should still be somewhat greater. The apex angle of the cone in a discone can be chosen to yield 50 ohms terminal resistance over part of its usable bandwidth, and that angle is different from the apex angle(s) needed in a biconical dipole for the same impedance. The usable bandwidth is always limited by the limited flare-length of the cone(s) and usually also by the accuracy of the apex or apices where termination is made. Chris |
Log-Periodic Antenna Design
If you are a member of IEEE, you can access this paper:
Multiband behavior of wideband Sierpinski fractal bow-tie antenna And if you aren't a member, you aren't in on the joke? With all the added capacitance to the elements, I have little doubt that there would be lots of resonance's, and it would be cool to choose the geometry to bring about the proper feed point impedances, but these things can never be gainful with all the losses introduced. Neat idea for specific applications like little pocket toys, but certainly not the answer to everything. I wonder how the Limo's will deal with DTV in motion. |
Log-Periodic Antenna Design
I don't have data. I think the home made TV antenna in the video, is very
much like a bow tie, Comparable to a 4 bay bowtie. Maybe 6db gain. Brazing rod would be a little lighter and wouldn't rust. Would work much with a reflecting plane and above the house clutter. Twin lead could make a comeback since there won't be such a worry about the low band interference issue. Actually much less loss than coax. I may yet change over to 300 ohm window line on my bigazz deep fringe at 40ft and switch it to the ham shack for 6/2m SSB work and DTV DX. TV DX won't be dead, you will just have to know where to find it |
Log-Periodic Antenna Design
"mpm" wrote in message
... "Whitespace devices will also cause great harm to wireless microphones, particularly older models." Isn't the estimate that something like 90% of all wireless mics are being used by folks who technically never had the authorization to use the spectrum (...that is used...) is the first place? Something like how only radio and TV stations had the authority to use the standard wireless mic frequencies, but these days anyone doing professional sound for theater, sporting events, etc. is also using those same frequencies? |
Log-Periodic Antenna Design
On Fri, 21 Nov 2008 16:26:27 -0000, "christofire"
wrote: The apex angle of the cone in a discone can be chosen to yield 50 ohms terminal resistance over part of its usable bandwidth, and that angle is different from the apex angle(s) needed in a biconical dipole for the same impedance. The usable bandwidth is always limited by the limited flare-length of the cone(s) and usually also by the accuracy of the apex or apices where termination is made. Hi Chris, This needs heavy qualification, and probably too much such that a graphical treatment would outweigh the words for contribution: http://www.qsl.net/kb7qhc/antenna/Discone/discone.htm 73's Richard Clark, KB7QHC |
Log-Periodic Antenna Design
Twin lead could make a comeback since there won't be such a worry about the
low band interference issue. Actually much less loss than coax. Maybe... when it's new, of the right type (e.g. tubular), clean, dry, and carefully installed. My understanding is that the performance of 300-ohm twinlead installations tends to deteriorate significantly after a few years (sunlight and ozone attacks the twinlead, and dirt and pollution builds up) and during wet weather. -- Dave Platt AE6EO Friends of 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! |
Log-Periodic Antenna Design
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Log-Periodic Antenna Design
On Thu, 20 Nov 2008 16:58:46 -0800, Roy Lewallen wrote:
Rich Grise wrote: On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote: GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...earch&aq=f&oq= Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? The only "evidence" I have is a "testimonial" by the guy who invented it, on some PBS show. And they claimed that that's how they pack so much antenna into a box the size of your thumb. ;-) And, having a passing familiarity with fractals, it just sounds eminently plausible to me. :-) Cheers! Rich |
Log-Periodic Antenna Design
On Nov 21, 5:53*pm, Rich Grise wrote:
On Thu, 20 Nov 2008 16:58:46 -0800, Roy Lewallen wrote: Rich Grise wrote: On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote: GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...s%22&btnG=Goog... Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? The only "evidence" I have is a "testimonial" by the guy who invented it, on some PBS show. And they claimed that that's how they pack so much antenna into a box the size of your thumb. ;-) And, having a passing familiarity with fractals, it just sounds eminently plausible to me. :-) Cheers! Rich Their advertising budget suggest that they are getting sales and they do radiate to the satisfaction of their users They don't have lumped loads so where ';s the beef? Art |
Log-Periodic Antenna Design
On Fri, 21 Nov 2008 06:36:32 -0600, Cecil Moore wrote:
Sal M. Onella wrote: If even poor antennas work well, why all the whining? I've not had any problems with the UHF circular loop that comes with standard rabbit ears. The only problem I've had is with VHF channels on the dipole. I need a weatherproof version of my RS rabbit ears. Unfortunately, ABC is Channel 7 here in Tyler, TX. Where I'm sitting here in Whittier, KABC 7 is so strong I can get it without even a cable plugged in! It's 50, 56, and 58 I worry about; 2-13 and 28 are covered; I'm looking forward to seeing if my new bowtie (from that youtube video, but with ER708-2 x 1/16 filler rod) will pick up PAX on 30. They have some nice oldies sometimes. (I also have some of the ER708-2 in 0.045".) I'm gonna solder it together and hold it to the board with brass thumb- tacks. ;-) Just for reference: http://www.youtube.com/watch?v=EWQhlmJTMzw Cheers! Rich |
Log-Periodic Antenna Design
christofire wrote:
All else being equal, a lossless 'ground plane' type antenna, be it a monopole developed from a dipole or a discone developed from a biconical dipole, over an infinite ground plane should exhibit 3 dB _more_ gain than the symmetrical 'parent' form of antenna. This is because its radiation pattern is limited to half the solid angle of the parent (e.g. only the space above the ground plane). Then for a given number of watts fed into the antenna, the power-flux density must be greater in the region where it can radiate. In practice, the ground plane isn't infinite so there is some 'undercutting' of the vertical radiation pattern, but the gain should still be somewhat greater. . . . This is entirely a fictional scenario, although it's the one used by virtually all the currently available modeling programs. In those programs you can choose "free space" or "ground plane", where the infinite "ground plane" restricts the field, as Chris says, to a single hemisphere while "free space" allows radiation in both hemispheres. In real life, you can't have either one, except that outer space would be a reasonable approximation of "free space". The only thing that matters is whether the field reflects from a large surface like the Earth on its way to the receiver. If it does, you potentially pick up field strength from reinforcement of the direct and reflected rays -- but of course you can also lose field strength if the two rays cancel rather than reinforcing. This is another way of describing the same phenomenon of increased gain due to a ground plane. Even if you put an antenna hundreds of wavelengths high, some of the signal will reflect from the ground -- it's not truly in "free space". It doesn't matter whether your antenna is a "ground plane" or a dipole -- if a reflection occurs between the transmitter and receiver, you potentially get that extra gain; if it doesn't, you don't. Roy Lewallen, W7EL |
Log-Periodic Antenna Design
On Nov 21, 7:04�pm, Art Unwin wrote:
On Nov 21, 5:53�pm, Rich Grise wrote: On Thu, 20 Nov 2008 16:58:46 -0800, Roy Lewallen wrote: Rich Grise wrote: On Thu, 20 Nov 2008 15:30:26 -0800, Roy Lewallen wrote: GregS wrote: Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band. It could be improved by making it a full fractal. That's interesting. In what way(s) is it improved by making it fractal? How much is the improvement? Can you point me to a reference about this which gives some quantitative data? http://www.google.com/search?hl=en&q...s%22&btnG=Goog... Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? The only "evidence" I have is a "testimonial" by the guy who invented it, on some PBS show. And they claimed that that's how they pack so much antenna into a box the size of your thumb. ;-) And, having a passing familiarity with fractals, it just sounds eminently plausible to me. :-) Cheers! Rich Their advertising budget suggest that they are getting sales and they do radiate to the satisfaction of their users �They don't have lumped loads so where ';s the beef? Art- Hide quoted text - - Show quoted text - It's a folded, folded, folded, folded, folded,... n(folded) unipole antenna!! ;-) |
Log-Periodic Antenna Design
On Nov 21, 7:04�pm, Rich Grise wrote:
Where I'm sitting here in Whittier, KABC 7 is so strong I can get it without even a cable plugged in! Decent power, line of sight (18.2 miles @ 172.2 deg true) will do that. Check your email.... -mpm |
Log-Periodic Antenna Design
Art Unwin wrote:
... Their advertising budget suggest that they are getting sales and they do radiate to the satisfaction of their users They don't have lumped loads so where ';s the beef? Art Art: I am ready to bend over backwards, until I can say different ... However, how much you wanna' pay me for one of these? --- | | -- telescoping whip | | |--------------------- --- / |-------------- coax \ |_______________ -- / ----- 50 ohm, five-watt or better non-inductive \ | / | | | ----- --- --- - -- ground - Lifetime antenna, virtually perfect SWR, no moving parts, guaranteed a lifetime, etc., etc. AND! I bet I can find some to give testimonials to it being an "excellent antenna." You know the game ... idiots are easily taken advantage of ... :-( BUT-EVIL-GRIN .... come on, argue something real ... Regards, JS |
Log-Periodic Antenna Design
"JB" wrote in message ... I wonder how the Limo's will deal with DTV in motion. Ahah! Presently they don't. A big issue for opponents of 8VSB modulation was poor performance in mobile/handheld (M/H) applications. Straight 8VSB does not handle "dynamic multipath" well. However ... Development of the ATSC-M/H Standard for mobile and handheld applications is moving forward at a rapid pace. A critical element of that effort is the Independent Demonstration of Viability (IDOV). The goal of IDOV is to ensure that the technical proposals under consideration can meet the goal of enabling mobile and handheld services in early 2009. per http://www.atsc.org/communications/n...r_standard.pdf - I read some news accounts of supposed successful tests (the "IDOV" ?) this past spring. We'll see. BTW, alt.video.digital-tv newsgroup is doing a good job with the TV transition. Also, http://www.avsforum.com/ has news, like http://www.avsforum.com/avs-vb/showthread.php?t=1078353 |
FCC TV Band Devices
Joel Koltner wrote:
"mpm" wrote in message ... "Whitespace devices will also cause great harm to wireless microphones, particularly older models." Isn't the estimate that something like 90% of all wireless mics are being used by folks who technically never had the authorization to use the spectrum (...that is used...) is the first place? Something like how only radio and TV stations had the authority to use the standard wireless mic frequencies, but these days anyone doing professional sound for theater, sporting events, etc. is also using those same frequencies? The FCC and the TV broadcasters looked the other way because there is no evidence that such activity has ever caused any interference. I can get 6 microphones to work in an occupied analog TV channel and neither notices the other. The TV Band Devices the FCC has recently begun the process of authorizing are way more damaging than a 50 mW 65 kHz deviation FM signal. Luckily, these devices will not be allowed anywhere near where I work. The FCC has banned them from the 13 biggest cities, and from within a kilometer of a venue or stadium using wireless microphones. The proposed rules do not require a Part 74 license for these protections. |
Log-Periodic Antenna Design
Rich Grise wrote:
On Fri, 21 Nov 2008 06:36:32 -0600, Cecil Moore wrote: Sal M. Onella wrote: If even poor antennas work well, why all the whining? I've not had any problems with the UHF circular loop that comes with standard rabbit ears. The only problem I've had is with VHF channels on the dipole. I need a weatherproof version of my RS rabbit ears. Unfortunately, ABC is Channel 7 here in Tyler, TX. Where I'm sitting here in Whittier, KABC 7 is so strong I can get it without even a cable plugged in! It's 50, 56, and 58 I worry about; 2-13 and 28 are covered; I'm looking forward to seeing if my new bowtie (from that youtube video, but with ER708-2 x 1/16 filler rod) will pick up PAX on 30. They have some nice oldies sometimes. (I also have some of the ER708-2 in 0.045".) I'm gonna solder it together and hold it to the board with brass thumb- tacks. ;-) Just for reference: http://www.youtube.com/watch?v=EWQhlmJTMzw Cheers! Rich Ion TV 30 is in Claremont and has a 3.8 Megawatt Signal (elliptically polarized no less). It should give you a tan in Whittier. |
Log-Periodic Antenna Design
Cecil Moore wrote:
Roy Lewallen wrote: Sorry, it doesn't. Among the claims, trolls for investors, and testimonials, where is the quantitative data showing that a fractal antenna is in any way better than a bow tie, in what ways, and how much? In other words, exactly where is the evidence on which you based your statement? http://ieeexplore.ieee.org/Xplore/lo...number=1610336 If you are a member of IEEE, you can access this paper: Multiband behavior of wideband Sierpinski fractal bow-tie antenna Yamini, A.H.; Soleimani, M. Microwave Conference, 2005 European Volume 3, Issue , 4-6 Oct. 2005 Page(s): 4 pp. - Digital Object Identifier 10.1109/EUMC.2005.1610336 interesting paper.. The big benefit (from a cursory reading).. is that you have a more consistent antenna pattern over the frequency range, which the vanilla bowtie does not. And a somewhat wider match bandwidth. (mostly extending it to higher frequencies) Nothing magic, though. |
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