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The bottomline is that you spent a lot of time and effort to refute a statement that nobody made. |
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http://www.tvfool.com/?option=com_wr...67d940ad1928dc as well as a few other UHF stations. Bottom line is still -- My antenna works, and the better of the 2 recommended by Dave didn't. And please understand me. I am not criticizing Dave's work, suggestiions or understanding, only try to educate myself on why an antenna works in application, but seems to be no longer feasable. Dave's first quote was: "There was a long thread on fractal antenna designs here at digitalhome.ca. That it hasn't been posted to for a while suggests that community has moved on to other designs." Dave's other quote was: "The modeling of the Ruckman fractal documented in that thread showed that it did not perform any better over the VHF and UHF bands than other designs. For hi-VHF, the gain is around 2 or 3 dB, which is good enough in your situation for reliable lock, but just barely. That's why the coffee grinder did in the VHF station." Maybe I was a bit "snippy" on one of my previous posts, and if I didn't apologize to satisfaction, please accept my sincere apology now. But please don't insult my intelligence by assuming what channels are in my area by looking at Mark's map and not mine. May I also suggest someone in the higher technical level actually build a version of my current antenna, http://www.leoda.us/Fractal%20antenn...20drawing.html and perhaps even model it, and explain to me why I get better reception, and can receive other stations a commercially, and technically accepted antenna couldn't. Also note that my current DIY is not using a reflector, and is not mounted on a PVC frame. Its simply held in place with the same brads I used to bend the wire. By technical standards, I probably broke every rule regarding impedance by having it mounted directly on foam board, and leaving the wire brads still connected to the elements. But it works! This antenna is not my design, and I'm also not trying to sell a version of this, only sharing my experience on using a DIY before spending $$$ on something else. Referring back to Mark's original post, he was looking for "value". In my opinion, building an antenna for less that $15 vs. $50 - $150, and the possibility of many trips to try other antennas, leans closer to value than debating VSWR, Gain or loss of gain, or other technical aspects of a receiving antenna. Again, my opinion. Unless Mark lives in a basement apartment, or doesn't have access to a suitable location, and given his distance from the transmitters, the same fractal design I'm using may or may not work. But, if he can bend wire and turn a screwdriver, the fractal antenna just might work for him too. Apparently, you picked up the thread in the middle, and unfortunately didn't get the whole story. |
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Dave Loudin's comments in post 7 & 8 of this thread speak to that. In particular, the extreme power level of the KAME signal is very likely causing your tuner to overload. An antenna with net gain in the UHF band is going to make overload still more likely. Your situation is not typical, but I'm quite happy that you've found an inexpensive solution that apparently attenuates the powerful UHF signal while receiving sufficient signal from weaker UHF and VHF stations. As long as the discussion remains polite, I'm not inclined to close the thread. |
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Putting GroundUrMast's explanation together with Dave Loudin, it is clear that your experience does not in any way contradict our understanding of antenna design or the accuracy of computer modeling of receiving antennas. To the contrary, your experience confirms them. |
perhaps even model it
Don't take statements of performance wrong most of the statements are comparing it to a non-fractalized (if that's a word) similar antenna.
You seem very interested in the characteristics of this antenna so why don't you take the leap and download 4nec2 (free modeling program) and give it a shot. (it's not that hard if you have an already built model) Here is the antenna you made with no reflectors (gain is dBi net) UHF Code:
max 7.0452717189 7.8089515597 with a flat reflector it's better. edit:changed gain figures to match the corrected model Code:
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CM Ruckman Fractal 2 bay bowtie then open it with 4nec2. The variables change the gap,separation,reflector distance. If you get stuck you could open a thread in the antenna section or enthusiast exchange area. Rather than discuss design in the help with reception area. |
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I did notice you called your model "Ruckman Bowtie". Mine is based on the overlapping triangle, or star shape. However, I do agree about moving to the other forum. I have a feeling I've overstayed my welcome in this forum <tongue in cheek>, and probably should have started there. I"ll probably post in the Enthusiasts forum later this week. My thanks to Dave Loudin, MisterMe, and especially GroundUrMast for not cutting my coax! |
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error in the model and gain figures
The model I posted had a wire not connected.
Sorry my eyes were tired when I finished it and I didn't notice until this afternoon. The model and the gain and SWR figures have been corrected. Bowtie /whisker: I'm pretty sure it's the model you posted links to like a stack of two wire whisker dipoles (with 3 extra bends to make it look like part of a star). All the whisker segments 3". BTW SWR in that range makes this model exceptionally flawed. It did alot better with one segment (accidentally) clipped off. |
I agree, this thread fits the Enthusiast's Exchange better than the Help With Reception.
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I'll meet you all in the Enthusiast's Exchange. I'll start a thread called "Fractal Fun", and hope to keep it just that!
BTW, I did download 4nec2, and maybe with some guidance, I can actually do a model, and get a tiny bit closer to your level of expertise. Maybe I should change my nick to TinkererPaul. Thanks again guys. |
One more correction
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GW 37 3 0 y 0 0 -y 0 0.0404 is an imaginary wire used to specify the feed point with the "EX" line below it. the last field in the line/card (0.0404) is radius in inches of 12 GA wire. (same as all the other wires) But models should be able to pass an AGT test (f-7 pick "far field pattern then look for the check box) So to pass the AGT test this model needs the radius of that imaginary wire to be "0.077" At least in the TV UHF frequency range. This also reveals another 0.6 dBi of gain. So be careful of models you find posted (or create) as this could be used to cheat even if inadvertently done. At the same forum dave pointed to there is a modeling thread here http://www.digitalhome.ca/forum/show...ighlight=4nec2 it's long and wanders a tad but the search function can weed out some of the less relevant stuff. As far as this fractal 2 bay whisker model I think the elements are to long (Because the SWR decays at higher frequency >ch.44). Most whisker antennas are 9-10 inches long (for uhf) these are 12" So the sections (not segments they are different) might be better at ~2.5" for a total wire length 10" per whisker. Overall applying fractals to an antenna does not increase gain/performance (at least that Ive ever seen). It's a mater of "how little do I lose if" game. The payoff is in smaller easier to stamp out antennas without giving up to much performance So fractals are generally compared to the parent design as a best you can do max. |
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