powerline yagi hunting
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Here is an estimated tvfool report based on your zip code: http://www.tvfool.com/?option=com_wr...e6a453aa51dd91 Some people have been waiting a long time to post; there is a shortage of moderators. I can't help with that, but I'll try to help you with your channel 2 KJWP problem. The noise level from electrical interference is high on VHF-Low (channels 2-6), which makes reception of digital channels more difficult than analog channels were. That is why there are so few transmitters on VHF-Low. Some of the stations that stayed on VHF-Low after the transition from analog to digital, have had problems with reliable reception. Some have been allowed to increase their power, and some have had to move to VHF-High (real channels 7-13). Now that the FCC is giving some of the UHF channels to cellular services, there will be more pressure to use VHF channels for TV broadcast. I looked at your thread in the link that you gave, and also your first thread there: http://www.satelliteguys.us/xen/thre...n-help.367751/ I can give you a design for a Fox Hunting 3 element yagi made with PVC and steel tape measure elements, but you would need a receiver connected to the antenna to measure the power line noise on VHF. The best tool that I have found is a battery operated portable radio that tunes the AM broadcast band. Its built-in loop antenna can act as a direction finder. Tune it to a vacant frequency at the low 540 end or the high 1600 end and listen for noise. If the noise is loud on AM broadcast, it will usually be strong on VHF TV. An FM portable radio doesn't work as well, but a radio that tunes the aircraft band will work because it is AM. MFJ makes several power line noise meters, but the quality control isn't very good. Read the eHam.net reviews for tips. https://www.google.com/#q=mfj+power+line+noise&* Quote:
If there is a defect in the power line, maybe the power company can fix it if they can find it. If the power line noise can't be reduced, then you will have to find a way to increase the signal relative to the noise. An antenna with more gain will help. Grounding the coax with a grounding block might help, but the antenna itself will still pick up the noise. Moving the antenna to another location might help; having it behind a power line couldn't be good. You might have to do without KJWP. I'll send another PM with antenna ideas. |
Channel 2 is 54 to 60 MHz. I cut a folded dipole for mid channel.
5540/57 = 97.2 inches. http://i496.photobucket.com/albums/r...psna1exzcg.jpg http://i496.photobucket.com/albums/r...pspundvae4.jpg http://i496.photobucket.com/albums/r...psjau7aw8l.jpg If you want to design your own yagi with aluminum tubing, you can do it here: http://www.k7mem.com/Electronic_Note.../yagi_vhf.html http://www.k7mem.com/Electronic_Note...vhf_quick.html http://www.k7mem.com/Electronic_Note..._vhf_feed.html |
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The 5540 is just to convert the feet formula for a half-wave dipole to inches. 468/57 = 8.21 feet = 98.5 inches But I have found by experiment that is a little too long for VHF and UHF because of the end effect and length to diameter ratio of the conductor. "Fatter" conductors don't need to be as long for the same resonant frequency. |
nomorecomcast
I am not able to answer your last PM because it says your folder is full. It is not worth your trouble to build a yagi for hunting power line noise if you don't have a receiver to connect it to. Here are some links about that: http://www.homingin.com/equipment.html http://theleggios.net/wb2hol/projects/rdf/tape_bm.htm http://www.arrl.org/files/file/Technology/HANDSON.pdf But, I think it is worth the trouble to build a channel 2 or channel 6 yagi to see if they will make the signals stronger compared to the power line noise. |
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You can use heavier gauge wire or tubing, but that would be more expensive. Here are the calculations for the Channel 2 yagi: Channel 2 Yagi, 57 MHz 5540/57 = 97.19 Reflector 97.19 x 105% = 102.1 inches Director 97.19 x 95% = 92.3 inches One wavelength in air is 11810/freq in MHz = 11810/57 = 207.19 inches DE to Reflector spacing = 0.2 λ = 207.19 x 0.2 = 41.4 inches DE to Director spacing = 0.15 λ = 207.19 x 0.15 = 31.1 inches λ (Lambda, Greek) is the symbol for wavelength Here is a channel 6 yagi for WPVI: http://forum.tvfool.com/attachment.p...1&d=1488054757 and the calculations for the channel 6 yagi for WPVI: Channel 6, 82 to 88 MHz, center frequency 85 MHz. 5540/85 = 65.2 inches length for a folded dipole antenna To convert the dipole antenna into a 3 element beam for more gain, add a reflector and a director: Reflector is 105% of Driven Element = 65.2 x 1.05 = 68.5 inches Director is 95% of DE = 65.2 x 0.95 = 61.9 inches One wavelength in air is 11810/freq in MHz = 11810/85 = 138.9 inches DE to Reflector spacing = 0.2 λ = 138.9 x 0.2 = 27.8 inches DE to Director spacing = 0.15 λ = 138.9 x 0.15 = 20.8 inches Here are some hourglass loops for VHF-Low designed by holl_ands who does antenna computer modeling: http://imageevent.com/holl_ands/loop...673fd1.eagle_s for very tall attics |
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