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  #46  
Old 02-21-2014, 04:03 PM
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old_tv_nut old_tv_nut is offline
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Quote:
Originally Posted by vts1134 View Post
I received my new modulator and it too has the same symptom when broadcasting on channel 3, so I gave up the dream and hardwired all of my sets. On the plus side they look FANTASTIC with a hardwired signal. I have most of them completed now, and will hopefully wire the remaining sets this weekend. I am not quite done with my modulators though . I started a new thread that might be interesting here http://videokarma.org/showthread.php?t=260846
This still seems to be something like a switch-mode power supply that radiates in your channel. Really, you should take a portable TV and go around your place to see where it is strongest. You may be able to locate it and fix it. Worth the effort if you don't have to hardwire more sets in the future.
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  #47  
Old 02-21-2014, 07:28 PM
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Quote:
Originally Posted by old_tv_nut View Post
This still seems to be something like a switch-mode power supply that radiates in your channel. Really, you should take a portable TV and go around your place to see where it is strongest. You may be able to locate it and fix it. Worth the effort if you don't have to hardwire more sets in the future.
This would only be possible if it were A: battery powered, or B: in a neighbor's home as I have killed power to every last thing in my house except modulator, source, and monitor with no change.
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  #48  
Old 02-21-2014, 08:16 PM
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Have you tried any ferrite filters on the line cord or the coax output of the B-T? They work well for keeping undesired signals out of equipment.
http://www.amazon.com/Ferrite-Core-C...ferrite+filter
not affiliated,
jr
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  #49  
Old 02-23-2014, 02:27 PM
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I did not see this specifically mentioned in this topic, so here is one thing that may have worked with this problem for me: Try plugging the modulator into one of those "grounding adapters" that have only two prongs, to eliminate the ground connection from the modulator to the building. Then, use a DVD player or VCR (also with its two-prong cord) as the signal source. (Do not have the VCR connected to any cable box or antenna system, just standing by itself.) Let me know if you tried this already.
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  #50  
Old 02-24-2014, 07:54 AM
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Originally Posted by ChrisW6ATV View Post
I did not see this specifically mentioned in this topic, so here is one thing that may have worked with this problem for me: Try plugging the modulator into one of those "grounding adapters" that have only two prongs, to eliminate the ground connection from the modulator to the building. Then, use a DVD player or VCR (also with its two-prong cord) as the signal source. (Do not have the VCR connected to any cable box or antenna system, just standing by itself.) Let me know if you tried this already.
I tried this as well.
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  #51  
Old 04-16-2014, 04:22 PM
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Originally Posted by N8NM View Post
That definitely sounds like a local interference problem. By any chance, is your house connected to cable TV?
AND, by chance is there a local *digital* channel 3 broadcasting within 15 miles of your house? If I missed this in someone else's previous post I'm sorry. I read the entire thread.
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  #52  
Old 04-16-2014, 04:34 PM
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Quote:
Originally Posted by old_tv_nut View Post
See the section on "feeding a dipole antenna"
http://en.wikipedia.org/wiki/Dipole_antenna

I presume your matching transformer is 75 ohms (your coax side) to 300 ohms (your dipole side)? According to the above you should not be using a 75 to 300 ohm matching transformer unless you use a folded dipole.
I built a 75 ohm FM antenna out of 75 ohm coax just as given in the first figure of the wiki attachment. I did include a triple loop right at the antenna to provide some isolation between my flea power transmitter and the antenna.
It's a pretty efficient antenna, scared me when I drove around the neighborhood and could pick it up almost a mile away! I lowered the output power with a 10dB coax pad. Attached is a picture.
Attached Images
File Type: jpg FM ANTENNA 60.75 inch 75 Ohm FM Dipole .JPG (36.9 KB, 9 views)
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