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Interference to telephones and tv`s

 
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Interference to telephones and tv`s
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stylzmovement
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Joined: 11 Oct 2003
Posts: 142

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Post Interference to telephones and tv`s Reply with quote
my transmitter is causing interferance to telephones and televisions in the buildin that i am in,
my broadcast frequency is 96.7 fm
i can hear the program on on the lower parts of the fm band and also on the 2nd harmonic 193.400Mhz
also on the 5 th harmonic 483.500Mhz
what can i do about this , can i install an external filter or some sort of tuning stubs ?
Thu Jan 15, 2004 10:41 am View user's profile Send private message
pcs
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Reply with quote
Q: : If I use filters I can put my antenna right next to my neighbor's TV antenna without any problems right?

A: Wrong! The low pass filters only attenuate harmonics. If harmonics are not the cause of your problem (they almost never are - our exciters are very clean!) removing them won't help. What causes 99% of all radio interference problems? YOUR FUNDAMENTAL SIGNAL!!! A high power fundamental signal in CLOSE PROXIMITY to ANY type of receiving equipment (TV, radio, telephone, PA system etc.) will blow right past any tuner or filtering on this equipment and enter the amplifier stage along with the intended signal where it will cause interference. This type of interference is called "fundamental overload". All the harmonic filters in the world won't help in this very common situation. What will help? Increase the standoff distance (vertical, horizontal or both) between your antenna and what you are interfering with. This is one of the many reasons high power FM radio station antennas are located on high towers. A 100 KW radio station with a 20' antenna would cause a lot of RFI even though the harmonic levels meet FCC requirements.

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Thu Jan 15, 2004 9:51 pm View user's profile Send private message Visit poster's website
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