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Author Topic: Vertical Antenna interfering with neighbors over the air tv broadcast?  (Read 832 times)

KL7CW

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  • Posts: 1162

Tom here are a couple of ideas to investigate.  Back in the 50's and 60's when we had only OTA TV, sometimes if there was only minor RFI, like some lines, bars, and some sound effects, often the problem could be solved by simply making sure the OTA antenna was aimed in the correct direction, had good coax or twin lead, good connectors, and not too many splitters.  If you have a good OTA antenna, try it on your TV and see what happens.  Back in twin lead days, often the feed was very degraded, or often only one of 2 wires were still in place.  A good strong signal into the TV may or may not override MINOR RFI.  A pre amp at the TV antenna may or may not hurt or help your situation.  If the problem is just overload (too much RF into the TV) this could be getting into the TV via the antenna, so a high pass filter at the TV antenna terminals might help.  However since you are so close it is also quite possible that your RF is getting directly into the TV, not through the antenna connections.
    Glenn had a good thought.  How is your power maintained at 70 watts.  If it is through the ALC circuits it is possible that your drive is set too high, there is an overshoot, and the the ALC circuit cuts back on the power after a short interval.  I am not an expert in this area, it is just another idea to investigate. I would carefully read up on your FT-8 setup and make sure all is OK, however even if not it does not seem highly likely that this would cause VHF/UHF radiation from your TX.  Is 70 watts an appropriate power for FT-8 with your transceiver ?. 
    Back in the dark ages, just demonstrating that a TX did not cause RFI to a TV set hooked to a portable antenna set up near the neighbors house knocked the wind out of the neighbors sails, and they either fixed the problem, lived with it, or complained to everyone. Try to be helpful, but think twice about touching the other persons stuff.  Nearly 100 percent of consumer products are subject to part 15 FCC regulations, which briefly says that the device must not cause RFI and must accept RFI from any properly functioning radiator, such nearly 100 percent of ham equipment for many years now. I would print up a copy of the part 15 regulations, probably available from ARRL and/or FCC web sites. 
     I am not a lawyer, so my wording of the regulations may not be completely correct.
                    Good Luck   Rick  KL7CW       
 
   
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WB6BYU

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  • Posts: 20896
    • Practical Antennas

Are they using a pre-amp on their TV to pick up the signal?

I was working on one case where the neighbors had a preamp
and 4-way splitter in the attic, with long runs of twinlead running
to TVs in the 4 corners of the house.  That picked up so much
RF from the HF transmitter next door that the amp saturated,
eliminating the signal.  (The station they were trying to receive
was from >60 miles away.)

By removing the unused twinlead feedlines, and choking everything
going into and out of the preamp, we made it tolerable.

AC9XH

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  • Posts: 32

my experience is that i lowered my power output. I run qrp since moving to this town. everyone seems to have the junk new tvs that pick up anything over the air.I agree on different points.
1. make sure you dont have sharp edges or frayed feedline or dipole wires.
2. so close to neighbors antenna, 70 watts will definitely wash it out with frontend rf overload. tvs dont have the best front ends. I used to repair them for a living a long time ago.
3.even though ft8 is not a low powered mode, most people are running 5 watts or less. I run 2 1/2 watts from my phaser transceiver and i work all over the world. band open lots of contacts. band closed not even 1kw will get you out of the country.You can tell the qro guys the trace on the waterfall is wide enough to look like darth vaders light saber.

4.back to power levels. alc? ok? you might be splattering all over with unwanted harmonics.How do you control it with an older rig. meaning what do you have to monitor it?

5. older rig does it have tube finals? check your neutralization, and check the filter network internally.

6. lower your power. I can wash out my new lcd tv from walmart with 30 watts on certain bands. i cranked the power down to 5 watts and not even a hint. proving front end overload.
7.lower your power.

8. NEVER NEVER TOUCH YOUR NEIGHBORS TV.If it goes out later,they will try to sue you in small claims court for damages since you touched it and are not a tv repairman making a living doing it.
for being neighborly, i would lower your power significantly.

9. lower your power. common sense theory transmitting antenna less than 50 ft away pushing 75 watts into an antenna ,im assuming has a gain of 3db to it,WILL CAUSE INTERFERENCE. No matter what guru tells you otherwise. you can clamp toroids, you can put in low pass filters you can buy the most expensive shielded coax and ground ground ground and still interfere. Why? because you are close to your neighbor and in the middle of watching wheel of fortune,it washes out. even if,its not you you must lower your power to be a good neighbor,to show that the amateur community cares about the purity of our signals andmost important, enlist the help of another ham to actually eyeball the interference when your radio is being keyed up on ft8.My guess is since your neighbor has the latest greatest tv the frontend is washing out due to rf overload. too much rf to be filtered out and the rf bleeds thru to the next circuit inline either directly or thru the ground of the cable ,etc since their tv will not be grounded like your station.
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