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Author Topic: TV RFI when keying up on 2 meters  (Read 3347 times)
KK4SUH
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Posts: 15




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« on: December 02, 2013, 06:51:08 AM »

I get TV OTA using two dipoles in the attic;an old 11 meter dipole somebody gave me a few years back and a vhf dipole I recently made that feed into a T connector which is connected to the coax that feeds into my TV's (I know it sounds crazy, but I had to use them together to get most of the stations available to come in.)  I did have an amplifier on the line that I have since removed that has improved the situation a bit (I no longer completely overload the receivers on the TV's when keying up) , but even if I just key up on my HT on 1W it still causes problems with channel 7.  It only occurs if I key up from around 144.600 to around 145.900.

Would a notch filter work, and where can one be purchased for the 2M band?
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KB4QAA
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Posts: 2419




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« Reply #1 on: December 02, 2013, 10:21:48 AM »

Unlikely you will find a single channel notch filter for sale, though one can easily be built.  Without looking up the present TV channel frequencies, a Band Pass filter (probably Low Pass) may work.   Possible sources: 

DX Engineering,

Morgan Manufacturing   http://www.morganmfg.us/   


The standard list:
-Reduce power
-Re-orient the antenna
-move the antenna further away/higher
-Tidy up:  straighten out (TV) cables, power cords, don't overlap, coil up unused lengths, attach chokes close to TV (that appropriate Mix for the frequencies in question).

-place covers or even aluminum foil over any cable F type connectors not in use.

-Simplify your setup for troubleshooting.  Remove the second TV antenna.  Work with only one antenna.   

-Borrow a different TV and see if it has the same interference.

Realistically, a 1w HT shouldn't cause interference to a TV.  If all else fails you may need to get a different TV, or coordinate your hamming so as not to bother the family.
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KK4SUH
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Posts: 15




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« Reply #2 on: December 02, 2013, 11:36:26 AM »

I started by removing pieces of coax to reduce number of connections and overall length and channel 7 went completely out. I tried only using one antenna, no luck.  I did try another TV this morning and it experienced the same interference. I don't have any extra chokes on me right now, so I couldn't try that. I haven't tried moving around the antenna yet as it's a bit of a pain to move around but I'll try it when I get a chance.
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KF7CG
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Posts: 840




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« Reply #3 on: December 03, 2013, 06:33:31 AM »

Go to a frequency chart an find the frequencies for channel 7. I believe that it is just above the 2Meter band. The frequencies mentioned might be an image to channel 7. It also sounds as thought 7 is somewhat marginal in your area, again a problem.

You need, if you can find one, a 2 meter band-reject fileter for the TV antenna feed. Place it as close to the TV as possible.

KF7cg
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KH2G
Member

Posts: 314




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« Reply #4 on: December 03, 2013, 10:41:31 AM »

Toss the TV and get on with life. No one needs a one eyed monster. The old ones that had power transformers at least were usable for junk parts.
Regards,
Dick KH2G
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