How to stop interference in TV antenna signal

Thread Starter

Finndersen

Joined Aug 5, 2017
5
I've finished a custom modded TV project you can see here: http://m.imgur.com/a/nIBqT
I basically replaced all the internals of an old CRT TV
I want to use the existing antenna with a digital tuner to be able to view TV stations.
As you can see from the album, I got it working while building it with everything open. I just got a coax cable, cut it in half, stripped it a bit and soldered the middle bit to one of the terminals after the ferrite core windings (or whatever it is) at the antenna, and the insulating/ground part to the other terminal. Then plugged the end of the cable into the tuner

However when I finished the system and closed it up with everything inside, it wouldn't pick up signal anymore. I figure it's either wired inappropriately so it's very sensitive to disturbance (something needs to be grounded or isolated or something idk) or other components are generating EMI and causing issues

Is anyone able to help isolate the problem and how to fix it??

Cheers

Screenshot_20170805-155823.jpg


Mods Edit:
Please post the photos and images with *.jpg file, the format .png just good for the graphics only have the vertical line and horizontal line, when you post the wrong file format then the file size will be bigger than 10 times as this file with png and converted to jpg from about 1.4Mb to 1.39Kb.
 

ian field

Joined Oct 27, 2012
6,539
I've finished a custom modded TV project you can see here: http://m.imgur.com/a/nIBqT
I basically replaced all the internals of an old CRT TV
I want to use the existing antenna with a digital tuner to be able to view TV stations.
As you can see from the album, I got it working while building it with everything open. I just got a coax cable, cut it in half, stripped it a bit and soldered the middle bit to one of the terminals after the ferrite core windings (or whatever it is) at the antenna, and the insulating/ground part to the other terminal. Then plugged the end of the cable into the tuner

However when I finished the system and closed it up with everything inside, it wouldn't pick up signal anymore. I figure it's either wired inappropriately so it's very sensitive to disturbance (something needs to be grounded or isolated or something idk) or other components are generating EMI and causing issues

Is anyone able to help isolate the problem and how to fix it??

Cheers

View attachment 132316


Mods Edit:
Please post the photos and images with *.jpg file, the format .png just good for the graphics only have the vertical line and horizontal line, when you post the wrong file format then the file size will be bigger than 10 times as this file with png and converted to jpg from about 1.4Mb to 1.39Kb.
My best guess is; the ferrite doofer is a balun that combines the twin feeder with the co-ax feed. If you're not using twin feeder - strip that bit out.

On decoded digital; the screen is no different between no signal, and signal blotted by noise - most just show a blue screen.

If you're getting a signal - the decoder tries to display as much as it can make sense of - the picture pixellates or goes "blocky" when weak or interfered with.

Analogue sets usually only show noise that fits through the pass-band, but it doesn't have to be in band to wreck a signal that's tuned into.
 

Thread Starter

Finndersen

Joined Aug 5, 2017
5
My best guess is; the ferrite doofer is a balun that combines the twin feeder with the co-ax feed. If you're not using twin feeder - strip that bit out.

On decoded digital; the screen is no different between no signal, and signal blotted by noise - most just show a blue screen.

If you're getting a signal - the decoder tries to display as much as it can make sense of - the picture pixellates or goes "blocky" when weak or interfered with.

Analogue sets usually only show noise that fits through the pass-band, but it doesn't have to be in band to wreck a signal that's tuned into.
What's the twin feeder vs coax feed? The aerial is just a single telescopic thing, coming out of the bottom right of the picture
 

ian field

Joined Oct 27, 2012
6,539
What's the twin feeder vs coax feed? The aerial is just a single telescopic thing, coming out of the bottom right of the picture
The most common use of a balun is to couple co-ax to balanced feeder - your picture looks like there's a balun.

the very basic wire loop antennas sometimes have a balanced feeder - most setmakers don't bother and just stick a bit of co-ax on it.
 

Thread Starter

Finndersen

Joined Aug 5, 2017
5
The most common use of a balun is to couple co-ax to balanced feeder - your picture looks like there's a balun.

the very basic wire loop antennas sometimes have a balanced feeder - most setmakers don't bother and just stick a bit of co-ax on it.
Ok, there used to be a twin line coming from the antenna to the analogue tuner. I've bought a matching transformer to convert from twin line to coax, I'll see how that goes
 
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