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Old 8-May-2019, 12:26 AM   #21
Junior Member
Join Date: Mar 2019
Posts: 10
Quote from rabbit73:

"It is possible that you have some interference that is conducted through the power line, but you most likely also have some radiated (through the air) noise interference that is picked up by the antenna.

First, make sure that the coax is grounded with a grounding block that is connected to the house electrical system ground; it might help. Next, use a portable battery operated radio tuned to a vacant channel on the AM broadcast to hunt for sources of radiated noise interference, as I mentioned in post #7. Most AM portable radios have a loopstick antenna that is directional which will help you locate the interference source. "

I had to return to Phoenix and won't be up to the Cabin in Show Low for a few weeks. However, based on some additional testing before I left these were my findings:- (Don't know if they make sense to anyone, I guess RF noise/interference stuff isn't necessarily logical :-)

1) Grounded the Antenna coax lead at the TV to house ground as suggested but noted no difference in signal quality.
2) With an old analog AM portable radio tuned to no station and just listening for static type noise I noticed :-
a. Major interference coming from my powered up laptop which is located below the television. Noise to the extent that Channel 3 K0FB is blocked and cannot be scanned (laptop is used for streaming - e.g. U-tubeTV, Netflix, remote access to Hauppauge on home computer etc.)
b. With Laptop powered down from keyboard but AC power supply still plugged in, significant noise is detected from both the TV (inexpensive older Scepter 40" LCD) and remote laptop switching power supply. However, moving the laptop switching power supply and it's AC/DC output wiring around from the proximity of the TV, K0FB channel 3 would pop-up but remain somewhat pixalized, moving the switching power supply in a certain direction and location reduced the pixalization to a watchable channel.
c. With Laptop powered down and switching power supply unplugged from the wall, interference was minimal until I moved the power supply and wiring in front of the TV when significant pixalization would return (note, no power is applied at this time), moving the Laptop switching power supply to it's previous location and signal improved with minimal pixalization.

I can live with powering down the laptop to reduce interference when watching OTA K0FB channel 3 but would like to find a decent solution to block interference from the laptop switching power supply and cabling (best location from my testing was to place the physical switching power supply in front of the stone fireplace which won't work long term for the wife :-)

Many thanks for all your feedback and comments/recommendations to date!

Peter Johnson
Phoenix, AZ
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