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Old 10-May-2019, 8:04 PM   #28
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,708
Originally Posted by Johnsonbrits View Post
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 :-)
Thank you for making the thorough tests; you are on the right track.

Interference problems can be difficult to solve. Interference can be conducted, radiated, or both and you can have more than one source of interference.
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.
That's interesting. Am I understanding it right? With the laptop off and its power supply not plugged in, you still have interference? That would indicate another source of interference besides the laptop power supply.

My original thought was that the primary source of interference is from the laptop power supply.

Does the laptop have an internal battery? Does the laptop cause interference when it is running on its battery and the power supply is not plugged in to AC and not connected to the laptop?

Are you using the TV tuner or the Hauppauge tuner to receive channel 3?
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 :-)
There are two types of power supplies: linear and switching. The older linear power supplies are heavier because they have a power transformer, are less efficient, but don't create much interference. The newer switching power supplies are lighter, much more efficient, but can create a lot of interference if not properly filtered in the original design. In some countries, switching power supplies are required because of their better energy efficiency.

In theory, it is possible to substitute a linear power supply for the switcher; lower efficiency, but less noise interference.

Can you bring a newer laptop up to the Cabin for a test? The AC adapters for the newer laptops have better filtering.

How far away from the TV is the antenna, the direct distance, not the coax length?
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 11-May-2019 at 10:58 AM.
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