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!

Regards,
Peter Johnson
Phoenix, AZ

Switching power supplies are a common culprit for creating interference into the VHF frequencies. https://en.wikipedia.org/wiki/Switch...e_power_supply

Is the power supply OEM to that laptop or an aftermarket replacement. If not OEM, then that's the first thing to consider replacing. Or, you could bring along a metal container to drop it into and see if you can suppress the radiated emissions that are interfering with reception.

Other options include maximizing distance between that laptop and its power supply relative to the antenna or, perhaps, relocating them (or the antenna) so they are at somewhat of a right angle to the antenna.

Perhaps a new laptop?

I’d try two of these:

https://www.mouser.com/ProductDetail...CABEgIC1PD_BwE

Put one on the power cord close to the power supply, the other on the DC cable; again close to the power supply end of the cord.

You may also find these on old VGA monitor cables.

Thanks for the recommendation, I've placed an order for ferrite core suppressors and will try them on my next visit to the cabin.

Peter

ADtech, The Laptop is an ASUS unit that was given to me by my son-in-law. I believe the power supply is original but will need to verify on my next trip up to the cabin.

Good idea! - I have an empty cookie/biscuit tin that I'll place the switching power supply into as a test on my next trip up to the cabin. Does the tin need to be grounded?

Peter

be 4 you do that by putting it in to a tin ask your
Local firer department be for it goes up in smoke and you loos ever thing
Including your cabin ask the manufacturer what they Suggest be 4 u put it in
A TIN!!!

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.
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?
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?

Use a solar panel change or a battery backup pack like a jump box for back up POWER
To charge up the international battery on the laptop there is all kinds of stuff on the
Internet for like RV camping but it is all 12volts stuff and so is the labtop. I think that
Maybe something
like this will fix your problem.We'll good luck and have a good day.
HAPPY mother's day everyone on the form!!!

I'm betting the ferrite cores are going to help a lot. I use them at work when faced with un-explainable issues on computer equipment. Sometimes it's just like magic.