Noise Source Finally Found (2-3 MHz) !

BOBRR

Member
Premium Subscriber
Joined
Dec 15, 2004
Messages
1,164
Location
Boston, MA
Hi,

Just thought I'd post this here, as might be of interest to others.

Have been for some time now trying to track down a significant noise source on 2-3 MHz, am.

Looked at most everything I could get to; did all the plug and unplug wall warts, etc.

Finally found it !

We have a very old color CRT TV (small; 14" drag.) TV in the downstairs Kitchen.
Comcast box feeding the TV (via coax) , which also picks up the hand-Remote for the channel switching.
Pretty typical setup, other than the age of the TV, and the fact that it's a CRT.

That was doing it.

All my radio receiving gear (RSPdx) is upstairs; a pretty fair distance.
Really surprised.

Just so I might learn:

Do you think the noise was being propagated back thru the 110 V Ac line cord going to the TV ?

Or, just radiating thru the air as it has as expected a simple plastic case.
Surprised it would do so, as my main receiving ant. is outside the house (simple long wire; Balun at end, and coax run to upstairs)
which is probably a good 40 feet or so from the TV.

Or, directly from TV to the RSPdx ? Or,...?

How do you think the RSPdx is picking up this noise ?

Think any Ferrites would help ? If so, where should be placed ?
Wife loves the TV, so replacing it not a viable option. Any line filters, etc. that you think might help ?

Thoughts on would be appreciated.

Regards,
Bob
 

bharvey2

Member
Joined
Mar 12, 2014
Messages
1,412
It's possible that the RF noise is induced into the AC electrical system. I had a similar encounter. I'd walk around with my handheld SW radio and as soon as I'd approach an outlet or switch, the noise would increase. I could pass the radio along the path of the romex (electrical wiring in the walls) and the noise would track right along the wiring path. The RF noise was intermittent so I never did find the source. However, I did find that I could reproduce a similar problem with a cheap wallwart/switching power supply.
 

popnokick

Member
Premium Subscriber
Joined
Mar 21, 2004
Messages
2,088
Location
Northeast PA
If you are unwilling to replace the TV set there are probably many other complicated and likely expensive solutions that may or may not work. Disconnecting and replacing the set is the action that has the highest probability of expeditiously eliminating the RFI.
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
23,268
Location
Bowie, Md.
The problem comes in where the noise might not just be routed into your home electrical system, the entire TV or something within it could be the culprit. Even the CRT itself might be at fault. In this case the RFI would be radiated all over the place, and the home electrical system is picking it up as an unintended re-radiator.

That's a toughie to get rid of...Mike
 

jonwienke

More Info Coming Soon!
Premium Subscriber
Joined
Jul 18, 2014
Messages
12,137
Location
VA
The flyback transformer in the TV is probably the culprit. It's probably time to look into retiring it.
 

wtp

Member
Joined
Apr 3, 2008
Messages
3,133
Location
Port Charlotte FL
as i kid cable came to our neighborhood, mom wanted it, so we got it.
i realized they had taken the rabbit ears off, and i thought one day that putting them on might do something.
it did, if i put the TV in the kitchen on channel 3 and turned the antenna just right we now had cable in the kitchen.
we just had to watch what was on the other set.
the RF on the cable box is a little transmitter after all.
so,
is the antenna disconnected ?
 

iMONITOR

Member
Premium Subscriber
Joined
Sep 20, 2006
Messages
8,459
Location
MACOMB, MI.
You can buy a NEW 14" LCD Digital TV for about $50. Christmas is coming! Tell the wife you really love and appreciate her and you're getting "HER" a new T.V.! :love:
 

ecps92

Member
Joined
Jul 8, 2002
Messages
11,469
Location
Taxachusetts
Why wait, Black Friday on-line sales this year, should have some interesting attention grabbers. :)
You can buy a NEW 14" LCD Digital TV for about $50. Christmas is coming! Tell the wife you really love and appreciate her and you're getting "HER" a new T.V.! :love:
 
Top