[RFI] LCD TV wipes out AM BC band

[Dale Svetanoff]

A bit of news I discovered early today:  I have a 19 inch Toshiba LCD HDTV that serves double duty as a TV and as my computer monitor.  I've had the set for about a year and a half and like it very much.  I have posted some prior comments on this reflector about Ethernet radiating from the set when OFF, and reduced when ON.  Other than that, I've had no RFI issues with the set until now.

This morning, I brought my RCA (used to be "GE") Super Radio III into the computer room for the first time.  (I usually use that radio in another room, well-removed from the computer room.)  None of the computer equipment, including the monitor, was on when I walked into the room with the radio.  I had the radio tuned to WBBM-AM in Chicago on 780 kHz, one of my favorite stations.  (For those not familiar with the Super Radio, it is a "hot" portable AM/FM set that is large, very sensitive [with a tuned RF stage ahead of the mixer], and big ferrite rod antenna to help pull in the distant stations.)  I powered up the monitor and not only was WBBM wiped out, but so was most of the AM band!  To make certain that it was the Toshiba set causing the problem, I cycled its power on and off 3 times.  Yep, it was the problem.  BTW: The radio was running on internal battery power.

Since the radio is a "hot" set, the hash from the monitor/TV blanked out a good portion of the AM band for a distance of at least 10 to 15 feet inside my house.  Rotating the radio to minimize the TV set hash did reduce the severity of the interference, but it also reduced WBBM's signal strength.  As you probably know, FCC Part 15 does not require radiated emission testing at 1 MHz, so whatever the set radiates, too bad.  Of course, the radio has a Part 15 label that says it must accept interference.  I suspect that not one of the FCC commissioners has ever tried to listen to actual radios when they were receiving interference.

I'll be the first to admit that sadly, the Super Radio III is a piece of junk (see my eHam review).  However, the crummy aspects of the radio have nothing to do with what I heard this morning.  I do operate on the 160m band, and have done so when the Toshiba set is running.  I have heard zero interference from it on that band, but then again, the distance between the TV set and my 160m Carolina Windom is at least 75 feet - maybe more.  (This is why K9YC, myself, and others have made comments that it is not where equipment is located relative to each other, but where offending equipment is located relative to antennas.)

There are 2 reasons why I am making this post:  1) I would like to know if anyone else on this reflector has experienced AM broadcast band (or 160m band) interference from an LCD TV set or monitor.  If so, brand or model of set and distance over which it caused problems.  2) Most posts I have read (or made myself) have given LCD sets a clean bill of health regarding interference.  Prior to this morning, I have never had anything other than a 2m HT near the set.  I knew it had to be too good to be true!

Please note:  I am not on a witch hunt of "bad" LCD TVs.  Overall, I truly feel they are quieter than plasma sets and there does not seem to be any great number of hams complaining about RFI from the sets or TVI to the sets.  That's great.  Some of us do listen to one or more AM broadcast stations at various times, so it might be good to know if there are any other sets out there that can give a surprise if you bring a sensitive portable AM receiver near the TV.  I suspect my Toshiba is not alone in this situation.

73, Dale
WA9ENA      


Dale Svetanoff
svetanoff at earthlink.net
EarthLink Revolves Around You.