Most TVs these days and for couple decades have not real metal in them. Might have 3 prong plug, but the cases are plastic, components on a paper quality PCB. The safety prong on the AC plug might protect one against the metal F connector, but probably not due to it is often not grounded for RF and other electrical reasons.
Many TVs do not need a safety ground for not much to ground. Any radiation could come up the coax so it could be a problem. I have known some to open the plastic case and spray a shielding coating inside and also put aluminum foil inside to make a shield. Must be careful for the CRT type TVs still have the 1000s of volts in them. 73, ron, n9ee/r >From: wb7cjq <[EMAIL PROTECTED]> >Date: 2008/03/11 Tue PM 06:08:02 CDT >To: [email protected] >Subject: [Repeater-Builder] Re: Repeater input getting interference FROM a TV? > >This might sound too simplistic, after reading some of the other >responses. Is the TV grounded??? A lot of them just have a >polarized AC plug, not a grounded (3-pin) plug. AND, along the same >lines, is the AC outlet grounded??? I've found several 3- >pin "grounded" outlets in our house that have only a 2 conductor >cable feeding them!!! Might be worth a look. > >If the TV is looking for a ground, and assuming the dish is properly >installed (grounded), then the TV might well use the coax shield as a >ground, and at that point the coax shield could potentially radiate >the Sony's internal noises right to the roof. This would be easy >enough to check with a VOM and a cooperative owner. > >Would it be possible to disconnect everything but power from the TV >and see what happens??? Not to get too radical here, but could you >perhaps wrap the TV in 'grounded' tin-foil for a couple of minutes >and see if that knocks the interference down to below your noise >threshold??? That would be quick and dirty, but it might well save >you a lot of grief in putzing around with someone else's TV. > >Could you move the TV to a different foom for testing? Or perhaps >run an extension cord and power it from a different outlet? Just to >start crossing things off of the "list"... > >What about taking a walkie to the TV and "snoop" your repeater input >frequency and try to localize the source of the noise? You might get >lucky and be able to determine if the noise is going out via the AC >mains, or is actually being radiated from internal component that is >trying to be a 2-meter antenna. > >73, > >Dave. > >--- In [email protected], "raritansailor" <[EMAIL PROTECTED]> >wrote: >> >> Hi Folks, >> >> Here's a new one for me. In the same building as one of >> our repeaters there's a Sony TV hooked up to Dish/Echostar. >> The repeater is on 147.345/945. When anyone turns on the >> Sony TV hash is produced on the repeater input and locks >> up (keys) the repeater. It does not matter if the sat rcvr >> is on, off, powered off, or disconnected. The TV itself >> is producing the RFI. >> >> I put a DCI bandpass filter on the repeater input, but no joy! >> Yes, it would probably help if there was a PL on, but all that >> would do is keep the repeater from keying, not stop the noise >> if it was in use, or stop it from being "desensed" by the noise. >> (or at best the recieve ability dergraded). >> >> Any Ideas how to stop the noise at the TV? >> >> Regards, N3EAQ >> > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
