Mike, Does this problem occur on one channel or all???
If only on one then the TV's LO might be the problem. TV IFs are 41-47 MHz with the video carrier at 42.25 MHz. I think the LO would be 45.75 MHz above the channel freq. Ch 3 is 61.25 MHz. Since so much these days uses some type of converter box the TV might stay on Ch 3 or 4. The Nelson ratings boxes that log what you watch uses this info to determine what channel you are watching. The Germans in WWII also looked for the rcvr LOs to detect near by ships. If on all channels then something other than the TV's LO and would be another oscillator/ossillation inside. This might be an issue the TV manufacture knows about. The way the interference specs were written long ago was a manufacture was responsible for interference, but only had to correct if a problem occurred. Did not have to spend the money on all TVs made by installing filters, but had to correct if occurred. Might give them a call. 73, ron, n9ee/r >From: raritansailor <[EMAIL PROTECTED]> >Date: 2008/03/13 Thu AM 06:04:14 CDT >To: [email protected] >Subject: [Repeater-Builder] Re: Repeater input getting interference FROM a TV? > >I had tried the HT sniffer method, but it seemed to come from the TV >as a unit, and was not any better/worse at a given lead. > >I've got to get the SpecAn involved and find out what exactly this >thing is radiating, and try to relate it to some fundemental >operation of a TV, and go from there! > >Tnx > >Mike - N3EAQ > >--- In [email protected], Ron Wright <[EMAIL PROTECTED]> >wrote: >> >> Mike, >> >> Maybe you've tried this, but taking an HT on your input freq and >sniffing around the TV might give idea of where it is coming from. >Might be on power cord or antenna. >> >> If on power lead could put simple inline wrap cord around choke. >Would act as low pass filter. >> >> On antenna lead might need a simple notch using a piece of 1/4 >wavelength RG59 tuned to your input freq with T connector. Simple to >make and sure it would blend in nicely. >> >> 73, ron, n9ee/r >> >> >> >> >From: raritansailor <[EMAIL PROTECTED]> >> >Date: 2008/03/12 Wed AM 05:59:01 CDT >> >To: [email protected] >> >Subject: [Repeater-Builder] Re: Repeater input getting >interference FROM a TV? >> >> > >> >Unfortunately the TV belongs to the folks who are allowing us to >use >> >the site for free. I really dont want to bend their noses :-) >> > >> >I've discussed replacing the TV, but they're not keen on that >answer. >> > >> >Yes, I am a bit gun shy WRT ripping into their set, I hope some >> >chokes on the leads buy me something! >> > >> >Thanks! >> > >> >Mike >> > >> >--- In [email protected], George Henry <ka3hsw@> >> >wrote: >> >> >> >> Be VERY careful about doing the work on someone else's >property... >> >there are liability issues! (If their TV catches on fire down the >> >road, guess who they'll come after....) >> >> >> >> Best bet is to offer suggestions such as Jeff posted, even offer >to >> >pay for the filters, but the bottom line is that it is 100% the >> >responsibility of the owner of the interfering device to eliminate >> >the interference or discontinue the use of the device, when >> >interference occurs to a licensed service. Send 'em to the ARRL >> >website: lots of good information for consumers there, and the >FCC >> >even directs people there! >> >> >> >> You might even want to print out the FCC warning letter that >went >> >out to the owner of a TV set that was interfering with the EPIRB >> >satellite system recently. That oughta scare 'em into doing the >> >right thing! >> >> >> >> George, KA3HSW / WQGJ413 >> >> >> >> -----Original Message----- >> >> >From: Jeff DePolo <jd0@> >> >> >Sent: Mar 11, 2008 9:34 AM >> >> >To: [email protected] >> >> >Subject: RE: [Repeater-Builder] Repeater input getting >> >interference FROM a TV? >> >> > >> >> >> Any Ideas how to stop the noise at the TV? >> >> >> >> >> >> Regards, N3EAQ >> >> > >> >> >The most direct solution is obvious: replace the TV. >> >> > >> >> >If that's not an option, try choking the coax/video and power >> >cords going >> >> >into the TV with ferrites. Pick a mix that provides optimum >> >attenuation at >> >> >VHF. You might also try disconnecting the coax or video/audio >> >cables from >> >> >the TV and see if that changes the severity of the >interference; >> >might give >> >> >you a clue. >> >> > >> >> >If that doesn't seem to improve it, it's probably radiating >> >through the TV's >> >> >plastic chassis. You can experiment with lining the inside of >the >> >cabinet >> >> >with EMI/RFI shielding foil or spray-on shielding products, but >if >> >you have >> >> >to go that far, and with the final results potentially still >not >> >being >> >> >acceptable, the direct solution first proposed above is >probably >> >the best >> >> >way to go... >> >> > >> >> > --- Jeff WN3A >> >> >> > >> > >> >> >> Ron Wright, N9EE >> 727-376-6575 >> MICRO COMPUTER CONCEPTS >> Owner 146.64 repeater Tampa Bay, FL >> No tone, all are welcome. >> > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
