adjacent channel interference
tv fool report
http://www.tvfool.com/?option=com_wr...e6a46a9da6d8f6 ch 44 (5.1) FOX from NYC (70 degrees) has an adjacent channel warning; this happens to be my weakest channel, which is the adjacent channel that is giving me trouble? hard to tell from the report; thanks guys, if I can figure out which one it is maybe I can use a notch filter on that frequency to knock it down. |
From your report, it would be WNJT which broadcasts PBS
on RF 43. That is one of your strongest signals. |
A good tuner should be capable of rejecting adjacent channel interference that is up to 33 dB stronger than the weaker desired signal. WNJT is 33.1 dB stronger than WNYT; close call. What helps is that WNJT is in a different direction, so if your antenna is aimed at WNYT, that should make WNJT weaker.
ATSC Recommended Practice: Receiver Performance Guidelines Document A/74:2010, 7 April 2010 RECEIVER PERFORMANCE GUIDELINES 5.4.2 Adjacent Channel Rejection The receiver should meet or exceed the thresholds given in Table 5.2 for rejection of first adjacent-channel interference at the desired signal levels shown above the columns therein. https://forum.tvfool.com/attachment....8&d=1434754883 WNJT will be moving to channel 23 on a sharing basis after "repack": http://www.rabbitears.info/market.ph...&callsign=wnjt WNYW on 44 will be moving to 27: http://www.rabbitears.info/market.ph...&callsign=wnyw WTXF on 42 will be moving to 31: http://www.rabbitears.info/market.ph...&callsign=wtxf |
adjacent channel interference
thanks joe,
rabbit, my tuner is on the tivo bolt, from my research it is a very good one (far superior to the one in my samsung tv, I've tested it). so I should not bother trying to filter ch 43 out since the channel frequencies will change soon with the repack, eh? could not find a date for when that's happening... btw, ch43 is coming in strong, even from the side of my antenna - stronger than most of my channels. |
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https://www.fcc.gov/about-fcc/fcc-in...ion-transition http://www.tvtechnology.com/news/000...gnments/280840 Quote:
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https://www.commlawcenter.com/2017/0...deadlines.html |
WNYW and WTXF are both moving during summer of '19, phase 4.
Since WJNT sold out in the auction, their usage of channel 43 will cease pretty much as soon as they get paid. Their programming will move to a shared arrangement on WJNT's station. |
yikes
so how do I notch it, heh
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When will they get paid? |
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A DIY coax stub or a simple LC filter between the two channels, at the upper end of 43 might not be sharp enough. A custom adjacent channel filter from Tin Lee Electronics would be expensive and it would make WNYW a few dB weaker. I'm not convinced it needs to be notched, because WNJT is in a different direction, making it weaker. I think the tree in front of your antenna is really the problem for WNYW. |
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Do I need the exact frequency of the station, 4368007 I believe. |
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Typo on my part. The description and information is correct though. Soon. Depends on when the checks from the winning wireless bidders come in. Then, stations who are going off the air completely have 90 days to do so while stations who will channel share have 180 days to relinquish their pre-auction channel once that have been paid. |
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The challenge is to make the channel 43 signal weaker without doing harm to the channel 44 pilot. http://forum.tvfool.com/attachment.p...1&d=1499630608 Fortunately, the signal doesn't use the whole width of the 6 MHz channel. http://forum.tvfool.com/attachment.p...1&d=1499631570 A simple LC filter would consist of an inductor (coil) and a variable capacitor in series connected between the center conductor of the coax and the shield (ground). A notch filter looks like this: http://forum.tvfool.com/attachment.p...1&d=1499647114 http://forum.tvfool.com/attachment.p...1&d=1499647313 That type of filter would probably attenuate one FM channel, but I doubt that it would do what you want to make channel 43 weak enough to avoid harming channel 44. |
A "brick wall" filter would be required to attenuate an adjacent channel by that magnitude. Frankly, unless you're willing to spend thousands of dollars on an experiment, it isn't going to happen. Trying to have a 30+ db roll-off in a vary narrow span of less than a couple of hundred kHz just isn't going to happen without a LOT of LC pairs.
My suggest is to wait until the local station goes off the air as that will resolve the problem until the desired stations move. |
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