adjacent channel interference

[olimazi]

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.

[JoeAZ]

From your report, it would be WNJT which broadcasts PBS
on RF 43. That is one of your strongest signals.

[rabbit73]

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.



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

[olimazi]

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.

[rabbit73]

could not find a date for when that's happening...

The changes will happen very slowly over the next 3 to 3-1/2 years. New antennas have to be mounted on all the transmitter towers that are changing channels. There aren't many companies that do antenna tower work; they will be very busy. You will need to do a channel scan often to keep up with the changes.

https://www.fcc.gov/about-fcc/fcc-in...ion-transition

http://www.tvtechnology.com/news/000...gnments/280840

A total of 987 TV stations will be moved in the upcoming 39-month repack, and 175 broadcasters who sold spectrum in the auction will split the $10 billion offered up for it by wireless providers.

“The first group of stations to move channels is scheduled for Nov. 30, 2018,” the release said. Those stations now have 18 months to move.

Repack Deadlines:

https://www.commlawcenter.com/2017/0...deadlines.html

[ADTech]

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.

[olimazi]

so how do I notch it, heh

Originally Posted by ADTech

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.

[rabbit73]

Originally Posted by ADTech

Since WJNT sold out in the auction, their usage of channel 43 will cease pretty much as soon as they get paid.

It's WNJT, not WJNT. I'm from NJ, so it caught my attention.

When will they get paid?

[rabbit73]

Originally Posted by olimazi

so how do I notch it, heh

Not easily done.

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.

[olimazi]

Originally Posted by rabbit73

Not easily done.

A DIY coax stub or a simple LC filter between the two channels,

I'm willing to try the lc filter, can you guide me in the right direction.
Do I need the exact frequency of the station, 4368007 I believe.

[ADTech]

Originally Posted by rabbit73

It's WNJT, not WJNT. I'm from NJ, so it caught my attention.

When will they get paid?

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.

[rabbit73]

Originally Posted by olimazi

I'm willing to try the lc filter, can you guide me in the right direction.
Do I need the exact frequency of the station, 4368007 I believe.

I will try. Channel 43 for WNJT is 644 to 650 MHz; channel 44 for WNYW is 650 to 656 MHz. The pilot carrier for WNYW is near the low end of the channel at 650.31 MHz, which is used by the tuner to lock on to the WNYW signal.

The challenge is to make the channel 43 signal weaker without doing harm to the channel 44 pilot.



Fortunately, the signal doesn't use the whole width of the 6 MHz channel.



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:





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.

[ADTech]

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.

[rabbit73]

Originally Posted by ADTech

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.

I agree.

My suggest is to wait until the local station goes off the air as that will resolve the problem until the desired stations move.

Even then, with WNJT off the air, you might still have a problem with WNYW because of the big tree in front of your Winegard HD7698P antenna.