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Thread: KRBK 49 signal issues

  1. #1
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    Jul 2005
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    Default KRBK 49 signal issues

    One of my locals, Fox affiliate KRBK 49 Osage Beach MO, runs a five transmitter setup to maintain their coverage area...
    https://www.rabbitears.info/market.p...n=krbk#station

    Attached is a screen capture of my autologger's (HDHR) graph for KRBK this morning. They actually had a decent signal coming in but I kept moving the antenna to try to correct a signal issue. No matter how strong I got the signal to come in, the problem wouldn't go away. As I write this, their signal strength is right at 90% but they continue to pixelate. I brought the signal bar up on the Zenith converter box and watched it for awhile - the signal was steady and every couple seconds they would hiccup with a bunch of pixels all over the screen and sometimes they acted like they were going to drop out, but the signal was still there and not dropping or bouncing.

    Anyone have any idea what could be going on with KRBK? They are the ONLY station in the Springfield market I have problems with like this. I have talked to others that say they have similar problems with KRBK.

    The closest transmitter to me is in Springfield and is just about 11 miles to the E-SE. In the graph, where the signal jumps, is where I moved the antenna to get the signal to PEAK on that tower.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	KRBK 49 graph 7-23-17 1130.jpg 
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    Jim Thomas
    Springfield, MO

    Ozark Mountain DTV dxing Daredevil

    Dx Equipment - AntennaCraft MXU59 UHF antenna & homebrew version of AntennaCraft Y10-7-13 VHF antenna @ 25'. Both antennas fed through a Winegard HDP-269 12dB pre-amp; a Zenith DTT901 converter box & a Silicon Dust HDHomerun Dual ATSC tuner, using Rabbitears autologger support.

  2. #2
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    Follow up to this. I made another screen capture of KRBK's signal graph, a little after the signal issues were appearing. In this one you can see where I was having signal issues. THEN - it made me wonder IF there was a possibility of some tropo interference going on. So I checked the APRS map, which is attached for the time in question.

    The ONLY station to the east that could *possibly* present a problem is WDKA 49 Paducah KY @ 244 miles. WDKA runs 1000kw, with a 1073' tower. So I suppose that could be the reason for the signal issues. But I didn't confirm that I had any signals coming from Paducah. I have logged WDKA when it was in during intense tropo and overtook KRBK's signal.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	KRBK 49 graph 7-23-17 1245.jpg 
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    Last edited by Jim Thomas; 07-23-2017 at 04:16 PM.
    Jim Thomas
    Springfield, MO

    Ozark Mountain DTV dxing Daredevil

    Dx Equipment - AntennaCraft MXU59 UHF antenna & homebrew version of AntennaCraft Y10-7-13 VHF antenna @ 25'. Both antennas fed through a Winegard HDP-269 12dB pre-amp; a Zenith DTT901 converter box & a Silicon Dust HDHomerun Dual ATSC tuner, using Rabbitears autologger support.

  3. #3
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    Mar 2007
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    Pembroke Pines, FL, USA
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    If I am reading this right, Jim, it might not be QRM at all.

    I once put up an unlisted YouTube of the former RF 21 WGEN---it had maybe 80% signal but audio kept cutting in and out.

    Now today, WLMF 53 (RF 51) does this same thing. I could aim right at the transmitter, and the thing audio/video going on and off. Nobody in their right mind would watch such TV---not even DXers.

    Edit---here you go....is this the issue?

    https://m.youtube.com/watch?v=C22g2GIK2ZE

    cd

  4. #4
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    CD, I can't really say the two are the same. KRBK had pixels (the squares) popping up on the screen and there were audio drop outs, but the signal meter was staying steady. Another nearby TV dxer had KAIT Jonesboro AR come in earlier off the back of his antenna. Jonesboro is in the same general direction and he said he didn't think about checking that direction either. He thinks I was getting WDKA's signal at the time of the interference. I did have a sub-decode signal on RF 12 earlier, which could have been Cape Girardeau MO (which I have logged before). BUT, I didn't even think at the time it could possibly be tropo interference.

    It still doesn't rule out the fact I have signal issues with KRBK, and other viewers do too. KRBK even has a web page on their website about "Having trouble getting KRBK's signal?"
    Jim Thomas
    Springfield, MO

    Ozark Mountain DTV dxing Daredevil

    Dx Equipment - AntennaCraft MXU59 UHF antenna & homebrew version of AntennaCraft Y10-7-13 VHF antenna @ 25'. Both antennas fed through a Winegard HDP-269 12dB pre-amp; a Zenith DTT901 converter box & a Silicon Dust HDHomerun Dual ATSC tuner, using Rabbitears autologger support.

  5. #5
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    Jul 2016
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    Currently DXing In Colbert And Lauderdale Counties In AL, And Alcorn And Tishomingo Counties In MS.
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    If KRBK is broadcasting from 5 transmitters couldn't another transmitter of theirs be causing interference to the transmitter closest to your location? Of course that still uses tropo as the explanation and if there was no tropo then my theory here can't be correct.

  6. #6
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    Springfield, Missouri
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    That is a good point I have always wondered about. What prevents one transmitter from interfering with another that is co-channel? Especially if there is tropo enhancement? I hope one of the TV engineer types on this forum will see this thread and enlighten me. IF that is entirely IMPOSSIBLE, then I would like to know why KRBK has a very unreliable signal. The Springfield transmitter is supposedly 171 kw ERP and I am 11 miles from the transmitter. AND at the same time, I have a co-channel transmitter of the same station to my north (Polk MO) that is 43 kw and I am also inside its contour area.

    Here is the antenna contour for the Springfield tower....
    https://www.rabbitears.info/contour....1495755&site=3

    Here is the antenna contour for the Polk MO tower, which is about 40 miles N-NE of my home. I am on the NW side of Springfield, right where the red line starts to curve back to the NW....
    https://www.rabbitears.info/contour....1495755&site=2

    One of my brother-in-laws lives about 30 miles west of the KRBK tower in Springfield, with his antenna in the attic, pointed directly at their tower. Almost every evening, around 8pm, the KRBK signal drops out for about 2 hours. It doesn't matter what kind of weather it is. He said it is so bad it is unwatchable for about two hours, most evenings.
    Jim Thomas
    Springfield, MO

    Ozark Mountain DTV dxing Daredevil

    Dx Equipment - AntennaCraft MXU59 UHF antenna & homebrew version of AntennaCraft Y10-7-13 VHF antenna @ 25'. Both antennas fed through a Winegard HDP-269 12dB pre-amp; a Zenith DTT901 converter box & a Silicon Dust HDHomerun Dual ATSC tuner, using Rabbitears autologger support.

  7. #7
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    Thunderstorm, KY
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    Fwiw... My most common QRM problem is WBUY 41/40 Holly Springs, MS (140 mi) knocking out local KET tx WKPD 41/29 Paducah, KY (20 mi). It'll start with occasional drop outs / pixilation until it reaches total wipe out. If I want to continue watching KET I have to switch over to WKMU 36/21 Murray / Mayfield, KY (10 mi).

    I, too, have wondered how those multi tx / same channel systems could possibly work w/o QRMing each other.

    73, Ed NN2E
    Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds
    "You Might Be a Redneck If...
    Your TV is on 24/7.
    Your TV has been permanently on for over a decade.
    The only time your TV is off is during a power outage.
    Your TV gets 512 channels, but you go outside to use the bathroom.
    Your new TV is sitting on top of your old TV.
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  8. #8
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    Arizona
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    Quote Originally Posted by NN2E View Post
    Fwiw... My most common QRM problem is WBUY 41/40 Holly Springs, MS (140 mi) knocking out local KET tx WKPD 41/29 Paducah, KY (20 mi). It'll start with occasional drop outs / pixilation until it reaches total wipe out. If I want to continue watching KET I have to switch over to WKMU 36/21 Murray / Mayfield, KY (10 mi).

    I, too, have wondered how those multi tx / same channel systems could possibly work w/o QRMing each other.

    73, Ed NN2E
    Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds
    What is used here is a "slot antenna". KRBK's five are from Jampro.

    Slots are often used to provide SFN services in various digital television systems. The patterns have to be carefully designed and planned out by computer.

    What ATSC 1.0 lacks is the robust error correction that makes SFNs more viable in other systems. For instance, there is the possibility of deploying more SFNs with ATSC 3.0.
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  9. #9
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    Here I go, again...

    Computer modeling is a wonderful thing but, sooner or later, it has to come out of the computer and into the real world. At this point, all bets are off. At ch 49 (680+ MHz) all it takes is a chunk of sheet metal, about 1.5 ft square, to make a nifty reflector. Once the signal hits any such object you can say: "Let the multi-path interference issues begin!"

    Think about all of the metal objects within a station's transmitted footprint (and in your neighborhood)... Cars, trucks, barns, buildings, and let's not forget overhead wires... the list is nearly endless. Throw in a couple of other signals from these multi-tx systems and, well, you see where this is going... A neighbor could park his car in the 'wrong' spot and end up wiping out your, once viewable, DTV signal.

    I've had it happen here... After a storm, my neighbor's barn had some of it's sheet metal roofing come loose and start flapping in the breeze. I lost the ability to watch one of my local UHF DTVs and, I saw wild signal variations / picture break-up on other UHF channels. Once repairs were made to the barn roof, everything went back to normal.

    Really, it's just wishful thinking that multi-tx's can co-exist on the same channel in relatively close proximity. It may look fine on the computer but, in the real world, chaos is inevitable. The exception might be, two tx's in mountain valleys with a 5000 ft peak in between them.

    73, Ed NN2E
    Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds
    "You Might Be a Redneck If...
    Your TV is on 24/7.
    Your TV has been permanently on for over a decade.
    The only time your TV is off is during a power outage.
    Your TV gets 512 channels, but you go outside to use the bathroom.
    Your new TV is sitting on top of your old TV.
    Your TV costs more than all of your other furniture.
    Your deer-stand has a TV antenna on it.
    Your cable provider has no idea that you exist."
    Jeff Foxworthy

  10. #10
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    Pleasant View, TN EM66
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    Fully agreed & that's why we don't have many single-frequency networks (SFNs) in the USA. ATSC-1 isn't very well suited for them. There is a single modulated carrier, and if it suffers any interference (even from another transmitter broadcasting the same program) it's toast. As Raymie says, you have to use computer modeling to try to put the interference areas in places where no large audience lives. If you're a *small* audience (like Ed!) you're out of luck...

    ATSC-3 will probably be better at this. It uses multiple carriers (thousands of them). The chances that any one (or two, or fifty) will suffer interference are fairly high. The chances that *most* of them will suffer interference are fairly low. In a SFN, it is even (very) possible carriers from one site will fill in carriers lost from another site -- receiving two or more SFN sites simultaneously can *improve* reception.

    The downside is higher peak-to-average power ratio. Which means for the same *average* power (and coverage) the voltages are higher. To keep things from arcing over you need physically larger (and more expensive) RF components -- antenna, feedline, filters, etc...
    Doug Smith W9WI
    Pleasant View, TN EM66
    http://www.w9wi.com

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