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Old 13-Sep-2014, 5:48 PM   #1
OIIIOThing
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Perplexed by one station-"green" but won't come in.

I need a little advice. I have decided to cut the cord and have begun the process of setting up my OTA system. I am surprised that I cannot readily pull in all the “Green” stations with my current setup. See analytics report here: http://www.tvfool.com/?option=com_wr...d243a2d7151ab7

SITUATION: At this point the greatest challenge I have run into is pulling in WILM RF40. As you can see from the report it is co-located with the PBS station RF29 @ 24 miles away @300 degrees . I am able to get all of the locals except RF40. I think it is because the power is so much less on 40 since it is co-located with 29 and 29 comes in fine. (Looks like about 24dB difference.) The head-scratcher is that I CAN pull in RF34 pretty well and it is transmitting further away (34.9 miles vs 24.1 miles and from a completely different direction (43 degrees). 34 seems to be broadcasting with slightly more power but it seems negligible. For what it is worth, I don’t pull in any signal from the other stations (in yellow) @267 degrees RF22, 26, or 49. They are much lower power but in the same location as my two strongest stations mentioned earlier. Not sure what these stations are as their call signs aren't typical, maybe they are place holders or something. Nor do I pull in RF 43 even though it is in same location as others and in "green" (it may be off the air).

EQUIPMENT: I am using an ANT751 on the roof of my 2 story home (20 ft off the ground). Pointed @ approx 300 degrees. I also have a preamp at the antenna RCA-TVPRAMP1R. There is a 4-way splitter in the system right before going into the house.

I am considering getting a larger antenna but not sure what the best course of action is for my situation. Thanks for any help you can provide.
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Old 13-Sep-2014, 5:55 PM   #2
ADTech
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Move the antenna several feet and try again. Rinse and repeat as needed.

TV signals are often cantankerous and they don't necessarily make themselves appear where we decided an antenna would be convenient. Trees and other obstacles will more likely make the situation more pronounced.

The five character call signs are translators (relays). You can usually look them up at www.rabbitears.info Wilmington is market # 152 on that listing. You can also usually Google the call sign. Be aware that just because there's a license that TVFool has pulled from the FCC's database doesn't mean the station is actually on the air.
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Last edited by ADTech; 14-Sep-2014 at 4:26 PM.
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Old 13-Sep-2014, 10:42 PM   #3
emartz91
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Move the antenna until you find the spot with best signal stregnth. Best bet is above the roof with good los to the stations. If you need a larger antenna, go with the Antennacraft HBU-33.
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Old 14-Sep-2014, 4:11 PM   #4
Ben Myers
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Quote:
Originally Posted by OIIIOThing View Post
I need a little advice. I have decided to cut the cord and have begun the process of setting up my OTA system. I am surprised that I cannot readily pull in all the “Green” stations with my current setup. See analytics report here: http://www.tvfool.com/?option=com_wr...d243a2d7151ab7

SITUATION: At this point the greatest challenge I have run into is pulling in WILM RF40. As you can see from the report it is co-located with the PBS station RF29 @ 24 miles away @300 degrees . I am able to get all of the locals except RF40. I think it is because the power is so much less on 40 since it is co-located with 29 and 29 comes in fine. (Looks like about 24dB difference.) The head-scratcher is that I CAN pull in RF34 pretty well and it is transmitting further away (34.9 miles vs 24.1 miles and from a completely different direction (43 degrees). 34 seems to be broadcasting with slightly more power but it seems negligible. For what it is worth, I don’t pull in any signal from the other stations (in yellow) @267 degrees RF22, 26, or 49. They are much lower power but in the same location as my two strongest stations mentioned earlier. Not sure what these stations are as their call signs aren't typical, maybe they are place holders or something. Nor do I pull in RF 43 even though it is in same location as others and in "green" (it may be off the air).

EQUIPMENT: I am using an ANT751 on the roof of my 2 story home (20 ft off the ground). Pointed @ approx 300 degrees. I also have a preamp at the antenna RCA-TVPRAMP1R. There is a 4-way splitter in the system right before going into the house.

I am considering getting a larger antenna but not sure what the best course of action is for my situation. Thanks for any help you can provide.
Try raising or lowering the antenna. Also, you might try temporarily bypassing the splitter and see if that makes a difference. Possible adjacent channel interference from WTMV, although this isn't supposed to be a big problem with digital.
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Old 14-Sep-2014, 4:25 PM   #5
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Possible adjacent channel interference from WTMV, although this isn't supposed to be a big problem with digital.

Shouldn't be an issue in this case. ACI usually starts to become an issue when the differential in signal power levels goes above 30-35 dB. In this case, the differential is less than 10 dB.
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Old 14-Sep-2014, 8:04 PM   #6
OIIIOThing
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Thanks for all the input. I have experimented with moving the antenna around up/down, side to side, etc as well pointing it different directions. The only real effect I can see is pointing different degree heading. Right at 300 seems to bring in everything but 40. My TV is telling me the signal strength is about -84dB whereas most everything else shows as -69 to 70dB range. I'm getting the feeling I need a bigger antenna to strengthen the signal from that station.

I also did try taking the splitter out of the equation but no big effect.

The HBU33 was recommended...why that one vs another? I know its a good antenna but is there something specific I should be looking for?

Thanks again all.
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Old 14-Sep-2014, 10:24 PM   #7
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My TV is telling me the signal strength is about -84dB whereas most everything else shows as -69 to 70dB range.
You have a TV that tells you that?
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Old 15-Sep-2014, 1:58 PM   #8
OIIIOThing
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You have a TV that tells you that?
Yeah, believe it or not. I was surprised too. I was actually using another "nicer" TV until I stumbled across this on the smallest, cheapest tv we own. It's a Toshiba. It gives a lot of data but I don't know how to interpret most of it.
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Old 15-Sep-2014, 2:11 PM   #9
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That one would be the first I've ever heard of that provided that articular piece of data.

Can you grab the model number and perhaps take and post a photo of the diagnostic screen that shows that?
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Old 15-Sep-2014, 5:44 PM   #10
Stereocraig
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My SNR is in dB, the AGC is in % and signal strength is 0-100 in bars of 5.

The only thing I would find useful about any of them, would be for fine tuning the rotor.

My beef w/ this thing, is that it shuts off, when I change channels.
It also, takes a minimum of 10 clicks, to get to it and there is no shortcut.
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Old 15-Sep-2014, 6:28 PM   #11
Tower Guy
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Originally Posted by OIIIOThing View Post
The HBU33 was recommended...why that one vs another? I know its a good antenna but is there something specific I should be looking for?
Normally, the HBU-33 would work with that TVfool report. Yet, your reception isn't as good as tvfool reports. Add to that the 34 degree difference between your UHF stations. I'd consider a 4 bay UHF antenna. You have two VHF stations that you can try to receive. The HBU-33 would be aimed at WBTW. The 4 bay UHF would require a second VHF antenna Y5-7-13 aimed at WCTI.

If you opt for a second VHF antenna, switch the preamp to the dual input mode.

Double check that the FM trap is switched on in the preamp.
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Old 15-Sep-2014, 9:51 PM   #12
OIIIOThing
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Originally Posted by ADTech View Post
That one would be the first I've ever heard of that provided that articular piece of data.

Can you grab the model number and perhaps take and post a photo of the diagnostic screen that shows that?
Here is a screenshot of the data from the channel I'm struggling with. I don't know that is all that helpful other than as a comparison to other channels and being able to tweak location/direction. At the very least it's interesting.

The model is Toshiba 32HL67.
Attached Images
File Type: png Screenshot_2014-09-15-09-34-02-1.png (379.9 KB, 517 views)
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Old 15-Sep-2014, 10:04 PM   #13
OIIIOThing
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Normally, the HBU-33 would work with that TVfool report. Yet, your reception isn't as good as tvfool reports. Add to that the 34 degree difference between your UHF stations. I'd consider a 4 bay UHF antenna. You have two VHF stations that you can try to receive. The HBU-33 would be aimed at WBTW. The 4 bay UHF would require a second VHF antenna Y5-7-13 aimed at WCTI.

If you opt for a second VHF antenna, switch the preamp to the dual input mode.

Double check that the FM trap is switched on in the preamp.
Thanks Tower Guy. I have actually been thinking of the 4bay type because I thought it might do better at pulling in the weaker signal but also be flexible to pull in frequncies from different directions. My biggest concern is just the "green" stations so anything beyond that would just be icing on the cake.
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Old 16-Sep-2014, 2:02 AM   #14
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I have to say that that is the FIRST TV set I've seen that had a signal power meter like that, a real one!. Too bad its a seven year old model, otherwise, it could become very popular with OTA folks.

There are three particular numbers on that screen that are useful:

1) SNR. ATSV requres a bare minimum of 15.2 dB while 20 dB provides some fade margin. Your screen is reporting it's a bit shy on that station.

2) Signal power. ATSC requires a minimum of around -83 to -85 dBm signal power. Your reading is right on the edge but, with insufficient SNR, it still doesn't work.

3) Uncorrected errors. Ideally, this would be zero when receivable signals are present.

Your task is improve both SNR and signal power. SNR is best improved by getting a stronger signal at the antenna terminals. This can be achieved by installing the antenna in its most favorable available location so that more of the desirable signals can be gathered by the antenna. Moving to a higher gain antenna would also be expected to improve the SNR.

Signal power, after first improving your SNR, can be helped by a modest pre-amp, one selected so as to minimize noise figure, with good overload resistance, and an enough gain to overcome all the downstream insertion losses plus a modest margin. You already have one of those.

Something doesn't compute in your setup and numbers. TVF predicts a signal power of -55 dBm and the 751 has a few dB of real gain on UHF. Let's assume a signal power at the antenna terminal of -50 dBm. The RCA should have around 22 dB of gain and a noise figure around 3 dB on channel 40 according to a sample I tested. Assume 50' of RG6 (-3 dB) and -8 dB insertion loss for a four port splitter. That means that the signal power level at the tuner should be around -40 dBm. You're more than 40 dB short, a very, very, very considerable amount.

That means one of several things: Either the signal power at the antenna isn't as predicted due to obstacles in front of the antenna or you have some excessive losses in the rest of the system.

Are there trees or any buildings in the line of sight to WILM?

Have you verified that the amp actually works?

Have you runs a single, know good length of coax straight from the antenna to that Toshiba?
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Old 16-Sep-2014, 2:55 AM   #15
Tower Guy
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Originally Posted by ADTech View Post
You're more than 40 dB short, a very, very, very considerable amount.
The WILM antenna is side mounted on the tower. Such a mount often causes deep nulls in the transmitted pattern, but usually not 40 db.

The WILM antenna is circularly polarized, which means that there is as much vertically polarized signal as H-pol signal. When side mounted, the nulls caused by the tower are different between H-pol and V-pol. That suggests that twisting your antenna so that the elements are diagonal (45 degrees) may offer a solution that you can try. You'd loose 3 db on signals that are only H-pol and pick up much more than that if there is a V-pol signal in the air at your house.

Last edited by Tower Guy; 16-Sep-2014 at 3:09 AM.
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Old 16-Sep-2014, 3:05 AM   #16
OIIIOThing
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The WILM antenna is side mounted on the tower. Such a mount often causes deep nulls in the transmitted pattern, but usually not 40 the WILM antenna is circularly polarized, which means that there is as much vertically polarized signal than H-pol signal. When side mounted, the nulls caused by the tower are different between H-pol and V-pol. That suggests that twisting your antenna so that the elements are diagonal (45 degrees) may offer a solution that you can try. You'd loose 3 db on signals that are only H-pol and pick up much more than that if there is a V-pol signal in the air at your house.
Ok, what? LOL I'm not well versed in all of the technical jargon for OTA antennas. So if the desired station is at 300 degrees from my location, I should actually point my antenna at 45 degrees from that which would be 255 or 345. Am I following you?
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Old 16-Sep-2014, 3:44 AM   #17
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No, just pretend it's a set of airplane wings and you're in a 45° bank for a turn.

Okay, really need to answer the question about trees or other obstacles as well as the rest of them. I've learned the hard way that trees in front of a UHF signal will drive you crazy, regardless of how close one might be to start with.
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Last edited by ADTech; 16-Sep-2014 at 3:46 AM.
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Old 16-Sep-2014, 1:59 PM   #18
OIIIOThing
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No, just pretend it's a set of airplane wings and you're in a 45° bank for a turn.

Okay, really need to answer the question about trees or other obstacles as well as the rest of them. I've learned the hard way that trees in front of a UHF signal will drive you crazy, regardless of how close one might be to start with.
Yes, we have trees. Lots and lots of trees...in close proximity to the house, in the LOS of the majority of the signals. Which brings me back to my original post. My confusion is why does everything else come in except this station; even other "low powered" signals in totally different directions come in. It seems the trees would keep other signals from coming in too. We live near the water so things are generally flat here.

I completely agree, something doesn't add up. From what I've gathered, I need a higher gain antenna to pull in this lower powered station. Is that the bottom line? What type provides the greatest gain? My goal is the green stations, anything above that is icing on the cake.

Thanks again all.
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Old 16-Sep-2014, 5:51 PM   #19
ADTech
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It's the trees, in my opinion.

I've seen situations "out in the woods" with my spectrum analyzer where signals can vary as much as 20-30 dB on some channels (but not others) just by moving the antenna a few feet. On another occasion, I've been within visual line of sight, excluding trees, of a million watt UHF site here in St Louis, and a single big silver maple tree in full leaf would completely wipe out reception of that station when the antenna was behind the tree and the wind was blowing. Moved a hundred feet off to the side and the signal measured as expected on the analyzer.

Best course of action I've found is the combination of the following:

1) Largest UHF antenna feasible for the situation (might call for a Yagi, 4 bay or 8 bay).
2) Mount the antenna as far back from the trees as possible.
3) Mount the antenna as high as possible.
4) Boresight the antenna to the visual horizon at the treetops.
5) Judicious use of a preamplifier to preserve whatever signal might be at the antenna's terminals.

That's it, short of making firewood out of every tree that's confounding your reception, building an extraordinary tower above the trees, or calling United Van Lines.

I would certainly suggest trying the 4-bay UHF antenna. Your odds will be substantially better. Be very flexible on selecting its mounting location and don;t drill any holes until you're satisfied that reception is as desired. If you have VHF channels on your "must have" list, you may well need to address them separately.
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Last edited by ADTech; 16-Sep-2014 at 5:57 PM.
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