Recommendations - OTA pre-amp?

Discussion in 'TiVo Premiere DVRs' started by rsisters, Nov 12, 2011.

  1. rsisters

    rsisters New Member

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    May 21, 2005
    Thanks to the TC we made the leap from $atellite to OTA and Hulu (soon to branch out to Netflix). So far, we're lovin' it...except for one station.

    At first our local NBC station reception was great. But in the past month it has gone crazy! The signal fades in and out constantly - which is really annoying especially during Sunday Night Football and a handful of other shows not available via Hulu and Netflix :mad: We have researched - confirmed - tested - aligned - realigned the outdoor antenna but nothing seems to make this station reception any better. We are using a ClearStream4 HD Antenna.

    Should we try a pre-amp? I am very confused about the specifications of pre-amps that I see. Does anyone have a brand or model recommendation?

    Thanks in advance for the TC help!
     
  2. timatkn

    timatkn New Member

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    Oct 1, 2010
  3. phone man

    phone man Member

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    Nov 4, 2011
    A preamp can sometimes make things worse. Especially if it's too strong or has a high noise figure. It would help if we knew more about your particular OTA setup. Going to TVfool.com is a good place to start.
    Go http://www.tvfool.com/index.php?option=com_wrapper&Itemid=29 here and fill in your address and antenna height.
    Also tell us how many TVs you're using OTA, how many and what type splitters, the distance from the antenna to the farthest TV and whether your antenna is outside or in the attic.
     
  4. aaronwt

    aaronwt UHD Addict

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    Northern...
    I've been using a Winegard pre-amp for 7.5 years now. It's still outside working great. But in my situation I had problems getting all my channels reliably.
    I first got one with about 15dB gain but that didn't help enough. SO then I got one with around 30dB gain which worked great in my situation. I didn't want to get that initially since I wasn't sure if it would over power the signal but in my situation it worked great.

    But since the Op only has a n issue with one channel, and it only recently caused issues, it might be from the changes in the foilage on the trees. in my area in November this affects one channel I have to the point that it's not as a reliable signal. But it also is better now than in the past few years since the trees have grown.
     
  5. unitron

    unitron Well-Known Member

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    Which is what happens when you use UHF for TV stations instead of VHF. Where a lower frequency signal would "wrap around" an obstacle and keep going, a higher frequency one get's stopped dead in it's tracks. And of course the old analog signals degraded gracefully.
     
  6. rsisters

    rsisters New Member

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    May 21, 2005
    Thanks for all the suggestions. Learning that pre-amps can make reception worse is something that we hadn't thought of.

    We are OTA with two HDTV (Panasonic Plasmas - internet built-in) each w/Premiers. The outdoor ChannelMaster4 antenna is 10-12' from TV#1 and about 20-22' from TV#1. There are no splitters being used as we had separate coax leads from a past satellite that we utilized when we hooked up the OTA.

    We are the highest roof in the 'hood - very few obstacles for about a 1/2 mile. No trees (we're in the desert). No - airplanes (we live near a National Guard helo pad, surrounded by protected park land). All the major local station antennas are on top of the same mountain.

    What I don't get it that the reception is poor on only one channel. This channel came in great and has only recently gotten unstable. Could it be something on the station's end?
     
  7. L David Matheny

    L David Matheny Active Member

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    Jan 29, 2011
    SE Ohio
    A pre-amp can cause overload on stations that are nearby.

    I searched for "ChannelMaster4" antenna and came up empty. I think you said earlier that you have a "ClearStream4" antenna, which is a UHF model made by Antennas Direct. You've also said you're in 85257. If your NBC station is KPNX-DT, it's on RF channel 12, which is high VHF. A UHF antenna won't receive that as well as it receives the UHF channels it's optimized for. I have no idea why it originally came in better.
     
  8. phone man

    phone man Member

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    Nov 4, 2011
    You have two TVs and one antenna. The signal is being divided somewhere. Please verify what kind of device is doing this. It should be a simple 2 way splitter. Are there any unused TV locations or coax wiring in your house left over from the satellite setup?
    Yes, the Clearstream 4 is UHF only and may be having difficulty with a VHF channel. Posting the results of the TV fool report here would help.
     
  9. phone man

    phone man Member

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    Nov 4, 2011
    rsisters, Here's the report based on your zip code only. A report for your exact address might be slightly different.

    http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=ec129cca0e8bc9

    With 2 TVs, short coax runs, and excellent signal strength, you should have no problem getting lots of channels. I wish my report looked this good! You do not need an amplifier of any kind. The clearstream 4 might be overkill as well. A smaller UHF/VHF combo antenna would have done the job easily.

    You can see that KAET (real ch 8), and KPNX ( real ch 12) are VHF.
     
  10. unitron

    unitron Well-Known Member

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    semi-coastal NC
    Depending on how he defines "recently", is it possible that the station to which he refers was simulcasting on its old VHF analog allocation and digitally on a UHF allocation, and then when NTSC got shut down went to digital on its original VHF frequency?
     
  11. rsisters

    rsisters New Member

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    May 21, 2005
    Thanks to everyone who weighed in on my original post. Last night we Tivo'ed the Sunday night game on NBC - and the reception was perfect!

    That got me researching KPNX Channel 12. I discovered that Channel 12 and the ABC stations have been making transmission changes that primarily affect towns in the high country (Flagstaff, Prescott, etc) over the past few weeks. Several websites noted that during these transitions some area might not have access to the station for 24-48 hours. Not that I understand all the scientific details but it might explain the sudden change.

    Thanks again everyone - Tivo people - rock!
     
  12. rsisters

    rsisters New Member

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    May 21, 2005
    Thanks for your posts - when "shopping" for antenna we were torn between too much antenna and not enough antenna. After getting several great recommendations from the TC - we went with the "4". We were also looking towards the future as we hope not to be in AZ much longer.

    One trick we have learned - the separate cables (from the old satellite set-up) was a bonus in the antenna set-up. We lucked up :D
     
  13. aaroncgi

    aaroncgi New Member

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    Apr 13, 2010
    I think the foliage is what's affecting our signal on a couple stations. I initially went with a Winegard HDP-269 as signal strength was pretty high on most stations with no preamp and we didn't want to overload on those. Basically I just wanted to overcome any line or insertion losses, though I was hoping it would beef up signal strength on the few stations that were marginal. Unfortunately, I installed it in the good part of the year - mid spring. It's exactly at this time that signal strength goes up significantly on the weaker stations. Come November though, once the leaves have fallen off the trees, the weaker stations are once again marginal, even with the preamp (though strength is generally higher than with no preamp). So the HDP-269 isn't cutting it for us. I just ordered the AP-8700 which has 5-7 dB more gain, so hopefully that will do the trick. I could go up to the AP-8275 but that's a whopping 16-17 dB more, seems extreme.

    Our TV fool report is pretty grim though, so we'll see. This time I'll make sure to install the AP-8700 immediately, so I can return it for the AP-8275 if not satisfactory. I should know tomorrow. :)

    Oh and based on the TV Fool report for the original poster, there should be no need whatsoever for a preamp. An indoor antenna would probably do the trick. Any outdoor antenna will be in heaven with that kind of view and distance.

    For a real challenge, here's ours:

    http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=ec12a9eb64d0e2
     
  14. phone man

    phone man Member

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    Nov 4, 2011
    What antenna are you using and which way is it aimed? How much line loss are you trying to overcome?
    Your report looks a lot like mine though most of the stations I wanted to receive are in the same general direction and only 10 degrees apart.
    http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=3e47e33abc7580
    A friend who does sat tv and antenna installation recommended the CM 4228HD since it covers high VHF and UHF. It's aimed SSW. Fortunately, the only other channel I wanted to pickup (WMFD, real ch 12) is in the opposite direction and strong enough to be picked up by the back side of the antenna.
    I added a preamp to help with a 110' coax run to the bedroom and also to help pull in a weak channel (WWHO) that was 65 miles away. The Antenna Direct CPA-19 preamp was recommended and does the job quite well. It's rated at 17.3 dB gain and a low 2dB noise figure. According to the mfg it's also very resistant to overloading. You might want to email Antennas Direct tech support with a link to your TVfool report and see what they say. They were very quick to reply when I had questions about the CPA-19
     
  15. aaroncgi

    aaroncgi New Member

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    Apr 13, 2010
    Thanks for all the tips.

    We have the ChannelMaster 4228 about 10' above the peak of our roof. It's the original CM4228, not the new 4228HD. It's aimed directly at the largest group of stations, approximately 345 degrees. There's only one station we want that's in a different direction (33, at 26 degrees), and it still comes in fine. The problem stations for us are all at the same heading and distance as the main group.

    Our line loss is minimal, consisting of about 75' RG6 cable, a wall plate coupler (figure 0.5dB) and no splitters. So worst case maybe 6 dB of loss in the line? However, the HDP-269 only has 12dB of gain, and around 3dB noise, so you can see it's not helping a lot.

    After trying the AP-8700 yesterday (17-19dB gain), we're stepping up to the AP-8275 (28-29dB gain). The AP-8700 did boost our signal strength per the Tivo, but we only went up between 5 and 9 points on the signal strength figure, which still puts us nowhere near 100 for most channels. The highest was 87, with most still below 80. It was enough boost to make the marginal channels stable, but only just. And oddly, a couple of the channels went down 5 points, though these weren't the marginal ones, so they were still stable. So I think we have little chance of overload with the AP-8275. We should have that within another week or so.
     
  16. phone man

    phone man Member

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    Nov 4, 2011

    I really don't think you need more gain, at least not from a preamp. When you use a preamp, balun loss, loss from the coax between the preamp and the antenna, and the preamps noise figure are the only things that take away from the antenna gain. A preamp with a lower noise figure is what's going to help capture weak signals by preserving your antennas gain and by lowering the ATSC tuner's noise figure. A preamps gain only has to overcome line loss. More gain isn't better. Use the signal to noise figures on the DVR diagnostics screen instead of the signal strength meter. A steady SNR of twenty and above is all you need for reliable reception. Until it falls below 16 dB, the PQ is the same.
     
  17. aaroncgi

    aaroncgi New Member

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    Apr 13, 2010
    I don't doubt that we in theory shouldn't need more gain than an AP-8700. I think the HDP-269 at 12dB is just barely covering line loss, balun loss, and it's own 3dB noise figure. I have no doubt that a low noise preamp would be better. However, low noise preamps are uber expensive compared to the normal Winegard/Channelmaster units in the 3.0 dB noise range. We're not willing to fork out twice the price for something like the CPA-19 for that extra 1dB less noise.

    So all that said, I did receive and install the AP-8275 last weekend. It did change our CBS station (real CH 39) from unwatchable to stable and has not had problems since. All the other channels signal levels went up as well, but no overload problems at all.

    Honestly I have to wonder if there's some kind of cellular or ham radio operating in the neighborhood that interferes with our signal. Some channels show signs of strong multipath at random times - ie signal strength and SNR will drop from stable to nothing and bounce back and forth every few seconds. It might last a few minutes or all day, but only on certain channels. Usually the next day it's fine. It seems to have no relationship with weather conditions or time of day, though it does seem to plague the VHF channels more often than UHF. I would think if it were from radio stations it would be all the time, not so random and intermittent.
     
  18. aaronwt

    aaronwt UHD Addict

    23,176
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    Jan 31, 2002
    Northern...
    That sounds like what happens here when the leaves have fallen off the trees. There is one channel I receive that is rock solid with a signal level of 30 when the leaves are on the trees. But when teh leaves fall teh signal will bounce all over the place.

    Of course the channel had the best reception when it was on UHF, but when it moved to VHF it had the worst reception of the channels I receive.

    At least it's not as bad as it used to be years ago, since the trees have grown.
     
  19. L David Matheny

    L David Matheny Active Member

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    Jan 29, 2011
    SE Ohio
    I'm no expert, but I think you can see that sort of thing as a result of multipath reflections from passing trucks, trains and maybe even cars and planes. Do any of those things pass near you?
     
  20. unitron

    unitron Well-Known Member

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    Apr 28, 2006
    semi-coastal NC
    If more leaves = better reception, then either the signal is bouncing off of them to get to you or they block some sort of interference that would get through otherwise.

    I have to wonder if there isn't something else going on that just happens to con-incide with the foliage change.


    And generally the lower the frequency the more a signal can wrap around a tree and keep going and the higher the frequency the more likely it is that the tree will stop it dead in its tracks, kinda like how subwoofers appear more non-directional than tweeters.
     

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