The Official AVS Antenna and Related Hardware Topic! - Page 490 - AVS Forum
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Old 03-31-2012, 02:08 PM
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Originally Posted by Mister B View Post

Still I get occasional pixelation on KCOS and KVIA (both the RF7 or RF17 versions). The signal quality and SNR figure is constantly on the move for these channels although the SNR does not fall below about 21 at any time. I have read that fluctuating SNR's may be a sign of multipath reception, but the Juarez analogs do not show hardly any "ghost" at all.

I looked at your TVFool results and your stations are close, LOS and very strong. Are you looking through trees? If you have true LOS to the transmitters it's essentially impossible to have the SNRs jump around. They should all be 30 dB plus. The only time I've seen this sort of behavior is when trees were messing up the signal.

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I have heard that the SNR is determined by the amp and hope that a very high quality amp such as one of the Kitztech's would help.

Yes, the system noise figure is determined by the first amplifier. It's possible to approach the noise figure of the preamp if all the losses after the preamp plus about 8 dB is equal to or less than the preamp gain. There's a formula to calculate overall noise figure.

That said, it's no surprise that the HDP 269 didn't do anything. Signal strength isn't your problem.

I'm not sure I would call the Kitztech a "high quality" amplifier. It has a very low noise figure but it achieves that by not using any input filtering. Most other preamps use input filtering to reduce the chances for unwanted signals to overload the preamp. Filters are not zero insertion loss. You would need to carefully evaluate your situation before using the Kitztech.

I recently replaced a Winegard AP8700 with a Kitztech on my VHF antennas. The 8700 was a bit low on gain in my situation. I live in a rural area with no strong high VHF stations or FM stations or other transmitters below 174 MHz. I felt I could get away with a preamp with no filters other than the filtering affect of the antennas themselves. Between the higher gain and the lower noise figure of the Kitztech, I calculated that I picked up at least 3 dB in SNR. The result was that my weakest station (CH 7 110 miles distant) went from about 75% reception to 90% reception, an improvement but no miracle. No change was seen on any of my stronger stations.

Chuck
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Old 03-31-2012, 03:56 PM
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Thanks for all of the input. I guess I have tried most of the usual suspects in this situation. If I get too far off axis I loose RF 17 and even the RF 7 counterpart, which TV Fool is not showing. KVIA plans to move from 7 to 17 but have been running both for about two years.
I tried 6db attenuators up to three of them equalling 18db, of course lost several stations at that point.
Yes, there are trees! There is a row of pine trees about 100 feet from the antenna, which it must "look through". However, they are rather thin, under-irrigated West Texas trees and I have the antenna in a position that best looks through them. They have not changed much in the 12 years I have lived here which would include the pre-digital era and my first HD set top box (a Samsung SIR-165).
And, no, unfortunately I can not cut them down. They are meant to shield the trailer park from some of the strong westerly winds.
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Old 03-31-2012, 04:13 PM
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You may need more antenna if all of the above suggestions have been tried & didn't help. The slightly larger Winegard 7694 or Antennacraft HBU-33 will offer an improvement in signal gain for both UHF & VHF & also help reduce multipath. Those pine trees must be attenuating the signals quite a bit before they are reaching the antenna.
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Old 03-31-2012, 05:18 PM
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Quote:
Originally Posted by Digital Rules View Post

You may need more antenna if all of the above suggestions have been tried & didn't help.

I am sorry to keep rejecting all of these well meaning and helpful suggestions, but I have already tried my old Winegard 4400 for UHF and YA-1713 for VHF-HI both separately and combined with a UVSJ. No real difference.
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Old 03-31-2012, 05:58 PM
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Quote:
Originally Posted by Mister B View Post

I am sorry to keep rejecting all of these well meaning and helpful suggestions, but I have already tried my old Winegard 4400 for UHF and YA-1713 for VHF-HI both separately and combined with a UVSJ. No real difference.

What is an RCA 721? A Google search doesn't return anything useful except your post.

If you put 18 dB of attenuation in line and lost some stations then I think there is something else going on. TVFool is saying you have noise margins of 55 dB and that makes sense at your distance LOS. You should easily be able to add that amount of attenuation and have nothing happen. The fact that your noise margins are that low is pointing to some unrecognized problem.

I looked up KVIA and KCOS and I see they're both high VHF stations. Problems on VHF and not UHF? That alone is a little suspicious. Trees are rarely a problem on VHF, especially the type you describe.

Chuck
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Old 03-31-2012, 07:49 PM
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Quote:
Originally Posted by Mister B View Post

I am sorry to keep rejecting all of these well meaning and helpful suggestions, but I have already tried my old Winegard 4400 for UHF and YA-1713 for VHF-HI both separately and combined with a UVSJ. No real difference.

According to your TVFool location and the fact that you are looking almost due west (266 deg.), you are looking directly at the El Paso International airport. Airplanes taking off and landing will most certainly create reflections that look like multipath thereby causing pixelation. I don't know of anyway to mitigate that. Perhaps someone else knows.
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Old 03-31-2012, 08:38 PM
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Quote:
Originally Posted by Calaveras View Post

What is an RCA 721?

RCA ANT751 (made by Winegard).
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Old 04-01-2012, 03:03 AM
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At over 50 NM, you don't need any preamp. The problem lies elsewhere.

Have you tried simple indoor antennas ?
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Old 04-01-2012, 03:12 AM
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Quote:
Originally Posted by Mister B View Post

I am sorry to keep rejecting all of these well meaning and helpful suggestions, but I have already tried my old Winegard 4400 for UHF and YA-1713 for VHF-HI both separately and combined with a UVSJ. No real difference.

There may not be anything significant that you can do. I'm not certain that the problem isn't from the stations themselves. I was in El Paso in February, and attempted to get transport stream reads on the stations there. I don't recall having problems with KCOS, but KVIA was a bear, moreso on ch 7, but on ch 17 also. I got reads on most stations from near the junction of Paisano and Montana, but KVIA was a problem. I then attempted to read KVIA from about 1/2 mile west of the junction of Montana and Loop 375. KVIA's signal was all over the place at both locations, on both frequencies, but was better near Loop 375 than further in.

The El Paso HDTV thread often has tales of woe receiving local digital stations.
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Old 04-01-2012, 07:40 AM
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Sorry for the typo on the RCA 751. I live in an aluminum mobile home with a steel roof, so an indoor antenna is not at all feasible.
TV Fool is not entirely correct for El Paso. As I alluded to above, KVIA is in the process of moving from RF 7 to RF 17. 17 was the pre-transition frequency and was quite reliable after they got beyond the 1 KW start-up phase. Both 7 and 17 have been available for at least two years now and at least in my location 17 is much weaker. RF 7 shows a signal quality on the Tivo of about 74 and SNR around 26, but it continually fluctuates like KCOS does. RF 17 has a signal quality of about 48 and SNR of 22, but is very steady. Last night I switched to the 17 version of KVIA and made it through both the ABC and local news without any break-ups.
KTSM is also switching from RF 9 to RF 16, again their pre-transition frequency. Tivo thinks that KTSM is only available on 16, and although I could scan in the RF 9 version I have not as their would be no guide data and recordings would have to be manual. Besides, I figure as they are going to the RF 16 permanently, I may as well use it. That said channel 16 also fluctuates continously, but with SNR's in the range of 24 to 31 I have never seen a problem with that signal.
I too am thinking that this is primarily a VHF problem, in that the worst offenders are RF 7 and 13. The channel 17 signal is just weak, they may not be operating at the power indicated by TV Fool. I will continue to hope for better results on 17 for KVIA however. As for my PBS, of which I am a member and long time supporter, I may have to look into the possibility of bring in KRWG from Las Cruces. I have received channel 23 before, but have not made much effort since they went digital. That would be another project for another day.
In the final conclusion, it is very disappointing that Tivo put such a poor OTA tuner in what otherwise seems to be a very good DVR. I realize there are challenges to my reception location, but I have no problems with my six year old Sony KDF-37H100, nor do my neighbors who have a "Polaroid" flat screen and an old Radio Shack VU-90 antenna that I gave them.
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Old 04-01-2012, 08:25 AM
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If both channel 16 and channel 17 are on the air, you may have adjacent channel interference that your tivo tuners just can't deal with.

Re your Sony and Polaroid TVs: Sony has had excellent OTA ATSC tuners for years. And IIRC, some Polaroid TVs have used LG tuner chipsets, which would explain the superior OTA performance of the neighbor's Polaroid set.

Just for the hell of it, have you tried your Tivo in the room where your Sony is located, connecting it to that coax?
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Old 04-01-2012, 09:30 AM
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I don't know that there is much else we can do to help you short of someone going to your place with a spectrum analyzer. We're all just taking guesses.

Maybe your TiVo is bad. I've read lots of comments from TiVo owners who use them OTA and they all seem to love them. If the tuner was that bad then everyone would hate them. If your old Sony works fine then maybe it is just a bad TiVo unit.

At 18 miles LOS from your transmitters power shouldn't make any difference. I have a transmitter site 14 miles LOS from here with stations on 3, 18 and 28. Channel 28 has just 300 watts in my direction and it gives me a noise margin of 40 dB. Channel 18 has 58 KW in my direction and a noise margin of 65 dB (too strong). I've measured these on a spectrum analyzer. Channel 3 has 30 watts in my direction and my Sony TV gives an SNR of 25 dB using an FM antenna.

The ideas that your stations are too weak, the tuner is too poor, airplanes are breaking up the signal, trees are in the way, etc., don't make any sense in your situation.

BTW, I see XEPM and XEJ listed in your TVFool report. I received both those stations last summer during Es events. XEPM was especially strong. I took a shot of the TV. Image attached. Mountain Ranch is in the Sierra Nevada foothills.

Chuck
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Old 04-01-2012, 10:00 AM
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Quote:


In the final conclusion, it is very disappointing that Tivo put such a poor OTA tuner in what otherwise seems to be a very good DVR. I realize there are challenges to my reception location, but I have no problems with my six year old Sony KDF-37H100, nor do my neighbors who have a "Polaroid" flat screen and an old Radio Shack VU-90 antenna that I gave them.

Maybe your individual Tivo tuner is so poor and out of spec you should consider it defective. It should have a warranty, so RMA and try another unit.

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I live in an aluminum mobile home with a steel roof, so an indoor antenna is not at all feasible.

That could be a source of the multipath reflections, so you could try moving the mast to various places around the yard.

Quote:


I don't know of anyway to mitigate that. Perhaps someone else knows.

Vertically stacking of identical antennas will decrease the effects from airplane fluctuations (but wont completely eliminate). A vertical stack with its narrower vertical beam should also help reduce multipath reflections in a mobile home park.
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Old 04-01-2012, 11:31 AM
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The TiVo tuner is not as sensitive as most built in TV tuners, as I have compared to my Samsung using same antenna set up. It may have to do with the error correction aspect of the tuner in dealing with weak or marginal signals, or multipath. My TiVo will receive relatively strong signals at 70 miles, but there are a few closer range signals that it will not lock onto as well as the Samsung. I think it's more of a signal quality issue rather than signal strength, and if the signal quality is not that good, then the TiVo has difficulty decoding it. Unlike the Samsung.
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Old 04-01-2012, 12:02 PM
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tylerSC,
I have also heard that the Tivo sometimes does not deal with multipath very well.
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Old 04-01-2012, 12:24 PM
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I poked around a little to see what I could dig up on the TiVo OTA tuner. There's the usual confusion between signal quality and signal strength but my take is that the TiVo (HD and Premiere) don't handle multipath very well. One discussion is here:

http://www.tivocommunity.com/tivo-vb...d.php?t=446075

One person notes that the TiVo uses the Microtune MT2131 chip set. That's interesting because my DTVPal DVR uses the same chip set and its multipath handling is identical to my Sony TV and the MyGoTV portable I have. I have major multipath issues here and any tuner less than the best is unusable. My Dish Network VIP-622 has a tuner with poor multipath handling and I can't use it.

The description of the SNR continually jumping around sounds like the equalizer is hunting around for the best setting and never settles on one. You wouldn't want it doing that because you'd lose the picture every time it tried a new setting. Sometimes when my Sony tunes to a channel it'll produce a picture and then retune and put the picture back up. If I watch the diagnostic screen when that happens I see a different SNR displayed on the 2nd tuning, usually better.

I can only speculate, but perhaps the firmware in the TiVo is having a problem in some situations settling on an equalizer setting. Other devices are using the same chips without this problem.

I hope my DTVPal DVR never breaks because it sounds like the TiVo would not work for me.

Chuck
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Old 04-01-2012, 01:47 PM
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I had not seen this before and it might be of interest to some.

http://www.fcc.gov/oet/info/document...on-testing.doc

The FCC tested a bunch of DTVs and STBs back in 2008 for sensitivity in a no multipath environment and separate tests for multipath. Sensitivity was mostly in a narrow range except on low VHF but the multipath tests were all over the place. Multipath tests were not quantitative but consisted of 47 recordings of OTA signals at different locations around New York and Washington and then played back in a loop to the DTVs and STBs in the lab.

It would be nice to have a modern version of this test with the DTV models identified.

Chuck
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Old 04-01-2012, 02:33 PM
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Well, with the current FCC attitude, it'll probably be a cold day in August before you see such a test. It seems they would like for OTA to just go away, so they can transfer all the spectrum to their buddies in the wireless smartphone world.
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Old 04-01-2012, 03:21 PM
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Quote:
Originally Posted by Calaveras View Post

I had not seen this before and it might be of interest to some.

http://www.fcc.gov/oet/info/document...on-testing.doc

The FCC tested a bunch of DTVs and STBs back in 2008 for sensitivity in a no multipath environment and separate tests for multipath. Sensitivity was mostly in a narrow range except on low VHF but the multipath tests were all over the place. Multipath tests were not quantitative but consisted of 47 recordings of OTA signals at different locations around New York and Washington and then played back in a loop to the DTVs and STBs in the lab.

It would be nice to have a modern version of this test with the DTV models identified.

Chuck

Are you suggesting the FCC should act in some way as a Public Servant?
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Old 04-01-2012, 03:44 PM
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I didn't mean to imply that the FCC has to or should do it. There are many ways it could be done. I could do a reasonable job at it here with just my spectrum analyzer, my step attenuator and my many OTA multipath signals if I could borrow a bunch of TVs.

Chuck
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Old 04-01-2012, 04:48 PM
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Quote:
Originally Posted by Calaveras View Post

I didn't mean to imply that the FCC has to or should do it. There are many ways it could be done. I could do a reasonable job at it here with just my spectrum analyzer, my step attenuator and my many OTA multipath signals if I could borrow a bunch of TVs.

Chuck

Thank you. My question was intended as irony. I am not surprised that the FCC is not thought of as Public Servant that might perform the office you suggested. I agree this might not be a job for the FCC, unless the FCC saw a public interest in OTA television.
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Old 04-02-2012, 07:18 AM
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Are you suggesting the FCC should act in some way as a Public Servant?

Yep. To protect and serve us TV 24 hours a day
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Old 04-02-2012, 08:31 AM
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Originally Posted by arxaw View Post

Using the ANT751, what is the weakest channel (lowest on your TVFool report) that you can reliably receive now?

TV Fool Report

Hi arxaw,

The weakest channel that I can reliably receive is:

WEDH-DT (Digital)
Channel: 45
Network: PBS
Maximum ERP: 490.000 kW
Coordinates: 41.703711 -72.832044

There are several stations that are just a little too weak but can be received on odd days and or if I adjust everything to receive TV. For example, turning off my computer and wireless modem/router and pointing the antenna at their tower will lock in reception of:
WFSB (Digital) Channel: 33 Network: CBS

And it sometimes will work with these stations although with an obvious decrease of reliability:
WUVN-DT (Digital) Channel: 46 (18.1) Network: Univision (SI),
and
WSAH-DT (Digital) Channel: 42 (43.1) Network: Independent

One deficiency in my current configuration is the RG-59/U coaxial cable connecting the antenna to the TV, which was installed by the previous owner of the house. I bought a spool of RG6 Quad Shield Solid Copper Core. I was planning to install the new cable when installing a new antenna.

Suspected obstacles to reception in general are the radio towers at the summit of West Peak in Meriden, CT. The FM and cell antenna cluster is only 4 miles away. I read on the forums that FM towers can be a problem but I don't know how significantly they affect my reception.

Here's my FM Fool Report



Currently, FM broadcast stations WHCN, WKSS, WPKT, WWYZ, and WZMX, also transmit from West Peak, as do NOAA with a weather broadcast station (WXJ42) on 162.4 MHz, and Amateur Radio station W1ECH with repeaters operating on 2 meters and 440 MHz. (as of February 2, 2009)

Thank you for your help arxaw and anyone else that may join in.

.
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Old 04-02-2012, 10:46 AM
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Originally Posted by 300ohm View Post

Well, you only have 2 vhf-hi channels in range. One is 56.1 NM which you could get on a reflectorless SBGH without NARODs. The other is a duplicate NBC channel you may not want anyway. If you do want that NBC, then I would build a reflectorless DBGH with NARODs, otherwise a simple reflectorless SBGH should do you well down to 22.8 NM.

TV Fool Report

Hi 300ohm

What length should I cut the NARODs to and how many do you think I need?

I'd like to try and discover the attic's maximum reception which hopefully yields a full selection of channels. Yes I understand vertical is much better. If the attic disappoints I will go to the roof.
So, I'm limited to a horizontal DBGH by the height of the attic. What design and parts do you favor for optimum horizontal combination? Is there an optimized DBGH model with phase lines for horizontal combination?

I am completely enthusiastic about building a DBGH.
Thank you for your help
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Old 04-02-2012, 07:41 PM
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What length should I cut the NARODs to and how many do you think I need?

For RF 10 thru 13, use 28 inch NARODs, measured 1/2" center of wire to center of wire (about 1/4" airspace) above and below the stubs of a SBGH.
Quote:


Is there an optimized DBGH model with phase lines for horizontal combination?

No, not yet. Horizontal phasing lines are very tricky to do. Also horizontal stacking gives a bit less gain than vertical stacking. You could use a coupler to combine the antennas in a horizontal stack, but only expect about a 1 to 1.5 db increase in net gain over a single bay after the balun and coupler losses.

I don't think you have much of a chance at RF 11 with any antenna in the attic, so youre really better off just building a SBGH.

Quote:


I read on the forums that FM towers can be a problem but I don't know how significantly they affect my reception.

With the exception of RF 11, which has lots of other things going against it also, those FM towers shouldn't significantly affect your reception.
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Old 04-02-2012, 08:02 PM
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Quote:
Originally Posted by Calaveras View Post

I poked around a little to see what I could dig up on the TiVo OTA tuner. There's the usual confusion between signal quality and signal strength but my take is that the TiVo (HD and Premiere) don't handle multipath very well. One discussion is here:

http://www.tivocommunity.com/tivo-vb...d.php?t=446075

One person notes that the TiVo uses the Microtune MT2131 chip set. That's interesting because my DTVPal DVR uses the same chip set and its multipath handling is identical to my Sony TV and the MyGoTV portable I have. I have major multipath issues here and any tuner less than the best is unusable. My Dish Network VIP-622 has a tuner with poor multipath handling and I can't use it.

The description of the SNR continually jumping around sounds like the equalizer is hunting around for the best setting and never settles on one. You wouldn't want it doing that because you'd lose the picture every time it tried a new setting. Sometimes when my Sony tunes to a channel it'll produce a picture and then retune and put the picture back up. If I watch the diagnostic screen when that happens I see a different SNR displayed on the 2nd tuning, usually better.

I can only speculate, but perhaps the firmware in the TiVo is having a problem in some situations settling on an equalizer setting. Other devices are using the same chips without this problem.

I hope my DTVPal DVR never breaks because it sounds like the TiVo would not work for me.

Chuck

My Dishnet DTV Pal PLUS indeed uses the MT2131 Double-Conversion
Tuner Chip (without any bandpass filter on input), as I verified by popping
off the shield cover and taking a photo.

Other users posted photos of the Dishnet DTV Pal (NOT Plus), which used
the Thomson DTT76809, a conventional Singe-Conversion "tin-can" tuner
with input bandpass filter to reject strong signals away from the desired freq.

So if you don't have the "PLUS" model, you don't have MT2131....

More info re tuners & chips inside CECB Boxes is found in "CECB FEATURES" below.
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Old 04-05-2012, 06:38 PM
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Building a house in a rural area and looking to mount an antenna either in the attic or on the roof. Planning to have two tvs hooked up initially and possibly a third down the road. I don't have much experience with antennas, amps, and other equipment that might be needed. What are your recommendations? Any advice would be greatly appreciated.

Attached is my TV Fool Report.

Thanks in advance!
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Old 04-06-2012, 03:37 AM
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Old 04-06-2012, 04:38 AM
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Old 04-06-2012, 06:05 AM
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I don't have much experience with antennas, amps, and other equipment that might be needed. What are your recommendations? Any advice would be greatly appreciated.

I take it that youll want the channels down to ABC, RF 13, NM 12.5 ? For that ABC station, youll need a preamp and and strong uhf/vhf-hi outdoor antenna in order to split the signal to 3 sets. The problem is, the strong channels above 50 NM in that general direction may overload. Youll have to aim for 16 degrees.

If you just wanted the stations in the green above 40 NM, you could probably get by with just a medium gain uhf/vhf-hi antenna in the attic.
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