OVER-THE-AIR DIGITAL TELEVISION RECEPTION FAQ: New to OTA? Start here! - Page 3 - AVS Forum
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post #61 of 248 Old 12-01-2007, 08:59 PM
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Quote:
Originally Posted by daMaster View Post

It's actually pretty simple to get your latitude and longitude from Google Maps. Enter your address, then when it shows up on the map click on "Link to this page". Copy & paste the URL into Notepad (or your favorite editor), and look for parameter &ll=xx.xxxxx,yy.yyyyy embedded within the URL. The x's are your latitude and the y's are your longitude (either one could be positive or negative depending on your location).

Now, can someone explain me my results from 2150.com please: http://www.2150.com/broadcast/defaul...=Show+Stations

Does the above report indicate that I can receive all of those channels? How do I figure out from that report which channels I can catch and where I need to direct my antenna to catch them?

www.2150.com/broadcast does not PREDICT which channels you can receive.

Unfortunately, www.antennaweb.org predictions do not work outside U.S.A.

However, you can use www.tvfool.com to PREDICT reception.
Attachment below shows both NTSC analog and ATSC digital channels.

Nearest stations are about 10 miles away, so try without an amplified antenna.
You may or may NOT improve distant performance with a Preamp---you could try
a low-gain, high overload type such as the W-G HDP-269.

You'll probably get most if not all of the "LOS" (line-of-sight) stations, but can
expect difficulty with "1Edge" and "2Edge" stations due to intervening terrain.
Be sure to visit TVFool web site for information on how to interpret these charts.
LL
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post #62 of 248 Old 12-01-2007, 09:21 PM
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Quote:
Originally Posted by Falcon_77 View Post

Yes, I would suggest giving S-video a try. It should be better than the RF out, depending on the quality of the RF modulator in the D* box. Then you can hook up the antenna to the RF in and have both D* and OTA with a change of inputs on the TV remote.

Most definately. Plus, I seriously doubt that D* even bothered to use a MTS (stereo) modulator for the audio. Even if they did, that is inferior to the direct baseband audio that is available on the audio out jacks.

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post #63 of 248 Old 12-02-2007, 08:34 AM
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Quote:
www.2150.com/broadcast does not PREDICT which channels you can receive.
Unfortunately, www.antennaweb.org predictions do not work outside U.S.A.

2150 isn't suppose to "predict" anything. No one can do that. As far as antenna web, their "predictions" don't amount to much inside the US.

Abundant OTA television is what makes this country different from all others. Lets keep it this way.
The Internet is no place for streaming video.
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post #64 of 248 Old 12-03-2007, 12:31 PM
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There may not be an answer to this one:

I live about 60 miles east of LA - without cable or satellite - and use an RS 15-2187 HD antenna to grab the OTA signals. All the networks' digital broadcasts are currently on the UHF band and we get crystal clear reception (except for Channel 13). Is there any way to tell what is going to happen to my reception in 2009 once analog goes away and some (all?) of the digital signals revert from UHF back to VHF?
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post #65 of 248 Old 12-03-2007, 05:54 PM
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Quote:
Originally Posted by Landlubber View Post

There may not be an answer to this one:

I live about 60 miles east of LA - without cable or satellite - and use an RS 15-2187 HD antenna to grab the OTA signals. All the networks' digital broadcasts are currently on the UHF band and we get crystal clear reception (except for Channel 13). Is there any way to tell what is going to happen to my reception in 2009 once analog goes away and some (all?) of the digital signals revert from UHF back to VHF?

Since the new DTV coverage is "supposed" to replicate the number of existing analog users,
a good guess is to simply see if you can receive the analog channels.
Of course, you may find you need a "real" hi-VHF antenna.

Since many Sat Receivers don't DO analog, try it with the analog tuner in either a TV, HDTV or VCR.
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post #66 of 248 Old 12-04-2007, 11:05 AM
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Well, for the record - and not surprisingly - for Channels 2 (CBS), 4 (NBC) and 5 (CW) my analog reception is relatively poor; and for Channels 7 (ABC), 9 (Ind), 11 (Fox) and 13 (MN) the reception is actually pretty decent. (And it is still not clear to me why we get the analog signal for 13 and not the digital.)

I guess that means that if the networks follow the FCC (strong?) suggestion of staying away from 2 thru 6, I shouldn't have issues...
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post #67 of 248 Old 12-04-2007, 11:22 AM
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Quote:
Originally Posted by Landlubber View Post

And it is still not clear to me why we get the analog signal for 13 and not the digital.

Might it be because the digital channel isn't on VHF-13, but on a UHF channel?

Quote:


I guess that means that if the networks follow the FCC (strong?) suggestion of staying away from 2 thru 6, I shouldn't have issues...

In a majority of the cases, the networks have nothing to do with a station's request to go back to the analog channel for digital, even if the station is a network O&O. Local engineering might have a pretty big say as to determining if the station reverts or not. A station that is an affiliate of a network will determine on their own, and/or in consultation with the parent company, what they requested (revert or not).

In some cases, the station wasn't allowed to revert, which happened in my area.

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post #68 of 248 Old 12-04-2007, 02:37 PM
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Quote:
Originally Posted by videobruce View Post

That reasoning (if you call it that), has always escaped me. Seems to indicate some type of 'snob' level. Why 'loop' an OTA antenna through a satellite box? Connect it directly to the TVs' RF input. Needed "that"?? What an antenna? Nothing has changed in 10 years. Huh???? What/where did you ever get that idea from????? The "HD" part is only marketing hype. Remember the "Color Approved" antennas from the 60s'??

Truly I don't know the reasoning behind not wanting an antenna on the roof - they already have a Directv dish on the roof!

"Looping" through the box was really just an oversight on my part. I was rushing to try to get everything hooked up. I'm not as knowledgable about HDTV and digital signals as I'd like to be. This is my first experience with HD and digital signals (always had D* or E*).

Another consideration was trying to avoid having to retrain the user on how to view their programming. It was bad enough having to hook up the D* box and DVD to 2 different inputs (tuner & component) and trying to teach them which input to select. Moving D* to composite and OTA to tuner might have pushed them over the edge. I have since given him a switch to split the D* and OTA signal into the tuner input. I'm waiting to hear back if it was successful.

"That" was referring to the "old days" of needing a waiver to receive network channels via satellite (back in the Primestar days). Living in a flight zone they've always had difficulties receiving OTA signals. They've had satellite (starting with Prime*) since I've known them, so I don't know what they did before that.

I'm trying to convince them to just upgrade their D* service to HD, but they don't want to lose pricing and special programming left over from Prime*. Last time they tried to add a $5.99 channel they were told their programming had to change - they would lose east/west coast network channels and add a total of $16-17 to the monthly bill.


As I'm sure you are aware, not everybody happily accepts these new changes. Some people need to be dragged, kicking and screaming!
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post #69 of 248 Old 12-04-2007, 02:56 PM
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Quote:
Originally Posted by Landlubber View Post

Well, for the record - and not surprisingly - for Channels 2 (CBS), 4 (NBC) and 5 (CW) my analog reception is relatively poor; and for Channels 7 (ABC), 9 (Ind), 11 (Fox) and 13 (MN) the reception is actually pretty decent. (And it is still not clear to me why we get the analog signal for 13 and not the digital.)

I guess that means that if the networks follow the FCC (strong?) suggestion of staying away from 2 thru 6, I shouldn't have issues...

The upper channels have higher cable/RF Splitter losses and perhaps also lower antenna gain.....

I punched 92350 zipcode into www.tvfool.com and see that digital KCOP-DT (13.1 MyN on ch66)
is two channels above nearby KSGA (ch64, 2-3 miles away).
This strong station is probably preventing reception of the weaker KCOP-DT.
KTTV-DT (11.1 FOX on ch65) is on an adjacent channel, but is about 6 dB stronger.

TVFool presumes omni receive antennas and calculates that KSGA is about 20 dB stronger than KCOP-DT.
Because it probably isn't in a sidelobe null (typ. +/- 30 degrees from max), the antenna can
only provide moderate gain suppression towards KSGA.

ATSC A/74 Performance Guidelines (based on various tests) indicate that
a digital station can be WEAKER than an adjacent analog station by about 35 dB (+/- 5 dB) and
next adjacent (N +/- 2) channels by about 40 dB (+/- 10 dB, depending on desired signal levels).
However recent FCC OET 07-TR-1003 tests revealed that tested HDTV's were actually slightly MORE
sensitive to interference from next adjacent (N +/- 2) channels as from adjacent (N +/- 1) channels.
Hence 13.1 may be MORE sensitive to interference than 11.1.

Never the less, stronger KSGA "shouldn't" prevent reception of KCOP-DT due strictly to adjacent
channel considerations. However, AGC "capture" by the stronger station as well as non-linear
intermodulation distortion products may still be a problem.


You may be able to add additional suppression towards KSGA by installing a chicken-wire "fence" in your attic.
Keep it as far away from the antenna as possible to minimize perturbing the antenna pattern.....
Since you can receive KTTV-DT, maybe you only need a little more suppression.

BTW: You really need to also tweak the antenna back and forth to see if you can
"steer" a null towards KSGA....

============================
05Dec07: CORRECTIONS are in BOLD
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post #70 of 248 Old 12-05-2007, 03:00 AM
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Note: if following is getting a little too "in depth" for this thread, Doc/mods by all means feel free to edit or remove the following post :

Quote:
Originally Posted by holl_ands View Post

TVFool presumes omni antennas and calculates that KSGA is about 20 dB stronger than KCOP-DT.

Don’t mean to split too fine of a hair here, as that explanation “works” ...

However, think it is important to note TVfool predictions do not actually presume anything about performance of receive antenna. They are predictions for the signal level as it exists in "free space” at a optional user specified height, which of course is also “omnidirectional” in nature, so to speak …

But, the transmit antenna performance/directional pattern(if any) is taken into account by tvfool predictions. The ERP value given in the plots is directly related to this.

Quote:


ATSC A/74 Performance Guidelines (based on various tests) indicate that an adjacent analog station should be WEAKER than a digital station by about 35 dB (+/- 5 dB) and next adjacent (N +/- 2) channels by about 40 dB (+/- 10 dB, depending on desired signal levels).

The –35db in for N +/1 (given -53dbm signal level for desired signal) refers to the “Desired” signal for the desired to undesired(D/U) ratio expressed in A/74 document, as well as elsewhere as described in more detail below ...

While you’d think given the way they express it as “NTSC interference into DTV” they “mean” the opposite .....

Actually, in the ATSC A/74 document, table 4.2 indicates a receiver meets A/74 guidelines if it can successfully decode a desired DTV signal w/o impairments if the desired DTV signal is -35db weaker than the undesired 1st adjacent channel analog station given the desired signal level is at -53dbm. -40db weaker desired DTV signal than a NTSC analog at N +/- 2 with desired signal level at -53dbm.

I think The D/U ratios as expressed in :

#1). ATSC A/74 document

#2). FCC’s OET bullitin #69, and rules such as are specified regarding applications/changing DTV allotments for various channel relationships here in CFR 47, Sec 73.623 ,

#3) in the FCC OET 07-TR-1003 report entitled “Interference Rejection Thresholds of Consumer Digital Television Receivers Available in 2005 and 2006” :

Is well described in the “Executive Summary”/Interference Rejection section on page ix of OET-07-TR-1003 report, somewhat near beginning of the document as quoted below (I’ve bolded the portion of this of most interest, but thought it necessary to include the rest of these 2 paragraphs in the quote ) :

Quote:
Originally Posted by FCC OET report OET 07-TR-103 page ix View Post

INTERFERENCE REJECTION TESTS

The out-of-channel interference rejection threshold of consumer digital television (DTV) receivers was measured by supplying an ATSC 8-VSB* signal (the desired signal), along with one or two undesired signals, to the antenna terminal of a DTV receiver and then adjusting the level of the undesired signal(s)to the point at which picture degradation begins to be observed—a point known as the threshold of visibility (TOV) of degradation. In such testing, the DTV receiver is tuned to the channel number of the desired signal. The undesired signal (the potential interferer) is placed on another channel, either above or below the desired channel.

We refer to the desired signal power at the input to the DTV receiver as D and the undesired power when adjusted to the threshold (TOV) as U. It is traditional to express interference rejection performance in terms of the ratio D/U. When D/U is expressed in decibels (dB), it is typically a negative number for out of-channel interference; that is, the undesired signal level is greater than the desired signal at TOV. Low values (i.e., large negative numbers) represent good rejection performance; high values (small negative numbers) represent high susceptibility to interference. D/U ratios measured for this report ranged from below -74 dB to -20 dB. Results in this report are presented both as D/U ratios and as threshold values of the undesired signal power U in order to meet the needs or preferences of different analysts.

And, this short quote from the same report should also further clarify this :

Quote:
Originally Posted by FCC OET report OET 07-TR1003 Chapter 4 page 4-3” View Post

“Consider the case of a D/U ratio of -60 dB—meaning that the desired TV signal power is 60 dB below the
power of the interferer .... "

Otherwise, it would make no sense whatsoever that FCC has allocated in some cases some 1st adjacent channel DTV+NTSC channel allocations in the same market, even squriting RF off the same stick(tower) for that matter, as is case the for stations such as WCPO 9 analog/WCPO-DT 10 Cincinnati, in my area ..... check tvfool signal predictions for those two stations for 45042 .... For my location, it predicts -74.3dbm for WCPO-DT 10, -60.1dbm for WCPO 9 analog ... Since these broadcast from the same tower(316Kw ERP analog “peak” power on 9, 16.3KW ERP “average” DTV power, both with non-directional antenna patterns) obviously they are in same direction .... Obviously, the signals are generally of the same or similar *relative* strength(between each other) for everyone in their service area, and yes, it seems it works just fine with all my receivers with the DTV signal, say, around -14db or so below the NTSC N-1 signal ….. (Hopefully that's the case for everyone in the area, but I can't say) ...


Quote:


However recent FCC OET 07-TR-1003 tests revealed that tested HDTV's were actually slightly MORE sensitive to interference from next adjacent (N +/- 2) channels as from adjacent (N +/- 1) channels. Hence 13.1 may be MORE sensitive to interference than 11.1.

Indeed, a summary in chapter 5 of those results indicate it is true at low tested signal levels(+3db above threshold for desired signal) suspectibility to interference from N +/-2 signals being worse than N +1/-1 is pretty much the cases for all the receivers(which was unexpected, it seems) they tested. But, the report also summerizes that only 2 of the 8 receivers tested “worse” on N +/-2 than N +/- 1, and one more worse on N+2 only at somewhat higher signal levels (for desired signal) …

If you look at table A-5 (appendix A), for the resuts with Desired signal at -53dbm, the median D/U among all the receivers actually beat the ATSC performance guidline by 1.5 db, and the best performance was –49db D/U, 9db “better” than ATSC A/74 … OTOH, the worst receiver is shown with –27.4 db D/U, 13db WORSE than A74 guideline, and a whopping 22.5db difference in performance between the best and worst receiver !

The summary of “Rejection performance” on page x is also interesting, it notes that no receiver tested fully achieved ATSC A/74(which is “less stringent than the receiver performance assumptions on which current DTV interference protection criteria are based” (I.e. OET bulleitin #69 ) ... With the best-performing receiver tested failing only on one channel offset, and there by only 1db … I’d certianly like to know which receiver that is, especially given the poor performance on some channel offsets by some of the worst performing receivers tested ? (as much as 24 db “worse” than A74 !!) …. For that matter, I'd like to know the makes/models/etc of all those receivers tested

Jeff
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post #71 of 248 Old 12-05-2007, 07:58 AM
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While I appreciate your efforts, Jeff, most of it is in fact lost on me. I knew it was going to be a challenge when I came to a site called "AV Science Forum".

That said, I understand what holl_ands means when he says that tvfool "assumes" an omnidirectional antenna. To me, that has nothing to do with performance (how well it receives), only that tvfool will tell you what signals the location in question is capable of receiving, regardless of direction.

I also understand that there is a nearby signal on Channel 64 (4.2 miles away, at 250 degrees from true north) that may be interfering with a weaker, more distant signal on Channel 66 (50 miles away, 285 degrees from true north). So if I rotate my antenna a few degrees to the north, I might be able to reduce the interference from the signal from KSGA (Channel 64) that may be keeping us from receiving KCOP (Channel 13.1/66).

I am still not clear on how to apply the chickenwire screen solution. Do I surround the antenna (with as large a radius as possible)? Or do I only erect it as a "shield", leaving an opening on the northwest quadrant to accommodate the signals from Mt. Wilson? Or is there a third option? For the record, my antenna is facing WNW, approximately 12 feet from the west, gable end of our house.

Again, as a layman I appreciate the many good things on this site. And at least this thread doesn't get as nasty as some of the discussions comparing LCD to plasma.
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post #72 of 248 Old 12-05-2007, 12:48 PM
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Quote:
Originally Posted by Landlubber View Post

That said, I understand what holl_ands means when he says that tvfool "assumes" an omnidirectional antenna. To me, that has nothing to do with performance (how well it receives)

In terms of directivity(and a true Omnidirectional antenna which has none), certianly.

An Omnidirectional(or any) receive antenna has performance characteristics(such as gain) which are not modelled by TV fool, most signal "predictions"(such as what FCC does) are based on certian performance charactieristics of receive antennas used, that's all I was saying.

I only brought it up because it was not "exactly" clear to me whether or not he was refering to transmit antenna(which *is* modeled whether it's omnidirectional or directional) or receive antenna, I assumed he meant receive antenna but wasn't sure ....

Quote:


.... only that tvfool will tell you what signals the location in question is capable of receiving, regardless of direction.

Yes, certianly ....

Quote:
Originally Posted by Landlubber View Post

I also understand that there is a nearby signal on Channel 64 (4.2 miles away, at 250 degrees from true north) that may be interfering with a weaker, more distant signal on Channel 66 (50 miles away, 285 degrees from true north). So if I rotate my antenna a few degrees to the north, I might be able to reduce the interference from the signal from KSGA (Channel 64) that may be keeping us from receiving KCOP (Channel 13.1/66).

I wonder what a polar plot for the RS 15-2187 Looks like? Specs on it on radio shack website indicate that whatever sort of antenna it actually is, it is apparently inside a radome ... and the RS specs show 1/2 power beamwidth on UHF is 60 degrees, which means it's directivity is not very good, and a station 30 degrees(1/2 of the 1/2 power beamwidth, which would extend 30 degrees on each "side" of where antenna is aimed) from direction antenna is aimed should only be rejected by about 3db (1/2 power) ... so with antenna aimed around 60degrees or a little more "away" from KSGP, it's possible you may perhaps(just a wild guess really) be getting around say, 10db or so rejection of KSGP-LP signal with your antenna aimed as it is, although that should really be enough(actually, No rejection of it should really be enough), I'd think.

Another "interesting" spec on 15-2187 on RS website shows average Front back ratio of 17db on UHF .... If anywhere near being true, that's actually pretty good, as usually with directional antennas(such as yagis), you have bigger nulls "off the side" of antenna than off the back ....

Keep in mind, KSGP-LP is a analog, Low power station. If the predictions from TVfool were absolutely "correct", based on FCC tests of various, recent DTV receivers this really shouldn't be a interference issue(even with use of a omnidirectional receive antenna) , as the predicted signal difference of 20db more undesired signal from KSGP-LP 64 than the desired KCOP-DT 66 signal is less difference than the worst performing receiver FCC tested these channel relationships for, and signifcantly less than the best performing receiver, for which the KSGP signal could be approximetely 29db stronger and reception of KCOP-DT could still be acheived ....

HOWEVER, the tvfool dbm values are predictions which are based on F(99,99) curves, and it very well may be the case that the signals you're actually getting may be significantly stronger than the predictions in dBm show, which will of course be even stronger with the gain added by your antenna/amp.

Of the receivers FCC tested for interference rejection given a desired signal level of -68dbm(the closest "in the ballpark" figure to your TVfool predicted KCOP-DT 66 signal of -63dbm via a "zip code" plot), The *worst* receiver tested was able to achieve DTV reception with a 2nd adjacent(N +2 signal) 28db stronger -- that should hopefully be pretty much be a "worse case" scenerio, and the best performing receiver on this test could withstand a N+2 signal 50db stronger than the desired signal+still acheive reception, the median of all receivers tested was a -41db D/U ratio ....

While KTTV-DT 65 (-57.2dbm) is predicted to be 6db stronger by TVfool(and these are only predictions, keep in mind), at signal levels for the desired signal of -53dbm, Most receivers tested by FCC, as one would expect performed worse in interference rejection tests with a 1st adjacent channel interfereing signal. The best performing receiver tested acheived reception of the desired signal with the desired signal as much as 40db weaker than the lower first adjacent channel(N-1) - 9db "worse" than the best receiver for the 2nd adjacent channel (N-2) tests -- and the median of all receivers was a -41.5db D/U ratio (almost exactly the same as N -2 test) ... But, the worst receivers did perform significantly better(by about 7db than N-2 tests) ..

Now, if the signal levels are actually signficantly higher than Tvfool predictions(lets say about 20db higher at receiver input), as you might predict, the receivers selectivity becomes worse per the FCC tests. With the desireed signal at -28dBm for instance, the receivers tested all had D/U's of about -26db for lower 2nd adjacent channel interference, and D/U's of about -21db for lower 1st adjacent channel interference ... Meaning the interfering signal caused DTV reception of desired signal to drop below threshold at these higher signal levels if the desired signal was at or more than 21db weaker than a 1st lower adjacent channel signal, or 26db(or more) weaker than a 2nd lower adjacent channel signal. *IF* however this was the case, then I would expect your KTTV-DT 65 signal to be non-receivable or have reception related "glitches" as well as KCOP-DT 66 ....

And, generally speaking, even though it is predicted as 6db stronger than KCOP-DT, Assuming you are getting good reception of KTTV-DT(digital) on 65, I'm skeptical concerning interference from KSGP-LP being the issue of concern, here(even if you were using a omnidirectional antenna, although that might cut things pretty close depending upon what the deired signal level actually is), and you certianly shouldn't need 55db less signal from KSGP-LP than KCOP-DT.

If there is a "interference" type issue involved, (rather than something else such as multipath or weak signals if the amp isn't working/isn't being powered properly/etc - note - in most cases, if a amplifier is unpowered, the unpowered circuitry in the amp will attenuate signals *greatly*, much much more than if the antenna wasn't amplified) ..... If anything, I'd suspect it may be more likely to involve the tuner/amp being overloaded(because your using an amp where there are some fairly strong signals around) .... I don't know anything about the real "specs" of the amp in that RS antenna, just based on what I do know (10db gain) if your going to use an amp, that would be the sort of "specs" you'd probably want in your sitatuation.(although, actually, you really shouldn't need a amp at all given the predicted signal levels involved, unless you need it for distrubution to various devices) ... But generally speaking, High power station KVCR(analog+digital) would probably be the biggest concern (unless perhaps there may be very nearby FM stations or other sources of RF not on TV band frequencies which could still overload things and cause IMD (intermodulation distortion) .....

Quote:


I am still not clear on how to apply the chickenwire screen solution. Do I surround the antenna (with as large a radius as possible)? Or do I only erect it as a "shield", leaving an opening on the northwest quadrant to accommodate the signals from Mt. Wilson? For the record, my antenna is facing WNW, approximately 12 feet from the west, gable end of our house .....

My guess is going that route may involve quite a bit of experiementation(which may or may not yield any positive results) ... But basically, If you want to increase rejection of KSGP-lP, seems to me you would want to put the screen generally Southwest of the antenna, and you wouldn't want it between the antenna+Mt Wilson .... - As holl_ands said, perhaps in the attic would work ....

Quote:


Or is there a third option?

If I were you, FWIW, I might consider trying an unamplfied antenna that offers better performance(especially better directivity) than the antenna you are using, then adding an amp later if necessary or desired ....

Although, OTOH, of course, as you've already noted, KCOP-DT will be moving to ch 13 in 14 months, so you might not want to put too much "effort" into it(and if you do you don't want to "concentrate" only on UHF, as you'll want to make sure your Hi-VHF reception remains good), as chances are very good that if you receive good analog reception on Hi-VHF(ch 7-13) as you've reported, the same will be true for the digitals, including KCOP-DT 13 ....

Quote:


Again, as a layman I appreciate the many good things on this site.

I do hope I've explained the above "clearly enough" for it to be at least somewhat understandable(I'm doing my best, which is all I can do !), there are many factors which can effect OTA reception, and it can be very "complicated" to post about it and try to "guess" what may be causing any given reception problem in any given case, and even more complicated(and difficult) to post about it in "plain english" without writing a "book" so to speak ! .....

Jeff
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post #73 of 248 Old 12-05-2007, 03:12 PM
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Jeff:

I can say that I am comprehending at least 75% of what you're saying and, for what I need to know, that is more than enough. I did not spend a tremendous amount of money on this antenna, but it does suit my needs. What you say regarding its "directivity" makes sense, and what you suggest about the chicken wire confirms my thinking on that as well.

Appreciate your help and your thoughts.

Glenn.
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post #74 of 248 Old 12-05-2007, 03:33 PM
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Oh bother!!! I've stumbled into the negative D/U rabbit hole....knowing full well...after all it was right in plain sight!!!!

I corrected the post above (in BOLD).
Adjacent and Next Adjacent Channels "shouldn't" be causing problems.
But further analysis would be needed to address non-linear intermod effects and related AGC Capture effects
(strong signal can desensitize and reduce dynamic range for desired signal, esp with multipath).

=================================
Firstly, get the antenna up off the (signal sucking) attic floor and give it half a chance of working by aiming it.

For the 92350 Post Office location, Mt Wilson is towards 285 degrees True North (272 Magnetic)
and KSGA is towards 224 degrees True North (211 Magnetic).
Hence Mt Wilson is 75 degrees to "left" of True North and KSGA is 61 degrees further "left" from Mt Wilson.
[You should punch your address into www.tvfool.com to refine these numbers....]

An antenna with a "nominal" 60 degree beamwidth only approaches that for lowest channels.
For upper channels they (and probably also the R-S) would have much narrower beamwidth.

Suppose we assume the R-S is "similar" to the CM-4221 wrt beamwidth:
http://www.hdtvprimer.com/ANTENNAS/cm4221.html
It may approach 60 degree beamwidth for CH20, but is closer to 40 degree beamwidth for CH60.
And is about 20 dB down at +/- 60 degrees and hence should significantly suppress KSGA.

================================
To mount the antenna in the attic, a simple metal or plastic pipe (Sked 40, either 1-in or 3/4-in) can be
attached from an overhead rafter (see post #64 above and below attachment), so the antenna
can be twisted back and forth to aim it.

Once you've figured out which way is "North", eye-ball where you think Mt Wilson is and then OFFSET the
antenna from about -45 degrees to +45 degrees in perhaps 15 degree increments, having someone write
down how well each position works for 2.1, 11.1 and 66.1 (13.1)...a signal percentage display helps.
[Before your HDTV acquires "synthetic" 13.1, you'll need to punch in the REAL channel on 66.1]
LL
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post #75 of 248 Old 12-05-2007, 03:56 PM
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holl_ands:

The mounting hardware for my antenna is sitting safely in my garage. I understand that I took a very lazy route and basically just "threw" the antenna up in my attic space. It IS pointed in the general direction of Mt. Wilson, but I will elevate it and rotate it from side to side to see what happens. Ultimately, I know that my reception will be no worse than it is now.

Thanks.

Glenn.
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post #76 of 248 Old 12-05-2007, 04:45 PM
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KCOP-DT (13.1) was the only station I couldn't get at my son's location (attic, East of Murrieta, 75 miles from Mt Wilson).
But since there was/is nothing worth watching in HD on MyNetwork, I haven't had any reason to try anything different....

If you check the L.A. Thread, you'll see that numerous people have problems with KCOP-DT...and don't really care....
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post #77 of 248 Old 12-05-2007, 10:20 PM
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My wife and I talked about it and we couldn't think of a single thing we watch on KCOP, either.

By the way, my antenna is now mounted on a platform in the attic space, using the arm and bracket that came with it. I have not done any further adjusting, but if KCOP is all we're missing, we aren't missing much.
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post #78 of 248 Old 12-05-2007, 10:32 PM
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OT, but An HD airing of "Cider House Rules" and a HD Bikini show (both were aired last season) are the only things I've watched on MyTV, LOL ...

Jeff
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post #79 of 248 Old 12-06-2007, 08:27 AM
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Nightwatchman;

Thanks Jeff, for the D/U explanation in message 75. Somehow, in the trades they seem talk all *around* the topic without clearly stating what you did that one message.
tnx agn
Kelly
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I have an Olevia 232V 32" HDTV (built in tuners for OTA) and am trying to get OTA digital broadcasts. I am in NNJ. This is actually my son's, but I am borrowing it from him. I last used it at the end of the summer it could pick up fox (5.1), and channels 41 and 50/51. Now it can only get 41, 51 and 68 after a scan. Scans were done on both air and cable settings.

Trying to better understand the real issue here I have been doing some research. I have used antennaweb.org to determine potential stations. I gather from some of the posts on this site that there are those who do not feel this is a reliable resource; however, I believe it is good enough for my purposes as I am close to the source, no real interference issues, and get excellent OTA analog signals.

Most of the channels, according to antennaweb.org, are coming from the same direction (160 degrees, which if I understand this correctly is 20 degrees east of south). This seems to explain 41 and 68, but 51 comes from 212 degrees. Thus it appears the antenna has a significantly wide range.

All the major stations and independents (2, 4, 5, 7, 9, 11, 13) are listed at the same distance and direction, so I assume their antennas are located together, but I can't get a one of them in. They are in the same direction and distance as the ones I can get. I tried manual entering in the actual frequency into the TV, but it can't find the signal. I find it incredibly difficult to believe that the majors have a weaker signal then these lesser stations.

I am at a loss to make sense of this, perhaps someone can comment on this.
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post #81 of 248 Old 02-06-2008, 11:51 AM
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How far away are you from the stations that you're trying to receive? What type or model of antenna are you using? Indoor or outdoor? It would help if you posted your antennaweb.org results, or better, from tvfool.com (which provides more technical information). Also, use your actual address or coordinates instead of just your ZIP code for input, if you haven't done so already. Parts of northern NJ are rather hilly or even mountainous, which can definitely affect reception.
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According to AntennaWeb I am within 20 miles of most of the stations. I am using a roof mounted antenna and do not know the manufacturer. I am located near Paterson before the hills and have a pretty straight line of site to NYC. I can get excellent analog reception and thus have never felt the need to get cable.

I used the street address and checked the street level map for correct location. How would I post my AntennaWeb results?
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post #83 of 248 Old 02-06-2008, 03:27 PM
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I ran the search at TV Fool. It gives similar info as AntennaWeb. It seems to show that I shouldn't have any problem getting a digital signal.
LL
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post #84 of 248 Old 02-18-2008, 09:23 AM
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Hi all. I built an HTPC a week ago and this weekend put a Channel Master Advantage 3020 directional antenna into my attic with the smallest CM preamp attached (I couldn't find a Spartan 3 preamp that wasn't missing parts).

A large, directional antenna with preamp was recommended to me by antennaweb.org. My zip is 75028. Nearly all stations (and all that I care about) are at 163-164 degrees at a distance of 32 to 35 miles. I could have gone with the next-smaller antenna, but went with this one "to be sure".

Before this, with a small, unamplified antenna attached to my DirecTV dish I was getting:

1. ABC affiliate at channel 9 (only VHF digital station) showed very spotty performance. Weak signal strength (35%) and frequent loss of picture ("stuttering").
2. No reception of local independent station at channel 18. Low power transmitter that I wasn't able to get even with my TV's built in tuner.
3. Good performance on most other stations, although all showed signal strength of no more than 40-45%. Local FOX affiliate at channel 35 would cut out every now and then.

After the antenna and preamp installation I am seeing a bit of a slip in performance:

1. All channels now show signal strength of above 50% with some up to 75-80%.
2. ABC affiliate comes through solidly with no stutter.
3. I can now receive IND station at channel 18 with no apparent problems.
4. FOX affiliate, however, now shows more stuttering than before. Signal quality seems to be down vs. what I was seeing before.
5. My CW affiliate at channel 32, which I received fine before, is *extremely* unstable and can't lock onto a good signal at all.

My general question is: "What should I try next"? HMA rules don't allow me to put this monster antenna on the roof, and I currently have it in the only space where it reasonably fits in the attic. There is, I am sure, some interference from the roof/shingles/gutters that I am contending with.

Here is my short list of options:

A. Ensure antenna is pointing at 163 degrees. Currently pointing is estimated, so perhaps a more direct point would help.
B. Try the antenna without the preamp. Could I be overpowering the problem signals? This seems unlikely.
C. Get the better preamp. Could this help?
D. Perform some adjustment on the antenna. I am not sure other than pointing what I can do here. The setup does not appear to have anything on the UHF end that can be adjusted. Anyone else with this antenna may know more.
E. Given that my problems are with channels 35 and 32 it could be that the FOX affiliate is masking the CW one. Is this possible and how would I correct for it.

My experience with this sort of thing is fairly limited, so any help would be greatly appreciated.
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post #85 of 248 Old 02-18-2008, 09:43 AM
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My first suggestion would be to try reception w/o the pre-amp. In general, I would suggest that all installations be tried without a pre-amp at first. Too much signal can be just as bad as too little. Which pre-amp are you using? At ~31-34 miles from the towers, you should not need a high powered pre-amp.

Also, if your amp has a PIM (Power Insertion Module), please be sure to remove both the PIM and the pre-amp from the system. Unplugging the PIM will result in substantial signal degradation. Care must also be taken to make sure that the PIM is directly connected to the Pre-Amp, w/o any splits, etc., in between the two.

Attics have dead spots, which will affect different frequencies in different ways. The 3020 is a good antenna, but from first hand experience, I know how hard it is to move around. I could not connect the VHF and UHF portions in my attic and I eventually removed it. Also, the 3020 owes much of its size to Low-VHF reception, which is not needed in most areas for DTV. WFAA is on 9 for DTV, which only needs a smaller upper VHF antenna. In 2009, WFAA will move back to 8 and be joined by KFWD on 9 and KTVT on 11.
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Quote:
Originally Posted by BTDT View Post

HMA rules don't allow me to put this monster antenna on the roof,.

HMA rules be damned. If you own the house, or renting the house, you are allowed, by law, to put your antenna on the roof. All such HMA rules were struck down by law.

Just show them the following document:

http://www.fcc.gov/mb/facts/otard.html

If they threaten to sue, tell them to get their wallets out, because they will lose.

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post #87 of 248 Old 02-18-2008, 09:59 AM
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Quote:
Originally Posted by mrvideo View Post

Just show them the following document:

http://www.fcc.gov/mb/facts/otard.html

I would like some clarification on this:

Quote:


The rule applies to video antennas including direct-to-home satellite dishes that are less than one meter (39.37") in diameter (or of any size in Alaska), TV antennas, and wireless cable antennas.

Does the 40" measurement only limit satellite dishes? In other words, are Yagi type antennas with boom lengths over 40" protected as well?

I had previously read this as to preclude antennas over 40" in any dimension to not be subject to the rule, but perhaps that is not the intent. If anyone can clarify, it may change my thinking at some of my sites.

With the physical size requirements for VHF antennas, the 40" limit did not seem appropriate.
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post #88 of 248 Old 02-18-2008, 10:12 AM
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Quote:
Originally Posted by Falcon_77 View Post

Does the 40" measurement only limit satellite dishes? In other words, are Yagi type antennas with boom lengths over 40" protected as well?

The 40" rule is for satellite dishes. OTA antennas for broadcast TV reception can be whatever size it takes to get the signal. There is a height restriction though, which you will probably not hit.

Antennas for any other use, AFAIK, are not protected.

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post #89 of 248 Old 02-18-2008, 10:37 AM
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I am using the Channel Master 3039 preamp, the low end of their offerings, primarily because it was the only one I could in stock at 3 Frys stores. (I found a couple of marked-down, ripped-open, 3041DSBs but these were both missing the part that attaches to the antenna!)

I can confirm that the preamp is attached via a single, unsplit or spliced, coax cable.

I agree that the 3020 may have been a bit of an overkill, since I only had one VHF station to worry about (however, that was one of my biggest problems as well). I also agree that the 3020 is a *monster* to maneuver. I am actually quite proud of the positioning I have done so far, but it is completely inflexible to go anywhere else.

For grins I will try the setup without the preamp. The on-roof antenna was not preamped before so this one *should* be better even without it -- that is, unless the attic is causing more problems than I would hope.

I am really going to hate tearing this thing down and returning it if I have to, but I suspect I really didn't need this antenna. If it all works, however, then I won't touch it.

My wife never goes up in the attic. If she saw this thing I can just imagine what her reaction would be .
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post #90 of 248 Old 02-18-2008, 10:41 AM
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Quote:
Originally Posted by mrvideo View Post

HMA rules be damned. If you own the house, or renting the house, you are allowed, by law, to put your antenna on the roof. All such HMA rules were struck down by law.

Just show them the following document:

http://www.fcc.gov/mb/facts/otard.html

If they threaten to sue, tell them to get their wallets out, because they will lose.

Yes, but even I would have to question a 13-foot antenna mounted on the peak of my roof. I did a visual check of the neighborhood yesterday and didn't see a single house with an independent OTA antenna. There were many dishes, and some with small attached antennas. A nearby neighborhood had several OTA antennas, but they were at most half this size (hint?).

I am going to assume for now that the larger size may help offset my in-attic installation. We shall see.
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