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post #91 of 654 Old 05-29-2007, 04:22 PM
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Andy - Hope you had a nice vacation. The "post-holiday" comments. I'm back at work today, so I hope it doesn't sound too much like a design review...

MarkF70 - Welcome to AVS forum (1st post). I agree that the behavior has changed. In Firefox, right-click mouse --> View Background Image. Then, you should be good to go as an 800 x 600 .png image. You can also get it from the page info media properties. A "button" to save the image is needed.

Bug: The results table only show stations down to the "red", but the spectrum plot shows stations in the "gray". Please add the "gray" stations to the table output.

Graphics suggestion (mentioned before): Remove the multicolor background on the radar plot (outer ring).
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post #92 of 654 Old 05-30-2007, 01:08 AM - Thread Starter
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Quote:
Originally Posted by Nitewatchman View Post

I haven't investigated the details concerning what the differences regarding the F(99,99) propagation curves for the modelling are, and I gather from andy's comments that has something to do with this ... And, I may be missing something or not interpeting something "correctly" here, and perhaps it's better the way it is, or perhaps if andy does decide to shift the values shown by +10db as he indicated in one of the posts referrenced above would be more accurate, or perhaps a little more or less of a shift from the values it's currently showing would be more accurate ...

For the technically interested...

The two parameters for the Longley-Rice modeling represent the Confidence and Reliability measures of the prediction. These two parameters are designed to account for statistical variations in temporal (time), spatial (position), and ground constitution factors in signal propagation. The model is based on the laws of physics and the way that EM waves propagate through the air and over a terrain surface, so the propagation losses are actually a function of things that affect the refractive index of the air (type, density, humidity, ionization, etc.) and the things that affect the permissivity and permittivity of the terrain elements (water, sand, ferrous rock, tundra, rain forrest, etc.).

Since nobody has exact data about the composition of the Earth along every inch of terrain, and since the EM properties of the air and Earth change over various weather conditions and seasonal changes, the best that the model can do is approximate the expected losses with statistical bell curves that roughly describe the range of losses that can occur over particular types of terrain/climates.

When the engineers were designing and testing the model (it supposedly took over 270 engineers about 3 years to do this), they created statistical distribution curves for seven different types of terrain/climates, which were included in the original paper describing the model. These seven "radio climates" are namely: 1) equatorial, 2) continental subtropical, 3) maritime tropical, 4) desert, 5) continental temperate, 6) maritime temperate over land, and 7) maritime temperate over sea. For my modeling tools, I use the continental temperate tables since they are the best estimation for North American terrestrial television.

The Confidence and Reliability parameters for the model determine where on the bell curves you take your propagation estimates from. F(99,99) is almost a worst-case scenario, meaning that if the weather, terrain, and other factors are at the far end of the bell curve, you can expect your received signal be equal or better than the indicated signal strength. It is a conservative estimate (meaning the predicted signal strengths will generally be lower than reality), but I've found that it does a better job of matching my real-world expectations and measurements, as compared to the FCC's choice of F(50,90) parameters.



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while I don't think a correction(if necessary) so this tool will produce the "most accurate numbers" regarding the "raw signal" in this regard is necessary in any sense for this tool to be immensely useful+valuable, as it already is

I strongly agree. The tools are only useful if they do a good job of tracking reality. As long as the trends are all in the right direction and relative levels agree with reality, the absolute offset of the entire system hardly matters. As long as there is consistency across all the predictions, we can develop our own sense of where those receivability thresholds lie, with the understanding that this will never be an exact science.

I've provided rough receivability thresholds on the current F(99,99) scale based on years of testing in a various cities across the US. These predictions are all about statistics, so depending on where you live, time of year, and your surrounding terrain composition, the level of conservatism in the predicted signal strengths may vary. The end goal is to provide the user with a realistic expectation of which TV channels they can receive and avoid misleading the user with unreceivable channels as much as possible (I think most of the gripes about antennaweb stem from these issues).



Quote:


Indeed, as far as I can tell(which admittedly is nothing too detailed), with possible exception regarding the "exact" Dbm values, currently ..... Andy's software(the coverage maps+this tool) do seem to me to be roughly equivilent to the "FCC predictions" involving the service area contour maps available at FCC's TV query. As well as involving Longely-rice studies submitted by stations to FCC per their requirements. the latter which can sometimes be dug up as PDF attachements to applications the stations file with FCC, or via comments submitted regarding various FCC proceedings.

But, I think, as has been mentioned by others, where the use of contour methodology and the use of HAAT as an important factor fails involves matters regarding local terrain issues. For instance, regarding HAAT only -- the coverage area not only is usually much larger than the distance from transmitter site for which the terrain height is "measured" for the HAAT by FCC requirements, the terrain at any given receive location within the entire coverage area can of course vary greatly as well .....

It's always good to keep in mind that the modeling parameters and many of the FCC policies were created during a time when terrain data and computer horsepower was far more limited than it is today. Part of the reason behind HAAT approximations and F(50,90) curves/lookup tables was to reduce the number of computations necessary to come up with coverage areas and interference keep-out zones. It was impractical to actually compute detailed terrain profiles and go through propagation modeling computations on-the-fly like we do today.

We have to thank NASA and JPL for the recent introduction of highly detailed and accurate terrain data. And we should thank Intel and AMD for pushing the envelope for better processing power. Each radar plot analysis loads hundreds of megabytes of terrain data (entire North American data set is over 9 GB), loads several megabytes of transmitter data, and runs through millions of computations in the Longley-Rice modeling. Even just 10 years ago, this kind of analysis could only be done one the world's best supercomputers. Today it can be done in a matter of seconds on a high-end desktop PC.

We can do a lot better now than the FCC did 50 years ago, but they did a decent job given the available tools of that era. Unfortunately, it will probably take a long time before the FCC migrates to better tools since there's so much legacy there. Heck, I'm still amazed that they use the NAD27 as the primary datum in their database when the whole world seems to have moved on to WGS84 or later datums.



Best regards,
Andy
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post #93 of 654 Old 05-30-2007, 03:33 AM - Thread Starter
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Quote:
Originally Posted by Nitewatchman View Post

In other words, I'm saying It seems to me at this point the +10db shift Andy mentioned earlier that he might implement to make the values more realstic in the real world(based on comparisions and measurements he has taken with test equipment, not with what I have observed here, as I have no test equipment to verify the observations nor can I take "exactly" into account the factors involved with antenna system)--- or if finds a little different "shift" would be more accurate ---- AFAIK it seems to be a good idea to me ...

Just to set the record straight, yes, I did mention in a couple of previous posts that I think a +10dB shift seems appropriate to make the F(99,99) predictions do a better job of matching reality.

As a bit of background information, the FCC uses F(50,90) curves for their models. Over the decades, many people have come to realize that those predictions are roughly 10 dB too optimistic. I came to the same conclusion based on my own tests (related to my regular day job). I use F(99,99) in my tools because I felt it tracked reality better (not counting any offset). It turns out that the F(99,99) predictions seem to be roughly 10dB lower than actual measurements. The total difference between F(99,99) and F(50,90) is indeed about 20 dB under most circumstances.

One thing to keep in mind, however, is that field measurements are VERY hard to measure cleanly. When I came to the +10dB conclusion is was based on hundreds (or more likely thousands) of individual readings. The raw measurements had about a +/- 20 dB swing around anticipated signal strengths (yes, that's a 40 dB varability window). The problems are a) you can't control the RF environment and b) it's almost impossible to generate reproducable test results. Raleigh fading will easily cause about 20 dB of time-varying fluctuations. Also, since there's no such thing as a real isotropic antenna, in the real-world, we can only test with an approximation of a dipole antenna. Real-world antennas have irregularly shaped antenna patterns, imperfect impedance matching, imperfect polarization, etc. The "noise" in field testing measurements is much bigger than the resolution of the value we're trying to estimate. That's simply the reality of RF science.

By averaging/filtering lots of measurements, it's possible to find the best offset to make the predictions fit reality. I've been hesitating to do so for a few reasons:

1) Even though I've looked at lots of collected field data, it still only represents a small percentage of all possible environments. Other parts of the country under different weather conditions and seasons might be better served with a different offset. Remember that the the Longley-Rice model uses statistical tables that account for ground composition, moisture content, air density, and other factors that can vary from place-to-place, and day-by-day.

2) In the grand scheme of things, the absolute offset is not that important. Once people get used to a particular scale, consistency becomes more important. Shifting the scale arbitrarily (since it's hard to say what is really the most correct offset) might not add any value, but will certainly add some confusion, at least initially.

3) The F(99,99) model is supposed to be a near worst-case scenario, so it SHOULD produce extra conservative numbers (lower than reality). I know this isn't obvious to everyone nor does it matter to the average user, but it was the intent of the model designers to be this way. It's sort of like under-promising so that you can over-deliver (which is actually how I like to approach a lot of things). To add 10dB to the results and recast them as "average" values just muddies the water more in terms of explaining how the tools generate their results.



No matter what I do, the truth is that real-world measurement have far more variability to them than 10dB and nobody has a perfect antenna/RF chain. The unknown variables in a typical setup (impedance mismatches, connector losses, uneven gain in amps, uneven antenna gain, tuner noise figure, etc.) usually make it impossible to directly compare simulation with reality. I can't put 60 miles worth of terrain in an RF test chamber in order to validate the L-R model.


I hope that helps explain my dilemma and some of the issues involved.


Best regards,
Andy
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post #94 of 654 Old 05-30-2007, 03:51 AM - Thread Starter
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Quote:
Originally Posted by KeithAR2002 View Post

Just wondering, but when will tvfool.com be back up and running? It's been down since Saturday for me.

Yes, the site went down on Saturday around 11am. The servers were updated with the latest system patches and there were some other tweaks to try to improve processing performance even further than done previously. The systems crashed (newer is not always better!) and I was unable to restore things since I did not have access to an internet connection. The servers have been restored to their earlier state and should be running normally again.

I'm terribly sorry for the inconvenience. Having been burned enough times, I figure that by now I should've learned to avoid making big changes just before going on vacation. It just goes to show that just as rock beats scissors, stupidity can win over common sense at any time.

Best regards,
Andy
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post #95 of 654 Old 05-30-2007, 12:12 PM
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Andy,

Thanks much for all the detailed info! It's exactly what I was asking for -- as, I think if you're going to provide "numbers" regarding predicted signal strength(which btw is something I'm very glad you are doing) -- I think We (well I anyway) do really need to know how they are calculated(and it helps to know why you did it the way you did as well), and what they "mean" as much as possible in order to allow for the best, most accurate(as possible) use of them.

Especially since, as you provided great detail on -- There is really no way we can "verify" "numbers" to anything near an "exacting sense" due to a great number of factors. So, the more we know about it, the better we can utilize the "numbers", I think. with the understanding that they can be off by a fairly wide margin, for various reasons you mention.

So, In other (shorter)words, I think the more we know about what the numbers "mean" the better we can interpet them. But, To be honest, regarding that, I must say I was thrown off by your "+10db shift" comment earlier .... Thanks for clarifying that.

BTW, .... one other example of something that can throw them off --- I would suspect in some cases the numbers might even be off somewhat due to stations facilities in the real world not quite "exactly" matching the FCC records on it, even the "proper" FCC records.

Also, What is a good thing to keep in mind I think is it is just as important in some cases to consider the possibility of having too much "strong signals" as it is to consider what stations may be receivable at all .... As, there are cases when it is just as important to think "conservatively" regarding situations when there might be TOO much signal as it is to consider when there might not be enough, or might "barely" be enough ... Especially in regards to adding preamps .....


Also regarding F(99,99) curves -- Thanks for the add'l info! I certianly think you've made the right choice to "go conservative" -- I can't offer any detailed info, but generally and roughly from what I've seen so far, which seems to match your observations -- it does seem to be quite realistic, at least in my area. And, I'm also quite thankful+think it is a good idea you're also including the weaker signals in the plots that will not be recievable(or at least not very likely - such as below -110dbm or so ) ....

Couple of other comments.

Quote:
Originally Posted by Andy.S.Lee View Post

To add 10dB to the results and recast them as "average" values just muddies the water more in terms of explaining how the tools generate their results.

I agree ,based on the info you've provided ... Thanks for the clarification, and again, for All the info!

Quote:


The unknown variables in a typical setup (impedance mismatches, connector losses, uneven gain in amps, uneven antenna gain, tuner noise figure, etc.) usually make it impossible to directly compare simulation with reality.

Absolutely agree ! But, I think it is fun, when possible to some degree to "see what we get" and, when(or as much as is) possible compare what we are getting in real world with the predictions, And, fun to speculate about what may cause any differences involved.

Along those lines -- For the UHF station on 24 for which I provided an example of my "results" earlier(and along those very lines was WHY I provided it, not to even attempt to "accurately" try to measure it in any exacting sense) :

The 41dbu contour map shown at TV Query shows my location as (pretty much) RIGHT on the 41dbu/Meter contour for this station. Of course, I believe that takes into account FCC planning factors for DTV reception such as receive antenna gain of 10db on UHF, Antenna at 30FT AGL and feedline loss on UHF of 4db per 100ft of RG6. There are other "planning factors" taken into account as well(see the OET bullitin #69 I provided a link to earlier), but I think those are the most important/most significant ones involved here.

Another longely-rice study done for my location for this station and 30FT AGL receive antenna height+taking into account the FCC "planning factors"(antenna gain/feedline loss/etc) using a commercial package(a broadcast engineer friend did this for me several years ago) indicated 43Dbu/m signal strength from them at my location.

Your tool shows a -100.2dbm prediction for that station at antenna height of 35FT AGL. If I'm doing my math right - Such as using this calculator (Row 41~45 in the excel spreadsheet downloadable from this link ) for converting dbm to the Dbu/meter values FCC uses : It indicates -100.2 dbm should be equivilent to about 29Dbu/M at 530 MHZ(channel 24).

So, if we add FCC planning factors such as 10db of antenna gain+ the approx 4db of expected feedline loss to the TVFool prediction -- As it turns out in this specific case -- I believe ALL of these "predictions" turn out to be roughly the same, and within a few db or so of each other ...

And as far as I can tell* --ALL of them seem to be fairly (or perhaps Quite) accurate in this case.

* - BTW, I think AntAltMike provided a good, detailed commentary on my rough "measurement" of this specific example earlier.

What actually surprises me a bit about that is not the prediction of your tool or the other L-R study mentioned above ... It's the FCC contour, since there *are* significant terrain issues involved (in fact, I'm getting them via diffraction and it's a LONG way from being LOS), I might have thought it likely FCC would show me to be more within the 41dbu predicted contour rather than right on edge of it ....

I suppose if I were to "pretend" my rough measurement (as noted in more detail in earlier report concerning how I did it/etc) of this specific example was something near correct ... Taking antenna system(inclduing preamp gain), and losses into account regarding "how much" extra attenuation added I need to get down to just "at threshold" levels for reception(about 16db C/N for all DTV receivers) --- which of course is a measurement which is *very* reliant on not having uncorrectable multipath(can only guess about that) or other "impariment" issues(interference, IMD/etc) ... :

Again Along the lines of AntAltMike's commentary about it, and again "just pretending" my rough "measurement" is somewhat,roughly accurate : If anything, it would seem in this case that all 3 of those different predictions seem VERY accurate .... But, I think that's probably just a "coincidence", as for instance, there are all the nearby trees in signal path involved(including the "wood" part of the trees that's there year around) which I would think should involve some quite significant attenuation that is not being modeled by any of those predictions .....

Jeff
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post #96 of 654 Old 05-30-2007, 01:13 PM
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Quote:
Originally Posted by Nitewatchman View Post

So, if we add FCC planning factors such as 10db of antenna gain+ the approx 4db of expected feedline loss to the TVFool prediction -- As it turns out in this specific case -- I believe ALL of these "predictions" turn out to be roughly the same, and within a few db or so of each other ...

Ok ... At this point Looks like I may have made a mistake above regarding interpetation of FCC OET bullitin 69 although I can't say I'm quite certian of that at this point :

I was thinking that FCC's contour methodolgy, or alternate L-R methodolgy-* was *specified* to take into account the "planning factors" for DTV reception which define the field strentgh values for minimum thresholds for DTV reception(that which defines the predicted "service area" of the stations per FCC terms - 28dbu/M for lo-VHF, 36dbu/M for Hi-VHF, 41dbu/M for UHF) ...

* - As specifed as used by FCC or in various FCC rules as allowable(using F50,90 curves and antenna height above ground/etc) for use as "compliant" with FCC guidelines to evaluate service area of stations/etc, regarding their submissions/applications and such to FCC regarding such matters -- see FCC's OET bullitin #69 I provided link to earlier for more info ...

In other words, I thought a 41dbu/M "prediction" of field strength from the "station" using FCC guidelines already took, for instance 10db UHF recieve antenna gain into account as it relates solely to the "field strength" from the station, as if it were a variable that was required to be Added to the predicted field strength results from such a "FCC complaint" L-R study ... Such as that, the "field strength" may *really* be predicted to be 31dbu/M, but the +10db was *already added* into the equation, solely just for the *prediction*, because we already assume the user has 10db receive antenna gain on any given UHF frequency(yeah right!) ..

But, after reading it again, as well as Andy's comments again regarding his tool and using F99,99 curves being roughly 10db or so more "conservative" than FCC "estimates" --- I think at this point I was wrong about that, and that instead, the planning factors(10db gain on UHF, 15db SNR for DTV receiver, 4db loss in feedline/etc) instead only specifies FCC's definition of what constitues their idea of actual, minimum field strength necessary for reception in order to define service area for reception, rather than having anything to do with the field strength "prediction" ... Is that correct?

I guess part of my interest in this is because over the years of pouring through various documents from FCC, and coverage maps using the FCC specified L-R or contour methodology as submitted to FCC by stations regarding various matters concerning their coverage areas, and via using FCC's TV query site and several other tools(such as the "old" ardman signal prediction site which specified values in Dbu/M) : I've become extremely accustomed to "their way" of doing things, and involving what, I have for instance I think a good feel of what "41dbu Contour" is as related to a stations "fringe" service area .... As in, generally, you need a fairly decent outdoor directional antenna system to have a good shot at receiving a station with 41dbu/M strength ... Which of course, is EXACTLY what it's based on, it seems to me .... And as I've noted earlier, seems to me the "FCC specified" 41dbu "contours" as available in maps at TV query(or various coverage maps submitted by stations to fcc I've seen) DO seem to be roughly equivilent to the "services" areas as predicted by andy's tools(such as purple area from the Google 3D maps) .... Only with a bit different "numbers" involved, I suppose ....

Jeff
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post #97 of 654 Old 05-30-2007, 01:26 PM
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Andy,

This is a useful piece of work, giving me some ideas on trying to receive additional channels beyond the standard Houston based stations. Results are not surprising for this area, given the flat terrain and tall transmission towers - strong signals probably explain why I can get fairly reliable reception even in my Techshield attenuated attic.

I did find the radar plot difficult to read, probably due to the high concentration of transmitters in one area (SW Houston); not sure how to improve it, but offering up the observation.

Have also experienced intermittent problems accessing parts of the site (seemingly random).
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post #98 of 654 Old 06-02-2007, 05:27 PM
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Looks like the word about Andy's excellent work on this is getting out there -- Pete Putnam makes a mention of these tools+the website in this recent article :

http://www.hdtvexpert.com/pages_b/Re...TheFringe.html

Jeff
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post #99 of 654 Old 06-21-2007, 06:52 PM
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I have noticed that there are cases when the tvfool calcualtion may show that a particular location has 1 edge of refraction and then displays that the height to LOS is something like 27 feet. Next, if I enter 30 feet as the antenna height, the display goes to LOS and the signal strength jumps many db.

I was under the impression that the antenna height for the FCC Longley-Rice calculation is 30 feet. Am I wrong, or is there an explanation for the apparent discrepancy?
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post #100 of 654 Old 06-21-2007, 10:48 PM - Thread Starter
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Quote:
Originally Posted by Tower Guy View Post

I have noticed that there are cases when the tvfool calcualtion may show that a particular location has 1 edge of refraction and then displays that the height to LOS is something like 27 feet. Next, if I enter 30 feet as the antenna height, the display goes to LOS and the signal strength jumps many db.

I was under the impression that the antenna height for the FCC Longley-Rice calculation is 30 feet. Am I wrong, or is there an explanation for the apparent discrepancy?

Excellent question!

I probably should have explained this somewhere, but then I didn't want to throw a lot of details out there and distract from the "just plug in an address and go" simplicity of the tool. Here's the detailed explanation of what's going on...



If you leave the height field blank, the analysis will automatically pick a height for you. The height it uses depends upon how accurate it thinks it's resolved your location.

For example, if you've entered an exact address, the tool will use a height that's roughly equivalent to the first floor of a house. If you only enter only a zip code, the tool will use a height that is approximately 100 feet above ground.

This way, if a user enters nothing but a zip code, they will see enough channels to give them a rough idea of what's available in their neighborhood (and avoid being influenced by small terrain variations). If a specific address is given, the analysis will more accurately represent the signals just outside their house (including any local terrain effects).

If you enter a height value manually, you can override this automatic behavior.

Best regards,
Andy
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post #101 of 654 Old 06-22-2007, 08:13 AM
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Thank you for the explanation and the fantastic calculation tool.

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Originally Posted by andy.s.lee View Post

Excellent question!

I probably should have explained this somewhere, but then I didn't want to throw a lot of details out there.

If you enter a height value manually, you can override this automatic behavior.

Best regards,
Andy

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post #102 of 654 Old 08-01-2007, 09:22 AM
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Thanks to Andy for the wonderful tools he has provided.

Any idea on when Paducah/Cape G, and Hannibal/Quincy might be added? Those are the last two holes around my own market (STL).
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post #103 of 654 Old 10-29-2007, 12:57 AM - Thread Starter
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The radar plots now include magnetic north readouts for all of you who are using a compass to point your antennas. The plot itself now has a red "N" showing the direction of magnetic north. Your compass needle will point toward this "N" and you should be able to get your bearings that way. Exact azimuth readings are also included in the details for each transmitter.

I hope this helps!

Best regards,
Andy
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post #104 of 654 Old 10-29-2007, 07:29 PM
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Nice add. Personally, I'd add a vector from center to show a true compass "arrow", but then it would clutter the already small plot area.

Nit: Please check your form layout on the data entry screen. The address, city, state forms line up crooked to the left of the title. When I enter the state, the lines jump to the right to align with the title.

Backgrounder: Magnetic declination (compass correction) can be calculated via zip code / lat /lon at the NOAA Geophysical Data Center: http://www.ngdc.noaa.gov/seg/geomag/...alcDeclination
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post #105 of 654 Old 10-30-2007, 01:25 AM - Thread Starter
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Quote:
Originally Posted by GeekGirl View Post

Nice add. Personally, I'd add a vector from center to show a true compass "arrow", but then it would clutter the already small plot area.

Nit: Please check your form layout on the data entry screen. The address, city, state forms line up crooked to the left of the title. When I enter the state, the lines jump to the right to align with the title.

Backgrounder: Magnetic declination (compass correction) can be calculated via zip code / lat /lon at the NOAA Geophysical Data Center: http://www.ngdc.noaa.gov/seg/geomag/...alcDeclination

GeekGirl,

Thanks for the feedback!

I was debating how to best indicate magnetic north on the plot, but nothing's perfect. I was actually thinking of drawing a mini bar magnet in place of the "N", but it might have been hard to figure out what the hell I was drawing, so I stuck with the plain and simple.

Additional arrows/crosshairs/etc. were also considered, but then I decided that having that much visual detail (and clutter) hardly helps anyone point their antenna. The plot provides a good general orientation, but it's the numeric azimuths in the table that end up being important. I thought that keeping it as simple as possible was the best first pass and I'll let everyone voice their opinions if they feel strongly otherwise.

It's a good suggestion and was honestly considered while writing the code.



As for the alignment issue, this seems to be a bug in Mozilla/Firefox. I tried variations on the HTML, but Mozilla is insisting on rendering the screen with "auto" column width on the first rendering pass. It's not until you hit the state drop-down list that it finally realizes that a different width was requested.

I might be possible to fix/hack by using HTML 4.01 formatting tags, but that would be a bit of a step backwards as the page is currently XHTML Transitional compliant. I'd prefer to be compliant with current and future standards rather than go backwards.

Internet Explorer seems to render this correctly on the first draw and I have yet to test this on other browsers, but ultimately I think this is a bug that Mozilla needs to fix. It's not a show-stopping bug, but it's annoying, nonetheless. Suffice it to say that it's not easy to make a web site render well on a wide range of browsers.



Although we all remember that a compass points north, it's actually interesting to know just how far off it can be depending on where you are (+/- 20 degrees or so for most of the continental US). Also, most people don't realize that the magnetic pole has been moving at a rate of over 40 km per year.



Again, thanks for all the great feedback!

Best regards,
Andy
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post #106 of 654 Old 10-30-2007, 12:29 PM
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Andy, Just a FYI ..In case it's of any use to you ...

Seems to be some odd new errors in FCC database recently involving LP analog stations in my area, which are also "reflected" in tvfool plots for my area ... I don't know if these are just rare "oddities" which are specific only to these stations records, or if something more "widespread" is involved, but again just a heads up FWIW ...

Descrptions below :

WRCX-LP 40 Dayton ... Certianly still on air, but no record for WRCX-LP (or any other callsign which might correspond to this LP station in Dayton Ohio) currently shows up in FCC's TV query, or CDBS Application search, nor any longer in tvfool plots (They did show up in TVfool plots for my area as recently as a week or two ago) .. Also, Their records *did* show up in FCC info as recently as a week or so ago .. Weird ...

WWRD-LP Dayton -- Shows up with a incorrect callsign of "DWWRD" ... Note: wouldn't expect this to be shown in TVfool plot until their license to cover app is granted by FCC, but, BTW, They moved from channel 55 to channel 32 in Early October+have filed a license to cover app on 32 with FCC, which according to FCC records has not been granted as of yet ... Note that in the application for "license to cover", they say the ERP in actuality is "lower" and isn't as stated in the CP because they can't get enough A/C power into the transmitter shack, yet .... Which seems odd to me, as it would seem to me they'd probably need an STA (on 32) for that ...

W66AQ Dayton - Currently operating Licensed facilities on channel 66 (and is shown as "should be" in TVfool"), but also has a CP to move to channel 22/repurpose WKEF 22 analog's existing facilities after analog shut off on 2/17/09 ... The application/authorization info is still present for the 22 CP at FCC site -- however, when it was an application(before the CP was granted), it also "showed up" in FCC's TV query results, which is no longer the case (Who knows, maybe because WKEF 22 is currently a full service analog station operating on channe 22 in Dayton ? )

Must admit, The way FCC "handles" these records in CDBS are sometimes quite a mystery to me ...

Some other "ongoing" oddities in my area that aren't "recent" also include "license to cover" apps submitted by WKEF-DT and WRGT-DT in 2005, which still don't show up as "granted" by FCC in CDBS application info, therefore they "show up" in TV query as CP's only, along with STA's those stations have been operating with ... (think I recall you must have "fixed those" manually, as the correct ERP's are shown in TVfool for the CP rather than the STA/etc) ....

Jeff
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Quote:
Originally Posted by Nitewatchman View Post

Andy, Just a FYI ..In case it's of any use to you ...

Seems to be some odd new errors in FCC database recently involving LP analog stations in my area, which are also "reflected" in tvfool plots for my area ... I don't know if these are just rare "oddities" which are specific only to these stations records, or if something more "widespread" is involved, but again just a heads up FWIW ...

Descrptions below :

WRCX-LP 40 Dayton ... Certianly still on air, but no record for WRCX-LP (or any other callsign which might correspond to this LP station in Dayton Ohio) currently shows up in FCC's TV query, or CDBS Application search, nor any longer in tvfool plots (They did show up in TVfool plots for my area as recently as a week or two ago) .. Also, Their records *did* show up in FCC info as recently as a week or so ago .. Weird ...

WWRD-LP Dayton -- Shows up with a incorrect callsign of "DWWRD" ... Note: wouldn't expect this to be shown in TVfool plot until their license to cover app is granted by FCC, but, BTW, They moved from channel 55 to channel 32 in Early October+have filed a license to cover app on 32 with FCC, which according to FCC records has not been granted as of yet ... Note that in the application for "license to cover", they say the ERP in actuality is "lower" and isn't as stated in the CP because they can't get enough A/C power into the transmitter shack, yet .... Which seems odd to me, as it would seem to me they'd probably need an STA (on 32) for that ...

W66AQ Dayton - Currently operating Licensed facilities on channel 66 (and is shown as "should be" in TVfool"), but also has a CP to move to channel 22/repurpose WKEF 22 analog's existing facilities after analog shut off on 2/17/09 ... The application/authorization info is still present for the 22 CP at FCC site -- however, when it was an application(before the CP was granted), it also "showed up" in FCC's TV query results, which is no longer the case (Who knows, maybe because WKEF 22 is currently a full service analog station operating on channe 22 in Dayton ? )

Must admit, The way FCC "handles" these records in CDBS are sometimes quite a mystery to me ...

Some other "ongoing" oddities in my area that aren't "recent" also include "license to cover" apps submitted by WKEF-DT and WRGT-DT in 2005, which still don't show up as "granted" by FCC in CDBS application info, therefore they "show up" in TV query as CP's only, along with STA's those stations have been operating with ... (think I recall you must have "fixed those" manually, as the correct ERP's are shown in TVfool for the CP rather than the STA/etc) ....

Hi Jeff,

Thanks for all the update details!

I'm not sure what to do about these as of yet. My preference would be to fix the data so that it's the best possible representation of what is "real" today. If it's possible to know the correct FCC record that represents the real status, that would be the easiest to patch.

Another option is to wait and hope that the FCC database catches up with reality and fixes all the errors, but there's no telling how long that will take.



BTW, it looks like the WRCX facility license was recently cancelled (on 10/15/2007) and that's why it's no longer showing up in any of the FCC and TV Fool lookups. Here's the FCC info on that facility: http://svartifoss2.fcc.gov/cgi-bin/w...ility_id=69535

If they are still on the air, then they might be doing so illegally.



'Tis true that the FCC database is a mess in some places, but with everyone's feedback here, we can try to stay a half step ahead of them.



Best regards,
Andy
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Quote:
Originally Posted by andy.s.lee View Post

BTW, it looks like the WRCX facility license was recently cancelled (on 10/15/2007) and that's why it's no longer showing up in any of the FCC and TV Fool lookups. Here's the FCC info on that facility: http://svartifoss2.fcc.gov/cgi-bin/w...ility_id=69535

Wow! Thanks for posting that link, I had searched for any info on them via the CDBS searches available from following link, yesterday, but didn't find anything -- Trying it again, I see the reason why I didn't find that was because I was searching for "WRCX-LP" instead of "DWRCX-LP" !!!!! ... Is the "D" added to the callsign perhaps indication that license has been cancelled??? ....

http://svartifoss2.fcc.gov/prod/cdbs...od/cdbs_pa.htm

Hmm ... Ok, this is interesting, "DWWRD-LP" dayton *also* shows that it's license was cancelled on 10/15/07 , see here :

http://svartifoss2.fcc.gov/cgi-bin/w...ility_id=17237

I also searched through Daily digests(the broadcast actions files/etc) for 10/15 and several days before hand, as well as doing a "specific" search of entire FCC site of WRCX/WWRD/etc, and could not find any info on the license cancellation ! Weird!

Quote:
If they are still on the air, then they might be doing so illegally.

While WWRD-LP doesn't appear to currently be on air from what I can tell from my location, on 32 or 55 (I did receive them on 55 when they were operating there up until a few weeks ago or so) ...

WRCX-LP is defintely still on air ... Attached farther below is screenshot of them via OTA from This evening around 6pm EDT (sorry about the poor quality/ghosts/etc) ... Their website is still up as well :

http://www.wrcxtv40.com/

-----------------

Update : OK -- after some more investigation, think I now know what is going on ... As the "lic expired" info shown for both WWRD-LP and WRCX-LP in the "license cancelled info" indicates both of these stations licenses expired on 10/1/2005, and apparently (I can't find them anyway) they did not file for license renewals!

In more detail, Concerning WRCX-LP (Much the "same thing" is the case concerning WWRD-LP) to explain a bit how I "doubechecked" to see if the lic expired info shown in the "licensed cancelled" info is correct ...

So, The "license cancelled" info in link you provided for WRCX-LP indicates their license expired on 10/1/05 ... However, They were granted a "license to cover" their current operation on channel 40 in feburary 2004, see here :

http://fjallfoss.fcc.gov/cgi-bin/ws....tion_id=972435

However, If you click on the "view authorization" link at the above link(I don't think I can provide a direct link to it), and pull up the authorization, IT also shows that their license expired on oct 1, 2005! (Note: the same is true for WWRD-LP "last" authorization I could find, which also shows a license expiration date for them of 10/1/05) ---

----------------------------------------------------
LL

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Quote:
Originally Posted by Nitewatchman View Post

Wow! Thanks for posting that link, I had searched for any info on them via the CDBS searches available from following link, yesterday, but didn't find anything -- Trying it again, I see the reason why I didn't find that was because I was searching for "WRCX-LP" instead of "DWRCX-LP" !!!!! ... Is the "D" added to the callsign perhaps indication that license has been cancelled??? ....

http://svartifoss2.fcc.gov/prod/cdbs...od/cdbs_pa.htm

Hmm ... Ok, this is interesting, "DWWRD-LP" dayton *also* shows that it's license was cancelled on 10/15/07 , see here :

http://svartifoss2.fcc.gov/cgi-bin/w...ility_id=17237

I also searched through Daily digests(the broadcast actions files/etc) for 10/15 and several days before hand, as well as doing a "specific" search of entire FCC site of WRCX/WWRD/etc, and could not find any info on the license cancellation ! Weird!



While WWRD-LP doesn't appear to currently be on air from what I can tell from my location, on 32 or 55 (I did receive them on 55 when they were operating there up until a few weeks ago or so) ...

WRCX-LP is defintely still on air ... Attached farther below is screenshot of them via OTA from This evening around 6pm EDT (sorry about the poor quality/ghosts/etc) ... Their website is still up as well :

http://www.wrcxtv40.com/

-----------------

Update : OK -- after some more investigation, think I now know what is going on ... As the "lic expired" info shown for both WWRD-LP and WRCX-LP in the "license cancelled info" indicates both of these stations licenses expired on 10/1/2005, and apparently (I can't find them anyway) they did not file for license renewals!

In more detail, Concerning WRCX-LP (Much the "same thing" is the case concerning WWRD-LP) to explain a bit how I "doubechecked" to see if the lic expired info shown in the "licensed cancelled" info is correct ...

So, The "license cancelled" info in link you provided for WRCX-LP indicates their license expired on 10/1/05 ... However, They were granted a "license to cover" their current operation on channel 40 in feburary 2004, see here :

http://fjallfoss.fcc.gov/cgi-bin/ws....tion_id=972435

However, If you click on the "view authorization" link at the above link(I don't think I can provide a direct link to it), and pull up the authorization, IT also shows that their license expired on oct 1, 2005! (Note: the same is true for WWRD-LP "last" authorization I could find, which also shows a license expiration date for them of 10/1/05) ---

----------------------------------------------------

According to this link, http://svartifoss2.fcc.gov/prod/cdbs...t_letter_id=90, it looks like the reason WRCX's application was declined may have been due to interference with WHIZ in Zanesville, OH.

Best regards,
Andy
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While it would be something of a departure from the site's main tuning/reception theme, suggest adding a video-signal analysis section. This would include computer software packages that permit spectrum analysis of HD luma, such as the free shareware (trial)/low-cost software AVSer dr1394 outlines here . dr1394 provides a sample analysis chart of a 720p crowd scene in the following thread post. Spectrum analysis, applied to RF rather than luma, AIUI, can be useful for station tuning, too. Part of this add-on section might cover standard bit-rate analysis software tools, too. The luma spectrum analysis, if refined enough, might aid PQ comparisons between station main HD channels and subchannels. Yup, there's apparently so little practical material available on luma S.A. of HDTV that this all might be more of a SF proposal. :-) -- John
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Quote:
Originally Posted by andy.s.lee View Post

According to this link, http://svartifoss2.fcc.gov/prod/cdbs...t_letter_id=90, it looks like the reason WRCX's application was declined may have been due to interference with WHIZ in Zanesville, OH.

Best regards,
Andy


Looks like portions of FCC site are down right now+I can't provide the link(s), but I believe that (the "imported letter" about the WHIZ interference) actually involves a CP MOD application WRCX submitted, later -- File # BPTTL-20040406ABW. It was an app for a CP mod to make some further changes to their facilities, If I recall correctly, mostly involving change in transmitting antenna height/location ... That application was dismissed by FCC in 2006 due to the reasons stated in that letter (a link to that letter is also attached to the "info" on that specific application ) ...

The early feburary 2004 "license to cover" application however, (File # BLTTL-20040203ABQ ) from WRCX I reffered to earlier involves a "different" CP they already had, and the license to cover THAT CP was granted by FCC+doesn't involve that letter or the CP modification applied for in that CP mod app which was dismissed by FCC in 2006 as mentioned above ....

So, the "license to cover" application+it's "granted status" from FCC involves the facilities they've been operating with since 2004, including currently... Since it's the only thing they have(well, had at least until 10/1/05) a "license" for, it would seem to me the "cancelled license" should apply to this rather than the "dismissed" CP Mod involving the WHIZ interference issue, which was never granted by the FCC, anyway ... Note that WRCX was on channel 51, and was displaced by WKEF-DT in Early 2002 -- It took them a couple of years to get the CP for channel 40 and get back on the air in late 2003 or early 2004(on ch 40) .....

When those "portions" of FCC site are back up, you should be able to use the CDBS "application search"(instead of the station search page) page. By searching either using their facility ID or "DWRCX-LP", all their applications since the 1980's or so should "show up" if you select all the appropraite selections(application types/status/etc - I'd just select them all) from the 'drop down boxes" for the search. They did show up yesterday anyway, and the info+links which should be available for all of those should hopefully make things at least somewhat clearer If I haven't explained it very well, which is probably likely


Update:

Ok, that portion of FCC website is back up and I Found the info ....

Info on the dismissed CP MOD application (BPTTL-20040406ABW), which was filed in 4/2004, and dismissed by FCC in June 2006 :

http://fjallfoss.fcc.gov/cgi-bin/ws....ion_id=1007244

click on "Correspondance folder" and you'll get the same info on the letter/link to it ...


Here is the application itself which was dismissed because of the WHIZ interference (note: looks like some amendments to this app were made since I last recall looking at it) .... :

http://fjallfoss.fcc.gov/cgi-bin/ws....ility_id=69535


----------------------

But, here is the info on the "License to cover" (# BLTTL 20040203ABQ which was filed to "cover" the CP which was file # of BPTTL-20011213ABD ) and which was granted by FCC in Feb 2004 :

http://fjallfoss.fcc.gov/cgi-bin/ws....tion_id=972435

The actual application itself is here :

http://fjallfoss.fcc.gov/cgi-bin/ws....ility_id=69535

Jeff
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A couple ideas I have for TV Fool:

1) Sorting by channel number, call sign and/or direction
2) Adding the 2009 channels (though these are only available on full power stations at this point)

I sent these to Andy already, but thought I should post them here for reference.

I have found TV Fool to be the most effective resource for determining prospects for reception and I will look forward to future upgrades (as time permits of course).

Thanks so much, Andy!


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In case anyone is interested, yesterday, I finished downloading the entire TV Fool database file covering all of the individual files. I really don't plan on using all of it. In fact, I probably won't use much of it. I have a 1.5 mega bit fiber internet connection and the download took approximately 23 hours. I only downloaded when I wasn't using the internet for other things to allow full bandwidth use.
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Quote:
Originally Posted by Nitewatchman View Post

Hmm ... Ok, this is interesting, "DWWRD-LP" dayton *also* shows that it's license was cancelled on 10/15/07 , see here :

http://svartifoss2.fcc.gov/cgi-bin/w...ility_id=17237

Quick update on that one ...

In early Novemenber DWWRD-LP filed for a legal STA, in exhibit 38 attached to application it says they want STA because of FCC cancelling their license in Mid-october due to their failure to file a renewal application by June 1, 2004. It also says they have recently "engaged counsel" to assist them with filing a license renewal application ... :

Here is the "info" on the STA app via CDBS search page :

http://fjallfoss.fcc.gov/cgi-bin/ws....ion_id=1216783

And here is the application itself :

http://fjallfoss.fcc.gov/cgi-bin/ws....&fac_num=17237

So, OK, that makes sense, and it makes sense that WWRD-LP does not seem to be on air currently/since their license was cancelled(from what I can tell anyway, I did receive they were operating on 55 up to a little over a month or so ago)

But, What still seems odd is that "DWWRD-LP" still shows up in FCC's TV query (and TVfool plots), but "DWRCX-LP" does not. Even though WRCX-LP seems to be 'experiencing' a similar, if not identical situation --- although they are still on air, and apparently have not filed for a STA or license renewal -- at least one that shows up in CDBS search(their other application/etc. do show up via a search for "DWRCX-LP on CDBS search page ....

-------------------------------------------------------------

Quote:
Originally Posted by andy.s.lee View Post

'Tis true that the FCC database is a mess in some places, but with everyone's feedback here, we can try to stay a half step ahead of them.

Most definitely ... I think one of the things that makes TVfool very useful is it's accuracy involving the facilities stations are using.

Perhaps we'll especially want to keep a close eye on it regarding digital stations which will be moving to different channels after analog shut off .... Haven't seen any CP's pop up for any of those in my area yet, but I'd think that might start happening soon ....

Also wonder what will happen regarding the records for all the analog full service stations around 2/18/09 ....

Jeff
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I have a question on the Xmit(kW) column on the output. I know that it takes into account the directional patterns of the transmitting antennas. However, plugging in the raw ERP from the FCC's website times the polar plot factor, I'm coming up with lower numbers. Are the FCC polar plots non-linear or am I doing something else wrong?


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Originally Posted by Falcon_77 View Post

I have a question on the Xmit(kW) column on the output. I know that it takes into account the directional patterns of the transmitting antennas. However, plugging in the raw ERP from the FCC's website times the polar plot factor, I'm coming up with lower numbers. Are the FCC polar plots non-linear or am I doing something else wrong?

The polar plots on the FCC web site are based on voltage. You may square the values to get relative power, or use the voltage db formula (20*log V) for answers in db.
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Also be sure to take into account any pattern rotation shown.

The graphical polar plots on FCC site take any pattern rotation into account, but the text figures listed in TV query don't you have to add the pattern rotation value(which is also shown in degrees) ...

As Tower Guy said, "you may square the values to get relative power" .... For convienience, A formula for figuring ERP sent in your direction from the relative field values shown on FCC site is :

Relative field value(for your direction) squared x ERP for a relative field value of 1.000 = ERP sent in your direction ..

For example, given a relative field value of say, .190 in your direction, and ERP of 512KW ERP shown for their operating permit it would be :

(.190x.190) x 512,000(watts ERP) = 18,483.2 Watts ERP sent in that direction ...

Of course, the Tvfool Xmit(Kw) column does this for you, probably in a more accurate way since the relative field values are only listed in 10 degree increments ...

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Great. Thanks for the help.

I noticed pattern rotation on one transmitter. After I wrote the above message, I saw that it says "relative field values," so presumably that would mean relative net dBu strength, right?

Also, from the research I've done, it seems that the simple 5x for digital ERP is not quite sufficient to match "effective" digital power vs. analog power. Or rather, perhaps it is better to state that digital signals can be received at weaker dBm levels than analog. Converting the FCC's service grade specs to dBm yields about -65dBm for analog and -85dBm for digital for a service area. TV Fool seems to allow 10dBm for this on the chart. i.e. -100dBm and below is gray on analog and -110dBm on digital.

I am trying to ascertain the probability of reception at a site after 2009 and TV Fool does not yet have 2009 data in the output. Of course, the FCC doesn't have much of this data itself yet, so it is more conjecture at this point (at least we have the max ERP's).


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post #119 of 654 Old 11-16-2007, 08:53 PM
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Quote:
Originally Posted by Falcon_77 View Post

After I wrote the above message, I saw that it says "relative field values," so presumably that would mean relative net dBu strength, right?

The way I understand it (FWIW) :

DBu(dBµV/m) (electric field intensity) is decibels above one microvolt/meter (dBµV/m). It's something that changes as you move farther away from transmitter site and involves things such as transmitter output power/antenna gain/antenna pattern/etc.

I think of The relative field values as "describing" the antenna's pattern, with values allways between 0 and 1. A value of "1" would equate to the antenna's maximum gain (main lobe) in Dbi or DbD.

In other words, the relative field values shown on FCC site "describe" the transmitting antenna's directional pattern while "limiting" the values to values between 0 and 1 rather than expressing the values for the polar plot in dbi or dbD ...

In additon to Tower guy's post involving using (20 * log V) to convert the relative field values to Db units(decibel units are logarhythmic), you might want to read the text under "figure 2" here :

http://www.softwright.com/faq/engine...Y%20UNITS.html

BTW, FCC's OET bullitin 69 (think I provided link to it earlier in thread) also says this about the relative field values :

"In cases where the TV Engineering Data Base indicates that a directional antenna is employed, the ERP in each specific direction was determined through linear interpolation of the relative field values describing the directional pattern. (The directional pattern stored in the FCC Directional Antenna Data Base provides relative field values at 10 degree intervals and may include additional values in special directions. The result of linear interpolation of these relative field values is squared and multiplied by the overall maximum ERP listed for the station in the TV Engineering Data Base to find the ERP in a specific direction.)"

Also, FCC provides some handy calculators (including Relative field values to ERP so you don't have to do the "manual" calculation I provided earlier) here :

http://www.fcc.gov/mb/audio/bickel/findvalues.html

Quote:


Or rather, perhaps it is better to state that digital signals can be received at weaker dBm levels than analog.

Genearlly, I think, Yes, at least if you are talking about relatively "snow-free" NTSC signals. There are several "reasons" why ... One is that DTV power is measured as "average" power, NTSC is expresssed as "peak" power. Another as I understand it is threshold for DTV reception with our receivers can be achieved with signifcantly less signal than it takes to acheive a "non-snowy" analog picture. I can't recall what that "exact" difference is don't hold me to this, but thought I'd read somewhere it was about a 12db difference.

Although, my experience is you can receive/detect or "see" a extremely weak ("snowy") analog signal "above the snow" with signal levels well below those as defined by for the grade B "service contour". I expect probably even below what is needed for threshold DTV reception, at least based on my "rough" and non-verifyable observations that seems to be the case ...

Anyhow, Among other things "related" to your post+inquires, You'll find the values for the "service contours" FCC uses (in Dbu) listed for DTV/analog here.

http://www.fcc.gov/mb/audio/bickel/curves.html

You might also find info in this article useful :

http://www.tvtechnology.com/features...Coverage.shtml

Quote:


Converting the FCC's service grade specs to dBm yields about -65dBm for analog and -85dBm for digital for a service area.

That's pretty close to what I get for UHF Using the ".8 Convert dBm to Filed strength in dB/u and mv/meter" option in the RF calculator/excel spreadsheet available here :

http://www.rfsolutions.com/rfcalc1.htm

Using a mid-UHF band freqency of about 600MHZ I get :

-89.5dbm = 41dbu (FCC defined service countour for UHF DTV)

-66.5dbm = 64dbu (FCC defined grade B service contour for UHF analog full service stations)

*Do* keep in mind that the FCC service contour "specs" take into account "FCC planning factors" regarding such things as receive antenna gain, feedline loss and receiver noise figure, presumably with the typical equipment a consumer would be utilizing. There is info in FCC OET bulletin #69 on this as well, as discussed earlier in this thread), whereas TVfool predictions isn't "accounting for" things such as antenna gain (which I personally think is a *good* thing) ....

For DTV, taking into account these "planning factors" seems fairly straightfoward .... For instance on UHF, assuming my conversion from 41dbu noise limtied service contour = -89.5dbm is correct, I believe 41dbu "works out" to being fairly close to equaling threshold level for DTV reception if we "factor in" the FCC planning factors in a fairly conservative way along with typical NF of DTV receiver (approxmiately). As we need:

-106.2dbm (thermal Noise floor) + 15db S/N(planning factor for required carrier/noise ratio) + 7db(planning factor for estimate of receiver's noise figure) = - 84.2dbm -- w/o use of a preamp with a lower noise figure, As a "Conservative" Minimum signal level at receiver input required for DTV reception ...

So, for UHF 41dbu/-89.5dbm we "add" 10db of antenna gain and we actually now have -79.5dbm at antenna terminals, but now, we have to subtract the FCC "planning" factor for loss in the Feedline(coax), which is -4db on UHF , then we are "at" -83.5dbm at the receiver input, only +.7db "more" than our required minimal signal level at receiver input ....

I'm not sure how such a "equation" works out for analog, as although I believe the FCC planning factors for antenna gain/feedline losses are the same, If I recall correctly I think they use a "assumed" 10db noise figure for the receiver, and most importantly, I don't know what signal level at input of receiver "exactly" equates to what I'll call a "snow free" analog picture ....


Quote:


I am trying to ascertain the probability of reception at a site after 2009 and TV Fool does not yet have 2009 data in the output. Of course, the FCC doesn't have much of this data itself yet, so it is more conjecture at this point (at least we have the max ERP's).

I think in many/most cases The 2009 "data" will be the same as most stations current licensed DTV operations -- exceptions are stations that will be "moving" to a different channel(often their current analog channel). And there certianly is a significant number of those. Can't remember exactly at this point and am getting too "lazy" tonight to look it up, but I think it's around 500 or so stations are moving - I think the info on that is posted somewhere in DTV table of allotments thread in reception area ....

Other than what info is currently specifed in the "new" DTV table of allotments(I assume that's what you're looking at) I don't think we'll have the hard "data" on those facilities for those stations which will be moving until they file for Construction permits(and FCC grants them) for their new DTV facilities. You'd think those would soon be "showing up" in FCC database, given we're only 15 months, 1 day, 7 minutes away from analog shut off for full service stations at time of this post ...

I'd think "Theoretically", in most cases, the "current situation" for the TVfool prediction for the analog station involved *should* be the same (or at least roughly similar) to what will be the case for the digital station that's moving to that channel after analog shut off, as the DTV stations service area is (again generally and roughly) *supposed* to match the analog ... And I'd think you might be better off to use that as a "estimation" until the DTV station info gets into FCC database (and TVfool as well) ... Hopefully that will happen by 2/18/09 ... OTOH, there may or will be some exceptions to that ...

Jeff
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I posted a spread sheet comparing TVFOOL's RX_dBm signal levels,
to those calculated by RADIO MOBILE:
http://www.avsforum.com/avs-vb/showt...&#post10961518
http://www.avsforum.com/avs-vb/showt...&#post10961464
http://www.avsforum.com/avs-vb/showt...&#post10182808

Note that TVFOOL reportedly calculates F(99,99) statistical confidence levels,
meaning it finds the signal level (RX_dBm) that is exceeded at 99 percent of possible
"locations" for 99 percent of the time....which is considerably lower than the signal levels
for statistics confidence levels stipulated by the FCC: Analog F(50,50) and Digital F(50,90).

Note that the F(99,99) RX_dBm signal level is the extremely weak signal level reached
during an extremely deep fade event for one of the worst "locations"...and hence isn't easy
to correlate to anything one would measure with a signal level meter or spectrum analyzer.
F(99,99) is useful when you want to make sure that you almost never ever get a video glitch...

I found that TVFOOL's RX_dBm is about 19.5 dB lower than RADIO MOBILE calculated
Line-Of-Sight signals levels for F(50,50) [and a few dB more for F(50,90)] confidence levels....
and the difference increases for paths with increasing diffraction loss.
The delta between the two methods is usually called FADE MARGIN.

Note that F(99,99) confidence statistics result in "usable" RX_dBm levels
being considerably lower than the best Preamp and HDTV input sensitivity levels.
Despite these awkward "quirks", RX_dBm can still be used as a RELATIVE predictor
of performance....although LOS is scaled differently than 1Edge/2Edge signal levels.

In the spread sheet, I showed how to input the TVFOOL calculated data to derive the
Total Propagation Path Loss.
Once this is known for the current analog station, the spread sheet can then be used
to recalculate reception levels for a digital station after inputting the new ERP, et. al.

In the spread sheet, I also included links to additional information to download and
setup RADIO MOBILE if you want to pursue that (free) alternative.


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