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Quote:
Originally Posted by andy.s.lee /forum/post/14806627


No, because the analysis is done for signal strength "in the air". The VHF "penalty" that you're talking about is usually applied "after" this point to account for lower antenna gain, lower tuner sensitivity, and higher ambient noise at VHF. If you want to account for additional VHF signal loss for these factors, you need to subtract the appropriate values from the "starting" Noise Margin value to see what final NM you end up with at your receiver.


It is true that automatically including a frequency selective adjustment factor might provide a more "fair" comparison across all channels, but this really depends on each person's setup and link budget parameters across all channels. Diving into this next level of detail is opening up a huge can of worms which we're not ready to deal with yet.

I hate seeing WBRA-DT on equal footing with other stations in the listings even though there's so much noise on low-VHF that it literally doesn't decode more than 90% of the time, or decodes in such a broken up manner as to be unwatchable. And that's with a dedicated low-VHF antenna at the very highest point on the mast. Whereas just about any UHF antenna maxes out the meter on the local UHF signals.


I hope eventually some decision is made about this, because low-VHF in reality doesn't match up to any predictions I've seen anywhere.


- Trip
 

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Discussion Starter #282

Quote:
Originally Posted by Trip in VA /forum/post/14806880


No luck. Lists WVIR-DT as too low to receive, WSLS-DT and WSET-DT are both listed with negative numbers.

It sounds like you've got a pretty high quality RF setup. I'm guessing an AD XG91 plus a CM 7777 pre-amp. With this kind of setup it is possible to get channels that have a negative Noise Margin value. With about 13 dB of antenna gain and about 3 dB of noise figure, you should be able to pick up channels down to around -10 dB NM. The fact that the NM starts out negative just means that you need a really high gain antenna to pull it up out of the noise.


Based on your feedback, I will at least make one change... I'll modify the "red" color coding so that it reaches further down into the channel list because it does look like this level of signal capture is within range of ordinary consumer-grade equipment. Hopefully, this will appear less discouraging to the people who are willing to reach out for those weaker channels.


Out of curiosity, does WVIR come in stable through most kinds of weather? Being so close to the lower limits of reception, I would think that this channel would go away sometimes. Unless, perhaps, if the FCC information about this transmitter is wrong for some reason.


Based on what I'm seeing, I think the report is still probably accurate, but we need to get used to thinking in terms of NM and what that means. If you still believe there's something terribly wrong with the analysis, then let's try to get to the bottom of it. As of right I can't tell if there's a problem, and things look more-or-less correct on the surface.



Quote:
It claims my most powerful station is the impossible to receive reliably WBRA-DT. You'll find it attached.

It's quite likely that WBRA is truly the strongest channel at your location. Low VHF really has a big advantage when it comes to diffracting over hills or the horizon, which will be the case for you at 79 miles away. However, the appearance of poor performance may be related to the gain of your VHF antenna on channel 3. What VHF antenna do you have and what is its gain on channel 3? Many of the high-VHF only antennas can get around 8 dB of gain on channels 7-13, but might only get around -4 dB of gain on channels 2-6.



Quote:
Originally Posted by Trip in VA /forum/post/14806916


I hate seeing WBRA-DT on equal footing with other stations in the listings even though there's so much noise on low-VHF that it literally doesn't decode more than 90% of the time, or decodes in such a broken up manner as to be unwatchable. And that's with a dedicated low-VHF antenna at the very highest point on the mast. Whereas just about any UHF antenna maxes out the meter on the local UHF signals.

The problem most people have with VHF channels is usually a matter of antenna selection more than the intrinsic disadvantages of VHF compared to UHF. It is often the case that people use an antenna (even if it is labeled VHF) that has poor performance on the channel of interest. This might result in taking a 10 dB hit on a channel that could have done better with a different antenna.


A properly selected VHF antenna can achieve almost the same levels of gain that a good UHF antenna can get. However, it's true that the net achievable VHF RF path will never quite be as good as UHF, so it may be the case that a slight adjustment factor is warranted. If we do include any kind of VHF "penalty" later, I suspect the difference will not be very big (maybe around 4 dB?).


Even if we penalize WBRA in your case, it would still rank as one of the strongest channels in your area. All I can suggest for now is to double-check your antenna's gain specs on channel 3 and make sure nothing else in the setup is causing problems (e.g., diplexers, traps, amps, balun, feedline, etc.).




Thanks for all your input!


Best regards,

Andy
 

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Quote:
Originally Posted by andy.s.lee /forum/post/14807612


It sounds like you've got a pretty high quality RF setup. I'm guessing an AD XG91 plus a CM 7777 pre-amp. With this kind of setup it is possible to get channels that have a negative Noise Margin value. With about 13 dB of antenna gain and about 3 dB of noise figure, you should be able to pick up channels down to around -10 dB NM. The fact that the NM starts out negative just means that you need a really high gain antenna to pull it up out of the noise.

Winegard PR-8800 and Antennacraft Y5-2-6 with Radio Shack amp.


You're missing the point though, WSLS-DT and WSET-DT are the strongest signals I have--WSLS is from the same mountain as WDBJ/WFXR/WPXR and they're at the top of the list! WSLS and WSET can both be received with indoor antennas at 79 and 53 miles, respectively. I've received both with indoor antennas at 93 and 67 miles! These are huge signals, and your analysis used to be spot-on about them. It's even more disturbing because the other stations from the exact same location (difference of mere feet) are listed at the top of the list.

Quote:
Out of curiosity, does WVIR come in stable through most kinds of weather? Being so close to the lower limits of reception, I would think that this channel would go away sometimes. Unless, perhaps, if the FCC information about this transmitter is wrong for some reason.

It maxes out the signal meter as long as my antenna's aimed at it. It's a 1000 kW signal that can be seen just about everywhere.

Quote:
Based on what I'm seeing, I think the report is still probably accurate, but we need to get used to thinking in terms of NM and what that means. If you still believe there's something terribly wrong with the analysis, then let's try to get to the bottom of it. As of right I can't tell if there's a problem, and things look more-or-less correct on the surface.

See above.

Quote:
It's quite likely that WBRA is truly the strongest channel at your location. Low VHF really has a big advantage when it comes to diffracting over hills or the horizon, which will be the case for you at 79 miles away. However, the appearance of poor performance may be related to the gain of your VHF antenna on channel 3. What VHF antenna do you have and what is its gain on channel 3? Many of the high-VHF only antennas can get around 8 dB of gain on channels 7-13, but might only get around -4 dB of gain on channels 2-6.

It's an Antennacraft Y5-2-6, dedicated low-VHF antenna. It's the biggest antenna I could find for less than $100, because I shouldn't have to spend more than $100 to receive a single station. I looked for the big Jerrold and couldn't find anyone selling it, not that I wanted to spend that kind of money anyway.


I don't know where you live and if you have any experience with it, but low-VHF digitals are terrible everywhere. It's not an antenna issue, it's an electrical noise murders signal issue. It's literally impossible to do much more than we've already done to get the signal that is supposed to be comparable to other Poor Mountain signals, and I actually care about receiving it. I've visited homes of people with the ancient huge roof antennas with full VHF elements and they can see the other Roanoke stations just fine, but not WBRA-DT!


I hate always ranting about it, but it's a real problem and I'm not sure their boost from 2.3 kW in my direction up to 9.8 kW will do much of anything. Lightning will still kill it. E-skip will still kill it. Vacuum cleaner, blender, shredder, etc will still kill it. They have a petition to move to channel 26 "in case" the money they waste on DT-3 doesn't fix the problem, not that 26 is a good option either (note where WRLH-DT falls on the plot!).


But I'm getting way off subject.


In conclusion, something's still wrong. WSET-DT and WWCW-DT should both be a lot stronger than the Poor Mountain signals, and all the Poor Mountain signals should have comparable strength. Richmond stations that just barely decode rank higher than stations which boom in regardless of how my antenna is aimed.


EDIT: Amusingly, WSLS shows up in the correct position if I choose post-transition, though both WWCW-DT and WSET-DT still appear way down the list when in terms of real world strength the latter is my strongest signal, and the former's at low power but will likely be the strongest signal from there. Post-transition still puts stations I have never received above WVIR-DT though. And how did I go from having LOS to all the stations to suddenly being 1Edge or 2Edge?


- Trip
 

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I have been using TVfool and uptill now it had been very accurate. I just re-ran these now at 11:50 PM EDT 10-5-2008, and compaired to ones I ran about a month ago, they are way out of wack, both analog and digital.


I receive DC and Baltimore analog and some DC digital without problem. The new runs don't even show them, but yet show stations I never received even when the DX'ing good.


I have attached both old and new runs.



 

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Whatever your new model is, it is waaaay off.


TV Fool is now listing channels I wouldn't have a snowball's chance of receiving. It's also displaying channels that are marginal well about channels that are solid.


The old model was very close to my actual real world results. These new results have utterly no relation to my real world experience. It's got a channel listed at 149 mi as more receivable than many at 50-60 mi. And I live in western PA: 149 mi is DXing on an excellent tropo day.


Short version: your model is broken to the point of being unusable.
 

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Discussion Starter #286
All right. Obviously there's consensus that something is terribly wrong. I haven't figured out what it is yet, but I'm working on it. Thanks for your patience. Oddly enough, my local before and after comparisons seem about right. But I'm actively hunting for the problem as we speak.


Best regards,

Andy
 

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I suggest you check your terrain calculations. At my location (specified by coordinates), TVFool previously placed the "big four" network digital stations in the Greenville SC DMA near the top of the list, in accordance with my actual reception, and showed me as having LOS to all four of them. In the new list, two of them drop severely, and are shown not as LOS but 1edge and 2edge.


These are stations WSPA-DT, WYFF-DT, WLOS-DT and WHNS-DT on the two attached plots. There are other inconsistencies in LOS / 1edge / 2edge / Tropo, for example, WNEH-DT, WGGS-DT, WNTV-DT, WOLO-DT, WJZY-DT, WLTX-DT.

 

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Discussion Starter #288
Well, well, well... I think I may have discovered the problem after all. It turns out there was a terrain loading issue which was causing erroneous terrain profiles to be used in the calculations. Let's hope this resolves the strange results that everyone was seeing.


The problems are never where you expect them to be... I was adamant about making sure the modeling algorithms remained true to the prior software version and it turns out a bug cropped up in a completely different area.


Thanks for everyone's feedback. Please keep me posted.


Best regards,

Andy
 

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Quote:
Originally Posted by andy.s.lee /forum/post/14808209


Well, well, well... I think I may have discovered the problem after all. It turns out there was a terrain loading issue which was causing erroneous terrain profiles to be used in the calculations. Let's hope this resolves the strange results that everyone was seeing.


The problems are never where you expect them to be... I was adamant about making sure the modeling algorithms remained true to the prior software version and it turns out a bug cropped up in a completely different area.


Thanks for everyone's feedback. Please keep me posted.


Best regards,

Andy

Hey:


Looks good! My plot now looks correct again. =) I've attached it. I told you I wasn't insane.



Any chance you can add the ERP back in or at least check something for me? WSLS is now listed as LOS and as a local, but it's still low, and I'm wondering if you're using the old 55.46 kW STA or something instead of their 950 kW signal they're running now. It looks correct on the post-transition plot where they have a 1000 kW CP.


EDIT: Also, don't know if you want it, but here's my experience if you want to resharpen the red/gray cutoff. I can see WRIC/WTVR/WRLH with breakups all the time, I think if I put the UHF antenna at the top of the mast instead of the VHF, I'd see them clearly. I see signal for WHTJ but not enough to decode, and WVAW-DT isn't on the air, and would get stomped by WBRA analog if it was. No WXII but I think that's related to 950 kW worth of WSLS-DT on 30 (destroys WVIR analog too). So I can get signals down to about -3 NM with no atmospheric help. It bodes positively for post-transition performance, when WHTJ will move into the positive range. Maybe I'll be able to get PBS from there.


- Trip
 

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Discussion Starter #290

Quote:
Originally Posted by Trip in VA /forum/post/14808217


Looks good! My plot now looks correct again. =) I've attached it. I told you I wasn't insane.

That's great to hear, and your feedback is very much appreciated.



Quote:
WSLS is now listed as LOS and as a local, but it's still low, and I'm wondering if you're using the old 55.46 kW STA or something instead of their 950 kW signal they're running now. It looks correct on the post-transition plot where they have a 1000 kW CP.

The FCC data still lists the 1000 kW CP as post-transition only. There is not indicator to say that this record will take effect prior to 2/17/09. For many other stations, the FCC data correctly shows records that are valid for both pre- and post-transition. I'm not sure why this one was not recorded that way, but I'll put in a correction for it right now.




Best regards,

Andy
 

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Yeah, they have a 1000 kW CP for post-transition, but right now they're running 950 kW, which should be negligible as far as coverage is concerned.


The FCC database is, sadly, riddled with errors as the FCC tries to sort through the digital transition. I've held off on contacting them for the time being as I'm sure there's much more pressing matters, but I'll likely try and get in touch with them about it next year if they don't clear up. I'm aware of two errors in this market alone (WSLS and the other is WDRL, which is doing 43 kW from the same tower that their post-transition 63 kW signal will be using).


Glad I could help. Your site is a resource to us all, and I thank you for it!



- Trip
 

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Aaah, that's better!
My results are mostly consistent with the previous ones now. Some stations shift up or down a little, relatively speaking.


For what it's worth, with an AntennasDirect 91XG and a CM 7777 pre-amp, I get everything down to WACH-DT at NM 11.6, most of the time (including daytime), except for W65DS, a digital translator that hasn't come on the air yet.


Below that are some stations with severe local blockage from trees and buildings, or co-channel interference. Then comes WRLK-DT at NM -0.9 which I can usually receive throughout the day. Then come WCCB-DT (-8.6) and WSOC-DT (-8.9) which are usually watchable evenings/nights. Below that is "occasional tropo" territory. (Again all this excludes translators. We don't have any digital translators or LP stations active yet.)
 

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Numbers here look a lot better, too. There were a couple of distant stations showing up as fairly strong post-transition before, but now they are about where I expect them to be!


I pull in everything down to KTBC-DT (NM 2.3) very strongly with a 91XG and HDP-269 preamp. (The HDP-269 is the best I can do thanks to the booming signal of KXAM-DT nearby.) I guess that's about what one would expect here.

 

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I am now getting a more accurate result using an exact address vs. coordinates. I still think listing the stations transmitter power would be beneficial since things are changing so often now. I definitely like the new look!!


Nice job Andy!!
 

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Quote:
Originally Posted by andy.s.lee /forum/post/14806627


Could you please try again? The fixed FCC database interpretation may have something to do with this.

Thanks, Andy. At first glance, the corrected plots appear to be much more accurate (for UHF). They also appear to be much closer to reality than the old TV Fool plots for my 2 locations.


However, the Low-VHF NM results are about 10dB more optimistic than they should be. I understand your arguments for keeping it as-is (since exact local man-made noise levels are impossible to determine), but as a visual aid, I think it is important to let people know that they need to work harder for Low-VHF reception.
 

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Andy,

I really love the new TV Fool. It seems to work better than the old one, and I like the new layout. Thanks for all the work!!!


There are still some outstanding database issues.


TV Fool:

There are a few things I adressed in Post 219 I've noticed some missing virtual channel numbers and networks.


The only other additional thing is the FCC database error on WKBT-DT (their doing way more than 9KW, but I have no documented proof other than the experience of myself and other locals who pick it up easily with rabbit ears at 60 miles)


FM Fool:

K280EL (which became KLCX and moved to a different location) is still showing up, yelling "delete me!!!"
 

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Quote:
Originally Posted by andy.s.lee /forum/post/14806627


As for this station and other Class A and Low Power transmitters, the FCC has not offered much yet in terms of details for the transition.

Yes, for instance, as just one example given FCC has said(per statutory requirements i.e. - telecommunications act) LP's must be off 60-69 at end of transition period, and given they have modified the table of frequency allocations for post-transition in CFR via their Channel 60~69 reallocation order to reflect that --- I would have thought they would have by now, clarified the issue discussed earlier concerning ch 60~69 in CFR Sec. 74.402 and 74.786(current versions available at below link) :

http://www.hallikainen.com/FccRules/2008/74/702/

http://www.hallikainen.com/FccRules/2008/74/786/


But of course, it doesn't seem they have ... However, 74.786 (e) dealing with DTV "digital conversion(digital companion channels) channels on 60~69 might lead one to *assume* at least Digital LP's on 60~69 (it doesn't say anything about analog) that don't cause interference to the new services/etc. can remain there post-transition .....


Anyway, perhaps we'll see some activity from FCC soon regarding these matters -- Hopefully Including perhaps a analog shut off date for LP's ... something FCC had previously said at one point they had "planned" on possibly addressing in Third Periodic DTV review(but they didn't) ....
 

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Quote:
Originally Posted by mattdp /forum/post/14811359


Andy,

I really love the new TV Fool. It seems to work better than the old one, and I like the new layout. Thanks for all the work!!!

Agreed. The more I look at the results, the more I like the idea behind the NM calculation. I think a zero-based metric which measures signal usability -- and accounts for the differences between a "usable" analog and a "usable" digital signal -- will be a lot easier for less technical people to understand than looking at dBm. Especially now that all the results look accurate for me!
 

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Andy,

Well done!

The new set up does have a more intuitive look and feel.

The results using my address are spot on.
 
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