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Old 21-Sep-2016, 1:42 PM   #21
jrgagne99
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Quote:
Originally Posted by rabbit73 View Post
The WCAX signal passes over two ridges, which causes scattering, resulting a non-uniform field as you saw on the hdtvprimer page. Point A is further out; point B is just before your antenna.

Actually, it looks like the signal might be diffracted by three ridges (3-edge diffraction?) on its way to my house. The first one is at 37 miles from the transmitter, then #2 at 55 miles, then #3 at 68 miles. I think my house is actually at point "B" in your zoomed in plot. So the last diffraction ridge is located about 2.5 miles away. This is consistent with my observations of the surrounding terrain. In an case, I will try to aim the antenna upward for a few days before (or maybe in parallel with) hunting around for other hot spots.

Last edited by jrgagne99; 21-Sep-2016 at 1:45 PM.
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Old 21-Sep-2016, 2:33 PM   #22
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Quote:
Actually, it looks like the signal might be diffracted by three ridges (3-edge diffraction?) on its way to my house.
TVFOOL uses the term 2Edge for 2 or more.

Quote:
I think my house is actually at point "B" in your zoomed in plot.
I don't agree:



I will not post the coordinates for your antenna without your permission.

Try it for yourself here:
http://www.heywhatsthat.com/profiler.html

enter transmitter coordinates and click on Find:


click on 3983 ft and add transmitter antenna height AGL of +151 feet in pop up window and click OK. Height AGL is found here:
http://www.rabbitears.info/tvq.php?r...ms&facid=46728



enter your coordinates, click Find, and add your antenna height

Attached Images
File Type: jpg jrgagne99p2WCAXlast6nl.JPG (92.0 KB, 615 views)
File Type: jpg jrgagne99p2WCAXsnip1.JPG (27.7 KB, 615 views)
File Type: jpg jrgagne99p2WCAXsnip2.JPG (30.1 KB, 625 views)
File Type: jpg jrgagne99p2WCAXsnip3.JPG (64.2 KB, 592 views)
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Last edited by rabbit73; 21-Sep-2016 at 4:02 PM.
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Old 21-Sep-2016, 4:01 PM   #23
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Most respectfully, I think the topographic data in this case is flawed or there is at least a difference of interpretation. Having walked through those woods to the north-west of my house, the ground is all very flat, with maybe a five-to-ten foot change in elevation at most through there. The tree-tops however are about 50-feet tall, and I think that is what the google-earth data are showing at point "B".

In fact, the Google 3D-view shows evidence of this. There is a small clearing in the middle of the woods 1/4 mile away along the signal-path that shows as a depression in Google-3D. That is definitely not the case.

See the attached picture:
Attached Images
File Type: jpg falseElevation2.JPG (142.5 KB, 77 views)

Last edited by jrgagne99; 21-Sep-2016 at 4:29 PM. Reason: north-west, not north-east
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Old 21-Sep-2016, 4:27 PM   #24
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What you say is certainly possible. Elevation used to be measured on the ground using bench marks. It is now often done by aerial survey which probably includes tree height. In any event, the ground clutter is messing with the signal.
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Old 21-Sep-2016, 4:37 PM   #25
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Quote:
Originally Posted by rabbit73 View Post
In any event, the ground clutter is messing with the signal.
Agreed.

I will try aiming the antenna up a bit, walking the roof, and then possibly stacking antennas.
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Old 21-Sep-2016, 4:51 PM   #26
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The Longley-Rice plots from www.rabbitears.info indicate about a 100-foot shift in the reception morphology for WCAX, relative to WPTZ. The shift puts my house right on the edge of a WCAX deadzone. I'm guessing this is a frequency effect, (473 MHz vs. 521 MHz) since the general reception pattern in the vicinity of my house is quite similar between each signal.
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File Type: jpg deadZoneShift.JPG (45.9 KB, 107 views)
File Type: jpg deadZoneShift2.JPG (76.6 KB, 76 views)
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Old 21-Sep-2016, 5:28 PM   #27
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Originally Posted by jrgagne99 View Post
The Longley-Rice plots from www.rabbitears.info indicate about a 100-foot shift in the reception morphology for WCAX, relative to WPTZ. The shift puts my house right on the edge of a WCAX deadzone.
You're assuming precision in the underlying input data that does not exist. The rabbitears.info calculations uses a much coarser elevation data set than does TVFool's input data, consequently, comparing the two results is not a heads-up comparison. It's somewhat akin to making a comparison in the video quality between a 1280P input source vs a VGA-resolution source on a UHD display and expecting 4K results.


Quote:
I'm guessing this is a frequency effect, (473 MHz vs. 521 MHz) since the general reception pattern in the vicinity of my house is quite similar between each signal.
Absolutely.
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Last edited by ADTech; 21-Sep-2016 at 7:52 PM.
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Old 21-Sep-2016, 7:10 PM   #28
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Quote:
You're assuming precision in the underlying input data that does not exist.
Correct

The computer simulations for the tvfool report, the Longley-Rice coverage map, and the terrain profile, give the impression of accuracy that exceeds reality. Look how I was fooled by the elevation profile.

I don't expect anything better than a location specified to an accuracy of a football field length or two.
Quote:
The Longley-Rice plots from www.rabbitears.info indicate about a 100-foot shift in the reception morphology for WCAX, relative to WPTZ. The shift puts my house right on the edge of a WCAX deadzone.
Nicely done comparison, but the tuner makes the final decision.

Your tuner will take all factors into consideration that affect signal strength and signal quality (as defined by SNR and uncorrected errors), and tell you if the signal is good enough.

When I aim an antenna, I go for max signal strength, then readjust for max signal quality. They are not always at the same azimuth because of multipath reflections.
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Last edited by rabbit73; 21-Sep-2016 at 10:53 PM.
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Old 22-Sep-2016, 1:19 AM   #29
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Originally Posted by rabbit73 View Post
Your tuner will take all factors into consideration that affect signal strength and signal quality (as defined by SNR and uncorrected errors), and tell you if the signal is good enough.
I agree completely- the TV receiver is the ultimate arbiter.

That being said, can you guys recommend a TV brand or maybe even a particular model that has additional signal quality measurements other than just signal-strength? Both of my current TV's only have a signal strength meter. Since I'd like to get a third TV for the basement anyway, I might as well get one that has additional signal diagnostics (SNR, uncorrected errors, etc.) to assist in my current effort. Generally, those kind of capabilities seem hard to find on TV spec-sheets; and blue-shirts generally don't know much about the OTA capabilities of the TVs they sell.

Also, is there a particular brand or model that is thought to have higher-quality OTA receivers than competitors?
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Old 22-Sep-2016, 3:05 AM   #30
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I have been very happy with my Sony KDL22L5000 and KDL32R400A.

KDL22L5000
Bad signal with picture freeze, SNR below 15 dB, and uncorrected errors:



Good Signal



KDL22L5000 calibration chart



My KDL32R400A has an even greater range of readings; the screen is similar. Here is its calibration chart:



So, when I bought the 32R400A, I was getting a TV and a signal level meter for the price of a TV.

KDL32R400A screen with TV connected to cable; readings are similar to OTA readings:



One of thee days I'll connect an antenna to the 32R400A and do another screen shot.

You will want to make sure the model you choose has a Diagnostics Screen. For my 32R400A:
Menu > Settings > Setup > Product Support > Signal Diagnostics

I think the smallest model now is 40". They do make a few 32", but most are Multi-System which doesn't have a tuner for ATSC.
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Last edited by rabbit73; 22-Sep-2016 at 3:45 AM.
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Old 23-Sep-2016, 2:47 PM   #31
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Originally Posted by Tigerbangs View Post
HBX-91s are cheap enough to be worth giving it a try.... combine them using a high-quality coax splitter-joiner.
HDB91X are now on sale for $39.99, so I think I'll give this a try.

Which splitter/joiner should I select? I only seem to find ones with 3.5 dB insertion loss. Wouldn't that result in a net loss?
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Old 23-Sep-2016, 5:20 PM   #32
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Don't FOR GET THE amp channel master 78/7777,or the newest one by channel master
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Old 23-Sep-2016, 6:29 PM   #33
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Which splitter/joiner should I select? I only seem to find ones with 3.5 dB insertion loss. Wouldn't that result in a net loss?
That's as good as it gets for using a splitter as a combiner.

However, when used as a combiner and everything is phased properly, that combiner loss disappears as if by magic (it's actually math**) leaving only the loss caused by power dissipation and inefficiency, typically somewhere from 0.4 up to a dB or so. Using a 1/2 dB as a planning factor is usually good enough.

** See http://www.hdtvprimer.com/ANTENNAS/ganging.html for a tutorial.
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Last edited by ADTech; 24-Sep-2016 at 2:22 PM.
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Old 14-Nov-2016, 1:52 PM   #34
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Ballasted roof mount?

Does anybody have experience with ballasted antenna mounts? I found an old Dish Network ballasted roofmount for free on the side of the road. I'm wondering I could use it to mount my 2x HDB91X's + a VHF, as opposed to buying a tripod that screws into the roof. The roof is about a 3/12 pitch and the ballast mount has room for 8 cinder blocks. Obviously, the wind loads are my main concern. My house is situated in a relatively windy area, especially in winter.
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Old 14-Nov-2016, 3:59 PM   #35
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I've used non-penetrating mounts several times. Usually a couple of cinder blocks or sand bags is all it takes but it's going to depend a lot on the footprint of your "found" mount, the mast length involved, the relative wind load of the antenna, and your roof's particulars (slope, composition, etc).
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Old 14-Nov-2016, 6:21 PM   #36
jrgagne99
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Antennas: two HDB91X's + Stellar Labs 30-2476 VHF
Mast height is 6-feet
3/12 pitch,
Asphault shingles
Mount base area= 36"x36" (Holds 8 cinder blocks 33 lbs each = 264 lbs)


My gut check says that 264 lbs is a lot, so that this ought to work...
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Old 15-Nov-2016, 4:00 AM   #37
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You may need more capture area on UHF and no yagi design will give you that and their gain tends to be on higher channels which you don't need
An 8 bay bowtie design may give you what you seek
And the channel master hd4228 is the best UHF antenna on the market as a direct result of massive capture area
If the 4228 won't pick it up then nothing will

Last edited by WIRELESS ENGINEER; 15-Nov-2016 at 4:07 AM.
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Old 15-Nov-2016, 4:00 PM   #38
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The 4228 is probably the next thing I'll try if the 2x HDB91X's don't work, plus with walking the roof to hopefully find a better spot.
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Old 19-Nov-2016, 1:46 PM   #39
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I tried combining two HDB91Xs together, and the performance did not really improve, infact, it gets a little worse. Questions on this:

1) How close to "exactly the same length" do the feed lines need to be. I'm using two 3-foot lenghts, and they vary by about 1/4". Is this too much?

2) Will it be worth fiddling with the separation? I tried 39" as a first cut, per Tigerbangs suggestion.

3) I'm guessing the antennas also need to be "perfectly parallel". Its kind of hard to ensure this exactly unless I add another cross-piece. Seems like this might be worthwhile. Thoughts?

Thanks guys!
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Old 30-Nov-2016, 9:46 PM   #40
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Bump

Bump .
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