Reception Help in NH
 

Please help!

I am trying to pull in the 5 major stations (NBC, CBS, ABC, PBS, FOX) all transmitting from a distance of 70 miles, 342-deg, 2-edge. The stations are WPTZ, WCAX, WVNY, WETK, and WFFF. Here is my report:

http://www.tvfool.com/?option=com_wr...e2cb9bbcbb2eeb

Eventually, I would like to feed 3 TVs. Over the last 8 months or so, I have been experimenting with four antennas, all with fairly similar results in one key aspect, specifically, the inability to reliably receive WCAX. The antennas are (Denny's HD Stacker, CM-5020, HDB91X, and a homemade 8-foot K7MEM yagi designed for UHF ch-22).

In general, in 5-foot AGL tests with the TV very close to the antenna (4-feet of RG-6, no pre-amp) and the antenna pointed to 342-deg, I can get WPTZ fairly reliably, with spotty pick-up of WCAX. By "spotty", I mean if I move the antenna 5-feet to the right or left it can make the difference between 40% signal for WCAX and nothing. Oddly enough, in some locations I can receive WCAX at 5ft-AGL, but when I raise the antenna tripod up to 8ft-AGL, reception dies, until I move to the right or left about 6 feet. I have confirmed that this is a spatial anomaly somewhat repeatable from day to day, not a temporal one. Very strange behavior, but I figured it would go away when I permanently mounted the antenna on the roof at 30ft.

Not so. I moved the antenna to a gable-end mount at 30-ft AGL, with a CM-7778 pre-amp and 35-feet of RG-6 and an earth-ground-block for the coax-shield now part of the setup. I figured that WCAX should come in reliably, and I would have a decent shot at the rest of the channels on my list. Well, I am able to get WPTZ, WVNY (Hi-VHF, so only receives via HD Stacker and CM-5020), and WETK reliably, and even occasionally WFFF (especially with the HDB91X). But regardless of antenna, I cannot seem to get WCAX reliably, even though it has a relatively easy NM=8.2 dB, compared to the other UHF stations that I am receiving that are lower down on the list WETK (NM=-2.2) and WFFF (NM=-5.8).

WCAX is a priority for me since it is CBS affiliate and it carries the local NFL team. Why am I not receiving WCAX? I have a few ideas, such as (1) my down-lead comes in right underneath my electrical meter, and (2) a transformer is about 100-feet away from the antenna at about 325 degrees. Could either of these be causing interference? Any offending trees are at least 300 feet away, and about 50-feet tall. If this is a multi-path "null", would an antenna with a wider capture area (e.g. DB8e) improve reception of WCAX? I suppose I could try mounting the antenna somewhere else on the roof (either on the garage gable ends, or on the middle of the roof ridgeline using a tripod) but the wife thinks it is least-offensive on the gable end of the house, since it is "balanced" by the chimney on the other end of the house. I prefer not to mount it to the garage roof, since doing so would impede reception of some other lower-priority channels to the southeast.


Thanks in advance for any help you can offer!

Good day J99 I SEE that you have a high and low VHF TV ANTENNA and a ROTOR does the ROTOR STILL work if so I would keep the VHF ANTENNA THAT you have and add a ANTENNAS DETECT 91XG at the bottom of the VHF ANTENNA 3Ft apart from eachother with a channel master 7777amp and how long has the VHF ANTENNA Ben on the HOUSE

Yes, the rotor still works. All four antennas I've been experimenting with are relatively new (<1 yr). As is the CM-7778. I have also tried a CM-7777 but that did not seem to make any difference.

For what it's worth, the signals of interest are located to the left in the whole-house photograph, so the trees at the right edge of that picture are not in my way. The intent of that picture was simply to show the current gable-end antenna location, the available roof-lines, and the telephone pole with the transformer at the top which is about 100-ft away. I have tried all four antennas at that roof-top location shown in that picture, with no real success on WCAX, yet decent signal on WETK and even WFFF, which have a noise margin over 8 dB down from WCAX.

So how high are you putting the antenna I suggest 10Ft off of the roofs line the higher the antennas the better they work and put the antennas A G L at 10 and see what happens

Welcome to the forum, JR:

Interesting question. You should be receiving it, but you are not. I don't have an immediate solution, but I will give you my thoughts, for what they are worth.:)

WCAX IS listed on the tvfool report, but there is a shortage of people on the tvfool site to keep the data base current. It is listed as on the air at rabbitears.info:
http://www.rabbitears.info/market.ph...&callsign=wcax

but when I do a zip code search it isn't listed on rabbitears.info. However, the translator for WCAX, W20CS, IS listed, but it is too weak for your area:
http://www.rabbitears.info/search.ph...pe=dBm&height=

Wiki makes me think it is still on the air:
https://en.wikipedia.org/wiki/WCAX-TV

Why don't you call the station engineer; they might be having transmitter trouble.

more later when I have time

Thanks for your reply Rabbit!

I'm pretty sure WCAX is still broadcasting, as I am able to receive "spotty" reception at ground level. I have even occasionally received it on my roof-top mount, but only marginal reception, and under the absolute best conditions, such as when early-morning fog fills in all the valleys between me and the tower located 70-miles away. In such cases, even WFFF (-6 dB NM) is coming in nice and strong. It is curious that it is one of the only signals on my TVfool report that does not have a birds-eye-view signal strength plot available for it.

I'm afraid that I am going to need to haul a TV up on the roof and check for hot spots in situ.

Is it possible you are receiving the WCAX translator, W20CS? It has the same virtual channel number. Do any of your TVs give the real channel number or frequency of a received channel in the menu?

http://forum.tvfool.com/attachment.p...1&d=1474412225

Yeah, I noticed that the coverage map was not available from the tvfool Interactive Map Browser. That made me wonder if it was really on the air. I did find a Longley-Rice coverage map on the FCC contour map:
http://www.rabbitears.info/contour.p...2.816111111111

Red is weak, no color is weaker. You can see the coverage in your area is very spotty because of the rough terrain. A small change in location can make big difference in signal strength.

http://forum.tvfool.com/attachment.p...1&d=1474412942

I have noticed the same thing at my location. The wave front presented to the antenna has a non-uniform field.

I was having trouble receiving CH 42 because my antenna was facing the wrong direction. I went across the street and setup a 2-bay UHF antenna, my meter, and a preamp. I was able to get a nice scan and a stronger signal with the antenna aimed at the transmitter for CH42.

Interestingly, when I moved the antenna a few feet left or right, without changing the height or azimuth, there was a big difference in the signal strength and scan quality. This is most likely because of the tree line in front of the antenna about 200 ft away which created the non-uniform field.

http://forum.tvfool.com/attachment.p...9&d=1442620525

I understand the need to mount the antenna in a location that "looks nice," but the antenna must be mounted where the signal is strongest, which is often not where you want it. Antenna installers call it walking-the-roof, signal level meter and test antenna in hand, to find a hot spot.

There are several possible things going on with the height. When the antenna is close to the ground, it can receive a reflection of the signal from the ground which is added to the direct signal in phase; called "ground bounce." When you raised the antenna, you lost the reinforcement from the reflection and your antenna was then behind the electrostatic field that surrounds the power line from the pole to the house.

Maybe not.
http://www.hdtvprimer.com/antennas/siting.html

scroll down to Non-uniform fields

Now that's cool LOL

I'm pretty sure it is not W20CS. With my TV in "manual" mode, when I type in "22" it automagically goes to 3.1. If I type in "20", it stays put and says "no signal". Unfortunately, the other TV is the same type, only smaller, and all the menus are exactly the same. They are circa-2008 Sylvanias.

I ordered a 7" handheld TV for fun, and will use it to try to "walk the roof" to find a hot spot when it arrives.


Tomorrow, I will try to post a picture of what the antenna "sees", to see if the you think the power line occlusion/obfuscation may be at play.

Very Interesting! In all of my research, I had not seen that particular webpage. I will study this.

If I do "walk the roof" and happen to find a hot spot for WCAX, do you think the hot spot will stay in the same place from day-to-day, and over the seasons and years?

Good question will it rabbit 73

This is the terrain profile for WCAX from tvfool:
http://www.tvfool.com/?option=com_wr...dALLTV%26n%3d7

This is the profile using different software:

http://forum.tvfool.com/attachment.p...1&d=1474416565

http://forum.tvfool.com/attachment.p...1&d=1474416999

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. I can see the ridge at point C behind your house. Using "what if" height changes on the interactive map browser:
At 115 ft 1Edge NM 17.6 dB; the signal clears point B
At 485 ft LOS NM 41.0 dB; the signal clears point A

What bothers me is, if the terrain affects WCAX, then why doesn't it affect WPTZ?

I suggest you hunt for a good location for WCAX (somewhere on you property even if it means a mast behind the house) using the HDB91X with the front of the antenna tilted up (15 deg ?) to catch the signal coming down from the ridge. You need to get the antenna as high as you can because there is a lot of ground clutter on the hill just in front of the antenna.

Yes that's where the higth and A G L comes into play is that right

My house is actually situated right on the boundary between Orange and No Color. But the my ground tests were typically in the yard or driveway, which are in "Orange". That, coupled with the ground bounce, probably explains my spotty ground reception, yet poor roof-top reception.

The hot spot stayed stable for me. My wife wanted a battery operated TV for use during a power failure. The only place it would work indoors with analog TV was by a window.

http://i496.photobucket.com/albums/r...pshazyfqkd.jpg

When digital TV came along, an indoor antenna would not work because there was an aluminum foil vapor barrier on the insulation in the outer walls; we were living in a Faraday Cage.

The landlord said I could mount an antenna outside if it did not show from the street. I selected a hot spot inside the decorator blocks on the porch. The landlady said she wanted me to move it to the left where it wasn't as obvious. I explained to her that the antenna needed to be where the signals were the strongest, and I would build an attractive enclosure for the antenna. She said OK.

http://forum.tvfool.com/attachment.p...1&d=1474419910

http://forum.tvfool.com/attachment.p...1&d=1474419910

The 4-bay UHF antenna is about 5 ft off the ground. I added a folded dipole for VHF channel 13. The signals come through the holes in the blocks without much attenuation. The VHF signals are attenuated a little more because the size of the holes is frequency related. In other words, the holes act like a high pass filter.:)

http://forum.tvfool.com/attachment.p...1&d=1474421218

All of the Burlington-Plattsburgh stations broadcast from almost exactly the same spot on Mt. Mansfield, so the issues that you are having with WCAX are most likely an issue of signal bounce because of the specific frequency of WCAX and the mountains between the transmitters and you.

Rabbit beat me to the punch when he suggested changing the tilt of the HDX-91. I have experienced going from a no-signal to a solid signal just by tilting the front of the antenna up, sometimes by more than 15 degrees. So, before you undo all of your handiwork on the roof, try the tilt first.

By the way, WFFF (FOX) has a pretty tight transmitting pattern that puts little signal out your way, so, if you see WFFF with the tilt, you ought to see WCAX without too much of an issue.

Another thought might be to horizontally stack 2 HBX-91s, which would increase the likelihood of finding additional stray signal from WCAX. HBX-91s are cheap enough to be worth giving it a try. Mount them on a fiberglass horizontal pole approx. 39"apart. Be sure that your coax cable leadin is exactly the same length from each antenna, and combine them using a high-quality coax splitter-joiner. The front end elevation tilt recommendation is still valid.

Ha tiger what is a H D X ?

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.

TVFOOL uses the term 2Edge for 2 or more.

I don't agree:

http://forum.tvfool.com/attachment.p...1&d=1474464195

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:
http://forum.tvfool.com/attachment.p...1&d=1474467002

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

http://forum.tvfool.com/attachment.p...1&d=1474467653

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

http://forum.tvfool.com/attachment.p...1&d=1474469959

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:

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.

Agreed.

I will try aiming the antenna up a bit, walking the roof, and then possibly stacking antennas.

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.

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.


Absolutely.

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.
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.

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?

I have been very happy with my Sony KDL22L5000 and KDL32R400A.

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

http://forum.tvfool.com/attachment.p...6&d=1438807158

Good Signal

http://forum.tvfool.com/attachment.p...7&d=1438807179

KDL22L5000 calibration chart

http://i496.photobucket.com/albums/r...psmz94qqxv.jpg

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

http://i496.photobucket.com/albums/r...pstasl68zu.jpg

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:

http://i496.photobucket.com/albums/r...psqjqurwtl.jpg

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.

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?

Don't FOR GET THE amp channel master 78/7777,or the newest one by channel master

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.

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.

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).

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...

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

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.

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!

Bump
 

Bump .