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jrgagne99 19-Sep-2016 5:39 PM

Reception Help in NH
 
3 Attachment(s)
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!

Nascarken 20-Sep-2016 12:44 AM

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

jrgagne99 20-Sep-2016 1:48 AM

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.

Nascarken 20-Sep-2016 2:00 AM

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

rabbit73 20-Sep-2016 8:22 PM

Welcome to the forum, JR:

Quote:

Why am I not receiving WCAX?
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

jrgagne99 20-Sep-2016 9:07 PM

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.

rabbit73 20-Sep-2016 10:58 PM

1 Attachment(s)
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

rabbit73 20-Sep-2016 11:10 PM

1 Attachment(s)
Quote:

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.
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

rabbit73 20-Sep-2016 11:36 PM

Quote:

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.
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.

Quote:

If this is a multi-path "null", would an antenna with a wider capture area (e.g. DB8e) improve reception of WCAX?
Maybe not.
http://www.hdtvprimer.com/antennas/siting.html

scroll down to Non-uniform fields

Nascarken 20-Sep-2016 11:42 PM

Now that's cool LOL

jrgagne99 20-Sep-2016 11:54 PM

Quote:

Originally Posted by rabbit73 (Post 56378)
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?

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.

jrgagne99 21-Sep-2016 12:01 AM

Quote:

Originally Posted by rabbit73 (Post 56381)
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.

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.


Quote:

Originally Posted by rabbit73 (Post 56381)
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.

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.

jrgagne99 21-Sep-2016 12:05 AM

Quote:

Originally Posted by rabbit73 (Post 56381)
Maybe not.
http://www.hdtvprimer.com/antennas/siting.html

scroll down to Non-uniform fields


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?

Nascarken 21-Sep-2016 12:10 AM

Good question will it rabbit 73

rabbit73 21-Sep-2016 12:10 AM

2 Attachment(s)
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.

Nascarken 21-Sep-2016 12:14 AM

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

jrgagne99 21-Sep-2016 12:57 AM

Quote:

Originally Posted by rabbit73 (Post 56379)

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.

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.

rabbit73 21-Sep-2016 12:59 AM

3 Attachment(s)
Quote:

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?
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

Tigerbangs 21-Sep-2016 3:11 AM

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.

Nascarken 21-Sep-2016 9:58 AM

Ha tiger what is a H D X ?


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