Terrestrial shield (1 Viewer)

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mkv7196

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Well-Known SatelliteGuys Member
Oct 17, 2015
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Calgary, AB
Anyone made a terrestrial shield for their dish? I seem to be getting some interference every now and again (shows up as packet losses in dvb card software / pixelated screen on tv). I was thinking of getting a large cardboard box and wrapping one side with aluminum foil and putting it on each side of the dish to see if there are improvements.
 

mkv7196

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Well-Known SatelliteGuys Member
Oct 17, 2015
30
1
Calgary, AB
It happens on most transponders but is less & less frequent as the dish is moved away from true south and towards satellites lower on the horizon.
 

Titanium

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Just a guess, but the interference is likely in front (south) of the dish if it goes away when on either side of the arc.

With terrestrial interference in front of the dish the surface would need to be shielded from the source with either a RF fence or moved behind a structure and shoot over the top.

I would definitely do a site survey to find the source. Might be a bad power transformer, WiFi, etc. Sometimes easier to fix the source, especially if a power company transformer or a out of band harmonic from a licensed service.
 

olliec420

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Jun 4, 2007
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I would definitely do a site survey to find the source. Might be a bad power transformer, WiFi, etc. Sometimes easier to fix the source, especially if a power company transformer or a out of band harmonic from a licensed service.

Holy crap, that can happen? Does it affect c-band so much, just because the reflector is huge? Or is the c-band freqs just commonly over lapped?
 

wvman

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Just a guess, but the interference is likely in front (south) of the dish if it goes away when on either side of the arc.

With terrestrial interference in front of the dish the surface would need to be shielded from the source with either a RF fence or moved behind a structure and shoot over the top.

I would definitely do a site survey to find the source. Might be a bad power transformer, WiFi, etc. Sometimes easier to fix the source, especially if a power company transformer or a out of band harmonic from a licensed service.

What exactly is an RF fence, and how do you build one?
 

Titanium

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Holy crap, that can happen? Does it affect c-band so much, just because the reflector is huge? Or is the c-band freqs just commonly over lapped?

Antennas collect energy. They don't discriminate between the signal that you want to receive and signals that are present in the air. An arcing power transformer is simply a broadband transmitter. Other transmitters may emit harmonics outside the primary intended frequency or may share the frequency.

In the 80's, C-band installs were plagued by telephone company towers microwaves and radar. Today we have even more potential sources of interference as almost everything around us is "connected". There are so many potential sources of interference between any of our devices.

A site survey will narrow down the what (is interfering) and where (it is coming from). Then it just becomes how (to avoid or eliminate).
 

olliec420

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Jun 4, 2007
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They don't discriminate between the signal that you want to receive and signals that are present in the air.

I got ya, but doesnt the LNB only listen for its "range" freqs? Or the neighbors 900mhz cordless is so strong, my LNB can't "hear" the c-band freqs? Just example.
 

Titanium

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What exactly is an RF fence, and how do you build one?

An RF fence (or wall) is any structure that will attenuate the problematic signals. Signals in this high frequency range are usually line of sight and can be easily blocked and absorbed. Often an existing structure may be used to block and shield the dish from unwanted signals. In the eighties, we would often use a house, barn or stand of trees to block interference from local telephone relay towers. Once we determined where the interference was coming from, we would propose to the customer where to locate or relocate the dish. If the location wasn't acceptable, we occasionally would construct a 2' cylinder on the dish edge or a 8' + wall (fence) out of chicken wire or 1/2" hardware cloth. http://www.homedepot.com/p/HDX-1-2-in-x-4-ft-x-25-ft-Hardware-Cloth-308226HD/204331883 . To support the fence (wall) we would usually use chain link fence hardware and the poles would provide a good ground for the fence material.
 
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Titanium

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I got ya, but doesnt the LNB only listen for its "range" freqs? Or the neighbors 900mhz cordless is so strong, my LNB can't "hear" the c-band freqs? Just example.

LNBs and LNBFs receive a wide block of frequencies (often beyond the specs) and downconvert to an intermediate frequency block then the tuner selects the frequency to tune. The problematic signals (noise) may be terrestrial services licensed to share the same frequency range as the satellite signal or actually be transmitted on a different frequency. Sometimes divisions and multiples of this carrier's frequency might result in a harmonic generated signal(s) (either in the transmitter or passively) that is located above and below the actual carrier. These signals (even if outside of the frequency range of the LNB) can overload the LNB and deafen it to receiving any signals. If interference is down converted and sent through the coax, it may swamp the tuner front end and make it deaf to receiving the desired signals.

Several types of filters can be used to address different types of interference. Most common is the mechanical inline filters, which are tuned during manufacturing to remove a specific narrow frequency or a broad range. They are not user adjustable and are quite expensive.

On the Titanium C1-PLL interference filter model we use a PCB trace filter on the input to remove all frequencies below 3595MHz from being passed into the down conversion circuit. This is just one method of controlling out of band interference, but it addresses the most common type of interference with wide area wireless data services.
 

olliec420

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Jun 4, 2007
751
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Pensacola, FL
LNBs and LNBFs receive a wide block of frequencies (often beyond the specs) and downconvert to an intermediate frequency block then the tuner selects the frequency to tune. The problematic signals (noise) may be terrestrial services licensed to share the same frequency range as the satellite signal or actually be transmitted on a different frequency. Sometimes divisions and multiples of this carrier's frequency might result in a harmonic generated signal(s) (either in the transmitter or passively) that is located above and below the actual carrier. These signals (even if outside of the frequency range of the LNB) can overload the LNB and deafen it to receiving any signals. If interference is down converted and sent through the coax, it may swamp the tuner front end and make it deaf to receiving the desired signals.

Several types of filters can be used to address different types of interference. Most common is the mechanical inline filters, which are tuned during manufacturing to remove a specific narrow frequency or a broad range. They are not user adjustable and are quite expensive.

On the Titanium C1-PLL interference filter model we use a PCB trace filter on the input to remove all frequencies below 3595MHz from being passed into the down conversion circuit. This is just one method of controlling out of band interference, but it addresses the most common type of interference with wide area wireless data services.

Ahhhh, I get it. This is fascinating. Thanks for the explanation that was real clear. Titanium, I hope you get paid for all this!
 
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mkv7196

Thread Starter
Well-Known SatelliteGuys Member
Oct 17, 2015
30
1
Calgary, AB
Another observation I've noticed is that there is almost no interference during the night (say 10pm-7am). Mostly happens during the daytime.
 

wvman

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Sep 19, 2014
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LNBs and LNBFs receive a wide block of frequencies (often beyond the specs) and downconvert to an intermediate frequency block then the tuner selects the frequency to tune. The problematic signals (noise) may be terrestrial services licensed to share the same frequency range as the satellite signal or actually be transmitted on a different frequency. Sometimes divisions and multiples of this carrier's frequency might result in a harmonic generated signal(s) (either in the transmitter or passively) that is located above and below the actual carrier. These signals (even if outside of the frequency range of the LNB) can overload the LNB and deafen it to receiving any signals. If interference is down converted and sent through the coax, it may swamp the tuner front end and make it deaf to receiving the desired signals.

Several types of filters can be used to address different types of interference. Most common is the mechanical inline filters, which are tuned during manufacturing to remove a specific narrow frequency or a broad range. They are not user adjustable and are quite expensive.

On the Titanium C1-PLL interference filter model we use a PCB trace filter on the input to remove all frequencies below 3595MHz from being passed into the down conversion circuit. This is just one method of controlling out of band interference, but it addresses the most common type of interference with wide area wireless data services.

Is there any plans to produce a dual output LNB with these filters integrated into them. I'd definitely be interested in a few of them. I'm getting more suspicious all the time about some sort of interference, terrestrial or otherwise as more of the channels I watch exhibits characteristics that certainly point that direction. Right now, I am investigating the possibility that my electric meter, which was upgraded about the time some of this started to happen, to see if the power company offers a solution to the problem if it's coming from line transmissions from their equipment.
 

Shicks4

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Aug 29, 2015
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Well, im not one whos trying to start a conspiracy about smart meters, I didnt even know what one was until about a year ago. But i did look then up after i discovered it might be my problem. All I can say is wow on some of the videos i have seen on you tube. So anyways Wade (the power company guy) came by last night and wanted to see what was happening on my tv. So I turned the tv over to movies! and you could literally count to 10 and like clock work the picture would blink to black and then come back. he asked what all channels did this and i explained what i found, and that the signal meter shows interference on all signals but only the weaker ones have picture quality affected. So we walked out to the meter and sure enough you could count to 10 and the meter would blink to a transmission cycle. He said he didnt think they were supposed to be transmitting every 10 seconds. Then he tells me the gas company installed smart devices too, and shows me the gas meter. I had no idea they even did that. I ask him exactly how they are supposed to work and he said they are supposed to transmit to the nearest receiver. But then he tells me that there are some of the meters in town that wont transmit in a chain or even to an office but to the beacon over in Freeport. Freeport is 26 miles away so they obviously have some power behind the transmissions. He said he would look and see how my meter was transmitting tomorrow, and might even change out my meter to see if the problem goes away. So it appears that they might try to do something with this issue for me, and I am not even sure it really is the smart meter. I told him i didnt have the equipment to check to be sure. He told me it could either me my meter or the neighbors meter, but again said that he didnt think they were supposed to transmit every 10 seconds. He said mine obviously is and would look into it. So score one for knowing a bunch of people in a small town.
 

armadillo_115

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Jun 10, 2015
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Virginia
As a temporary test, I would: Ground a piece of metal screen wire and place it near the meter and see if the interference stops.

Easier and more effective to erect a small shield near the offending meter rather than a large shield at the dish, if necessary (Hopefully the meter does not need to broadcast directly toward the dish location) That's assuming the utility company doesn't resolve the issue as the should.
 

Titanium

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Shielding the transmitter is not a great solution. Most automatic data reporting systems regulate the output RF to maintain a link within specified levels. Shielding the transmitter may actually make the situation worse as the transmitter output may be increased.
 
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olliec420

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Jun 4, 2007
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Pensacola, FL
Well, im not one whos trying to start a conspiracy about smart meters, I didnt even know what one was until about a year ago. But i did look then up after i discovered it might be my problem. All I can say is wow on some of the videos i have seen on you tube. So anyways Wade (the power company guy) came by last night and wanted to see what was happening on my tv. So I turned the tv over to movies! and you could literally count to 10 and like clock work the picture would blink to black and then come back. he asked what all channels did this and i explained what i found, and that the signal meter shows interference on all signals but only the weaker ones have picture quality affected. So we walked out to the meter and sure enough you could count to 10 and the meter would blink to a transmission cycle. He said he didnt think they were supposed to be transmitting every 10 seconds. Then he tells me the gas company installed smart devices too, and shows me the gas meter. I had no idea they even did that. I ask him exactly how they are supposed to work and he said they are supposed to transmit to the nearest receiver. But then he tells me that there are some of the meters in town that wont transmit in a chain or even to an office but to the beacon over in Freeport. Freeport is 26 miles away so they obviously have some power behind the transmissions. He said he would look and see how my meter was transmitting tomorrow, and might even change out my meter to see if the problem goes away. So it appears that they might try to do something with this issue for me, and I am not even sure it really is the smart meter. I told him i didnt have the equipment to check to be sure. He told me it could either me my meter or the neighbors meter, but again said that he didnt think they were supposed to transmit every 10 seconds. He said mine obviously is and would look into it. So score one for knowing a bunch of people in a small town.

So are the smart meters transmitting a wireless signal like a cell phone or are they transmitting over the powerlines such as BPL (broadband over powerline). I always assumed it was the latter.
 
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