5G interference questions

[OswaldFTA]

Hello

I'm confused about the new LNBFs with 5G filtering capabilities. According to the data that I found on internet:

5G signals are split on three bands, low, medium (C-band) and high. One of the medium bands, specifically the N77 band (3.7 GHZ) goes from 3.300 Mhz to 4.200 Mhz, but in the US is limited to 3.300 Mhz to 3.980 Mhz.

How is possible that the LNBFs can filter those very strong interferences (signals) that have the same frequency used by the C band satellite signals and at the same time receive the very weak signals that come from the satellite?

Will be possible that, for example, using the C138 LNBF (3.800 Mhz to 4.200 MHz) can I receive the 3.700 MHz frequencies that comes from some transponders?

Will be all those C-band frequencies used in the US moved in the near future to the range of 4.000 to 4.200 Mhz in order to have at least 20 Mhz of guard band with 5G signals?

Is there any web site to know exactly the location of the 5G towers in my area?

 

[primestar31]

Titanium

 

[N6BY]

...Will be possible that, for example, using the C138 LNBF (3.800 Mhz to 4.200 MHz) can I receive the 3.700 MHz frequencies that comes from some transponders? ...
]

No. For that reason, you should get a C138 only if you are experiencing interference (pixelation and picture breakup) on transponders above 3.8 GHz. Currently 5G band N77 usage is limited to 3.7 to 3.8 GHz.

But despite the current 3.8 GHz upper limit, 5G signals can be so strong that they interfere above 3.8 GHz. In my area 5G is strong and a C138 was necessary.

Will be all those C-band frequencies used in the US moved in the near future to the range of 4.000 to 4.200 Mhz in order to have at least 20 Mhz of guard band with 5G signals?

Next year (maybe?) band N77 will be from 3.7 to 3.98 GHz. When that happens you will need a new C-Band LNBF which filters out everything below 4 GHz..

Is there any web site to know exactly the location of the 5G towers in my area?

I haven't found one that would explain why 5G is so strong at my home. Maybe someone else here knows of one that is up to date?

Meanwhile, I am working on a 5G directional antenna to use with my software defined radio to help locate where 5G near me is coming from.

But the towers are not the only source of potential interference. 5G phones also (of course) transmit as do 5G home internet gateways.

Below is an excerpt from Verizon's Home Internet Gateway specs:

You can see that 5G band n77 is listed.

The iPhone 14 also supports the above bands plus the mm bands above 26 GHz.

 

[primestar31]

Next year (maybe?) band N77 will be from 3.7 to 3.98 GHz. When that happens you will need a new C-Band LNBF which filters out everything below 4 GHz..

IF that finally happens in my area, I'm going to take down my C-band dish and hang it up forever. I'll go back to KU only, and feed hunt.

 

[N6BY]

IF that finally happens in my area, I'm going to take down my C-band dish and hang it up forever. I'll go back to KU only, and feed hunt.

With any luck the fight between 5G cellular and aircraft owners with radar altimeters will drag on for years, and I hope that aircraft safety prevails.

 

[OswaldFTA]

No. For that reason, you should get a C138 only if you are experiencing interference (pixelation and picture breakup) on transponders above 3.8 GHz. Currently 5G band N77 usage is limited to 3.7 to 3.8 GHz.

But despite the current 3.8 GHz upper limit, 5G signals can be so strong that they interfere above 3.8 GHz. In my area 5G is strong and a C138 was necessary.


Next year (maybe?) band N77 will be from 3.7 to 3.98 GHz. When that happens you will need a new C-Band LNBF which filters out everything below 4 GHz..


I haven't found one that would explain why 5G is so strong at my home. Maybe someone else here knows of one that is up to date?

Meanwhile, I am working on a 5G directional antenna to use with my software defined radio to help locate where 5G near me is coming from.

But the towers are not the only source of potential interference. 5G phones also (of course) transmit as do 5G home internet gateways.

Below is an excerpt from Verizon's Home Internet Gateway specs:
View attachment 160119

You can see that 5G band n77 is listed.

The iPhone 14 also supports the above bands plus the mm bands above 26 GHz.

Thanks a lot for the explanation. Just to be sure of what you said. If I'm receiving a satellite signal with a frequency of 3.700 Mhz and the interference signal that comes from the 5G cellular tower has the same frequency, it will be impossible to get that satellite signal even using the most advanced LNB with all the possible filters. Is this right?

Also, I found a web site Cellular Tower and Signal Map that inform about the location and characteristics of the cellular towers. It seem that in my area the only tower that is transmitting 5G signals is using 5G low band frequency.

 

[N6BY]

Thanks a lot for the explanation. Just to be sure of what you said. If I'm receiving a satellite signal with a frequency of 3.700 Mhz and the interference signal that comes from the 5G cellular tower has the same frequency, it will be impossible to get that satellite signal even using the most advanced LNB with all the possible filters. Is this right?...

Even the most expensive 5G cavity filters don't know the difference between a 5G signal vs. a satellite signal at the same frequency. If you are currently having 5G interference your best bet right now is a Titanium C138. I have one and it works OK with my 10' dish but not with my 8.5' dish (which is on the other side of the house).

The only way to continue getting 3700-3800 would be to build an RF blocking fence around the dish and use an unfiltered LNBF. At today's prices for wire mesh it wouldn't be cheap.

 

[OswaldFTA]

Even the most expensive 5G cavity filters don't know the difference between a 5G signal vs. a satellite signal at the same frequency. If you are currently having 5G interference your best bet right now is a Titanium C138. I have one and it works OK with my 10' dish but not with my 8.5' dish (which is on the other side of the house).

The only way to continue getting 3700-3800 would be to build an RF blocking fence around the dish and use an unfiltered LNBF. At today's prices for wire mesh it wouldn't be cheap.

I understand. Would you have any information about the RF blocking fence? Material. dimensions, layout, etc...

 

[N6BY]

I understand. Would you have any information about the RF blocking fence? Material. dimensions, layout, etc...

The one I built didn't work, so I am not the best person to answer that question.

If you want to read about my failed attempt, check this thread: 5G Network interference: starting around post #23.

In summary, I used 1/16" aluminum mesh (the kind used for window screens) and wrapped it around the outside rim of my dish. I used PVC pipe to create a frame to wrap the mesh around.

Not only did it fail, but it was the ugliest thing I have ever seen!

I took it off of the dish and replaced the unfiltered LNBF with the C138. I am getting good reception (most of the time). But for some strange reason, when I do blind scans I get a random number of transponders. Sometimes it gets all the transponders and other times it misses a few.

 

[OswaldFTA]

The one I built didn't work, so I am not the best person to answer that question.

If you want to read about my failed attempt, check this thread: 5G Network interference: starting around post #23.

In summary, I used 1/16" aluminum mesh (the kind used for window screens) and wrapped it around the outside rim of my dish. I used PVC pipe to create a frame to wrap the mesh around.

Not only did it fail, but it was the ugliest thing I have ever seen!

I took it off of the dish and replaced the unfiltered LNBF with the C138. I am getting good reception (most of the time). But for some strange reason, when I do blind scans I get a random number of transponders. Sometimes it gets all the transponders and other times it misses a few.

It seems that the lack of effectivity comes with the use of a very fine mesh. I found these comments made by Titanium some time ago:

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.

 

[Comptech]

Might just be me, but I am thinking a lot of people are using 5G as a excuse for a dish that needs fine tuning. I get 5G service on my phone here full bars and I am rural, so I would guess 3.7 MHZ. I have no problem with my dish.

 

[SDA_FL_USA]

Well the pro sales folks say were going to need at least a 12 footer and a filter if around cities but rural may be ok. Have to wait and see I guess. My dish is fine tuned and not seeing any big issues from 3820-4200 but 105w 3712V 3000 is breaking up bad here thinking 5g maybe. It's a Spanish channel so no big deal anyway for me don't speak it. I am rural here also.

 

[Inclined Orbit]

The one I built didn't work, so I am not the best person to answer that question.

If you want to read about my failed attempt, check this thread: 5G Network interference: starting around post #23.

In summary, I used 1/16" aluminum mesh (the kind used for window screens) and wrapped it around the outside rim of my dish. I used PVC pipe to create a frame to wrap the mesh around.

Not only did it fail, but it was the ugliest thing I have ever seen!

I took it off of the dish and replaced the unfiltered LNBF with the C138. I am getting good reception (most of the time). But for some strange reason, when I do blind scans I get a random number of transponders. Sometimes it gets all the transponders and other times it misses a few.

Mesh screens around dishes can be very difficult to build right and in many cases will not address the problem. The commercial one's I've seen around Intelsat sites for their critical monitoring dishes were made of fine copper mesh and I had one 11m C-band dish project that required a huge shield wall around it to prevent our extended C-band transmissions from interfering with some local terrestrial stuff. That wall was taller than the dish, covered both sides and back of the dish, was about 1ft thick with perforated stainless steel corrugated sheet on both sides.

In testing this shield wall at various distances with a spectrum analyzer and horn antenna I found some uplink dish sidelobes were hitting the wall creating "creeping wave" RF currents over the inside surface of the wall then when these creeping waves hit a discontinuity like the sharp top edge and they would scatter and create an RF hot spot that would spray over the wall and that I could pick up about 40mi away on a hill top. With my background in radar cross section measurements I knew there needed to be gently curved structures that would direct the creeping waves away from the top edges of the shield wall and dissipate them in harmless directions, or the wall needed RAM (radar absorbent material) installed around the upper edges to absorb the RF rather than spray it over the wall.

I also don't believe grounding the screen or wall will have much effect as RF doesn't know to head towards ground and its primary mode is reflecting energy away. Grounding would be more of an NEC or lightning mitigation thing.

Anyway, for the backyard dish person getting blitzed by 5G C-band interference, your chances of building a shield wall or screen and having it work are slim. In my opinion, if the 5G source is line of sight to your dish and less than a couple hundred yards away, it will never work. Going from a typical back yard prime focus dish to a Cassegrain type will reduce some interference since you won't have a feed horn high in the air with all its side lobes looking out the sides at the horizon. That with a distant 5G source and a well designed shield wall and you can probably cut the interference down 30dB or more in some directions.

 

[Captain Midnight]

Might just be me, but I am thinking a lot of people are using 5G as a excuse for a dish that needs fine tuning. I get 5G service on my phone here full bars and I am rural, so I would guess 3.7 MHZ. I have no problem with my dish.

Your 5G service may just be in the 600MHz range if you are rural.

Well the pro sales folks say were going to need at least a 12 footer and a filter if around cities but rural may be ok. Have to wait and see I guess. My dish is fine tuned and not seeing any big issues from 3820-4200 but 105w 3712V 3000 is breaking up bad here thinking 5g maybe. It's a Spanish channel so no big deal anyway for me don't speak it. I am rural here also.

I am in a suburb city of 20k and still can get away with my 3.4-4.2 LNBs. I cannot lock signals in the 3.7Ghz range very often but I do receive a stable picture from a signal on 115w @3.425GHz that is from a latin uplink. Everything 3.8-4.2GHz is working well.