Anti-interference filter for c-band

[satesco]

I hope you can clearly see the mobile antennas located in the vicinity of my antenna.Because of this all the reception in the C-band is almost compromised.That's why I have to look for an anti-interference filter.I found such filters at Norsat,here sau here.
Of course there are other filters from other manufacturers,but I don't know where to find what I need.That is why I hope that they will be enthusiasts on this forum that have had such problems and that,who knows,may have found the right solution?
I would be very grateful to the one who can recommend a suitable filter to attenuate as much as possible the massive interference from the mobile antennas seen in the picture. If you use such a filter I want to know what experiences you have and/or if it helped you?
Any suggestion or advice is welcome.Thanks.

 

[Channel Hopper]

If you can work out where the interference gets into the system (and at what frequencies) you can take steps to reduce it with filtering, but is is not guaranteed.
Good quality shielded cable, plus the removal of similar polarised cable runs (less vertical or horizontal depending on what is being transmitted by the mobile antennas) can help as well.
There is microwave protective fencing that can be used to shield the dish and can be built on a budget, it was popular in areas in the Middle east where I was posted - a few years back - as a cheap block to military / 'axis' country jamming, though the final fix near the borders was almost always excavation of earth/sand and installing the dish in a shallow pit.

 

[scopus]

I hope you can clearly see the mobile antennas located in the vicinity of my antenna.Because of this all the reception in the C-band is almost compromised.That's why I have to look for an anti-interference filter.I found such filters at Norsat,here sau here.
Of course there are other filters from other manufacturers,but I don't know where to find what I need.That is why I hope that they will be enthusiasts on this forum that have had such problems and that,who knows,may have found the right solution?
I would be very grateful to the one who can recommend a suitable filter to attenuate as much as possible the massive interference from the mobile antennas seen in the picture. If you use such a filter I want to know what experiences you have and/or if it helped you?
Any suggestion or advice is welcome.Thanks.

Titanium CBand LNB's now include a filter for this type of interference, how effective it is I have no idea..

 

[satesco]

Thank you @Channel Hopper for your intervention and suggestions
Some years ago the interference was between 3500-3700 MHz.Unfortunately,they reached the last year at 3800 MHz,with the spread of 4G.What I notice on the spectrum, and because of that many frequencies are not detected, or the signal is very much attenuated.And to minimize the interference on the cable route,I use an external coaxial cable RG11 Triset-11 used for professional installations.The interference occurred with increasing the number of mobile cells near my antenna!
Your suggestion would be good if I knew what that microwave protection fence looked like. If you have a picture of that fence, please post it so I can get an idea of what it looks like.

@scopus,
You know,I used that Titanium,but unfortunately,it didn't really help.That's why I thought about resorting to an external filter,in the idea that I could manage to reduce the interference as much as possible.
Of all the lnbs I've used, the one who helped me the most is an Taiwanese LNB,from the '90s, which has a filter on the housing. That's why it's a lot harder than LNBs in recent years.In those years, there were no economics on materials used for many electronic things.Everything was sturdy built.
Here's how this lnb looks and spectrum with interference
Best regards

 

[s-band]

As CH says, the first thing to do is to find out the frequencies of the interferers. If you have a spectrum analyser it's easy. Try to get one if possible (a general purpose one, not a satellite meter type). If not, a SDR like the AD-Pluto will cover up to 6GHz after a tweak. You might be able to use an LNB off the dish and do a normal scan but if the signals are strong the results will be confusing.

If the interference is co-channel then a filter will not do anything. Your only hope, without complex electronics, is shielding as mentioned. If it's not too strong, even a small mesh chicken wire fence may help.

If the interference is out of your band it may be causing trouble by blocking (overloading the RX which will suppress the wanted signal) that will affect most or all of the band at once. A filter to remove the blocking signal(s) may fix it. Blocking caused by radar altimeters (4.2-4.3GHz) is easy to spot with an analyser or SDR on the IF as the wanted signal will be modulated (chopped) by the radar. Blocking caused by comms links may be continuous. Do you lose the whole band at once?

If it is out of band and causing intermodulation products (2 or more signals out of band mix to produce one or more in band) it will only affect some frequencies and may also be fixed by filtering.

The above assumes it is caused by C band interference. If it is at the IF the co-ax shielding improvement may help. To find out if this is a problem, disconnect the LNB at the dish and do a full IF scan.

I'm not sure if the filtered Titanium has an extra filter but it may just have a version of the pre-mixer filter found in standard one and cut off below 3.7GHz. If that's the case, the filter might help mild cases but that's unlikely if you are line of sight to the source. If your interference is out of band, one of the waveguide filters is the best option.

Try this search string: wll - Google Search interference c band <link fixed>

<Edit> Written before your last post, additional comments:
Looking at the plots, it appears to be in-band interference so the shielding may be your only option. If you have lost SNR on other signals, there may also be blocking or intermodulation,
Shielding: Interference into satellite dish: reduction by using site shielding

 

[beavs2112]

don't forget the plots of his crazyscan are of the I.F. frequencies after being down-converted and mixed with the LO. by his LNBF then measured by his receiver (whatever card he used to generate them). Also the Norsat filters won't directly bolt onto his LNBF. they are designed to be used with a different type feedhorn. So to use them you have to buy a new feedhorn and two c-band lnb's then bolt the filters between the feedhorn and lnb.
Have any Romanian (based on satesco's given location) or other European for that matter----- wireless mobilephone operators obtained licences to operate in the 3.4 to 3.7GHZ range yet? Here in North America things are still in the planning stages. Nothing has been deployed in a large scale way in the field across the countries yet.

 

[Channel Hopper]

Thank you @Channel Hopper for your intervention and suggestions
Some years ago the interference was between 3500-3700 MHz.Unfortunately,they reached the last year at 3800 MHz,with the spread of 4G.What I notice on the spectrum, and because of that many frequencies are not detected, or the signal is very much attenuated.And to minimize the interference on the cable route,I use an external coaxial cable RG11 Triset-11 used for professional installations.The interference occurred with increasing the number of mobile cells near my antenna!
Your suggestion would be good if I knew what that microwave protection fence looked like. If you have a picture of that fence, please post it so I can get an idea of what it looks like.

I don't have images, when I was working in the Middle East the images I sent back of the projects became the property of the parent company.

The fencing I saw consisted of thin galvanised steel rods, about 8mm in diameter and spaced about 3cm apart, with supporting horizontal bars every 20cms or so. I estimate the height to be 2.5m

The reflective frequency would be based on the minimum wavelength that could pass through the gaps, I doubt the dimensions above would stop unwanted 5GHz radiation completely, perhaps nearer 3GHz but I would have to get the calculator out to verify, though looking at the reflector material on a C band only mesh dish, the gaps are no further apart than 1cm.

The following link gives dimensions of a 4-8 GHz yagi antenna, where the spacing is confirmed for minimum frequency resonance as being around the same distance.

https://edlib.net/2015/icssccet/ICSSCCET2015027.pdf

 

[satesco]

don't forget the plots of his crazyscan are of the I.F. frequencies after being down-converted and mixed with the LO. by his LNBF then measured by his receiver (whatever card he used to generate them). Also the Norsat filters won't directly bolt onto his LNBF. they are designed to be used with a different type feedhorn. So to use them you have to buy a new feedhorn and two c-band lnb's then bolt the filters between the feedhorn and lnb.
Have any Romanian (based on satesco's given location) or other European for that matter----- wireless mobilephone operators obtained licences to operate in the 3.4 to 3.7GHZ range yet? Here in North America things are still in the planning stages. Nothing has been deployed in a large scale way in the field across the countries yet.

It's good that you got my attention what I have to do from a mechanic point of view if I were to use a filter from Norsat.Thank you for that.And I will keep in mind your technical indication if I buy a Norsat filter. But before that I'm not clear if such a filter from Norsat could at least alleviate the interference as much as possible, if it can't completely eliminate them taking into account that my antenna is right next to those mobile antennas?
I have to admit that I can not precisely determine the nature of these interference so long as I do not have a special device that measures which frequencies inter-modulate with others from other sources?!That's why I do not even know if the filters I'm looking for could cover the frequencies affected by interference.But definitely the 3500-3700 MHz band, and more recently up to 3800 MHz, is influenced either from mobile or from other sources.And I realize how hard it is to give the right advice in the situation where I am while I haven't done those measurements in my area.The only app through which I can at much to figure out of these interference is Crazyscan.But of course the source of these can not find out with this utility.
Anyway,thank you for clarification.
Regards

 

[s-band]

@satesco Try this:
Remove your LNB from the dish and connect to a Crazyscan set-up.
Point the LNB at the source of the problem
Scan as wide a band as you can (~3000-4900 with a TBS69x3) - record it. Physically rotate the LNB to get the best signal. Zoom in on interference and do another scan.
If the signals are much stronger than your normal strongest C band sigs, add an attenuator to the input of the LNB (a thin damp cloth to start with?)
Scan again.
As long as the signals are not overloading the LNB or back end, it should tell the truth about he frequencies of your interference.
If you are close and can reduce the signal enough, set CS to scan just the interference and try to direction find the actual source.

 

[Terryl]

If that's your dish in that photo then good luck trying to filter out a signal that has it's source that close to the LNB.

And most commercial grade in-line LNB wave guide filters like in the links you posted, will not work on most consumer grade LNB's, they will not bolt onto the primary wave guide, you would need a commercial grade LNB for that.

And a filter in-line with the LNB output (it's IF output) will not work, as the signals need to be filtered out before they get to the internal mixer inside the LNB.

To get the job done right you would need a commercial grade setup, (C-band LNBF with a wave-guide and detachable down converter) this would be very expensive.

However if you own the property you could put up a Faraday shield, this consists of some 2x2's for a frame, with some aluminum window screen on both sides.

You would build the frame as close to the dish as possible, then the window screen is attached to both sides, the two screens are kept isolated from each other except for one ground point, this ground point is then connected to an 8 foot Earth ground rod, this ground must be seperated from the dish's ground point.

The frame needs to be big enough to totally shield the dish from the interfering signal source.

 

[beavs2112]

redundant info deleted.

 

[Terryl]

I have also seen it done with metal roofing, it must be a double sided setup, with both sides isolated except for one point.

You can use 2x4's for the frame and standard metal roofing panels.
This is not as effective as the window screen as the steel roofing panels are not as conductive as the aluminum screen..

In some applications that needed a Faraday shield, beryllium/bronze screening was used, this was a better shielding material then other metal screening material, except for use inside, then we used Mu-metal screen, but this is very expensive stuff.

 

[satesco]

Excellent technical advice,@s-band I hope the weather gets warmer so I can run tests the way you recommend.
But in the environment where my antenna is located, the sources come from several directions,some kind of web of signals,I find it hard to know which source is more important than another?
The most difficult part is that I do not know which is the strongest signal under 3700 MHz,because the signal below this frequency was weak every time although the LNB detected it but could not lock it only by accident.

Hi @Terryl,While I was answering @s-band,I see your message, which I have to study.For now, I'd like to know what an upgrade looks like to my LNB system?Please give me a link to such setup?Thanks for that

 

[Channel Hopper]

Excellent technical advice,@s-band I hope the weather gets warmer so I can run tests the way you recommend.
But in the environment where my antenna is located, the sources come from several directions,some kind of web of signals,I find it hard to know which source is more important than another?

You could try cutting wires that connect to the roof where the mobile antennas are, one by one, and see which signal disappears from the readout.

 

[Terryl]

Hummm, well you would need a commercial grade feed horn, a Norsat BPF-C-1, 2 or 3 filter and a commercial grade LNB down converter.

For this google would be the best start.

A start in looking for a feed horn would be here, Seavey ESA-40 C-Band Single Port Linear Polarity Feedhorn (4 GHz) , then look at the Norsat site for the filter and their LNB.

As you can see they all bolt together, but with those antennas that close to the dish, it may be a big waist of some serious cash to try and fix it at the LNB.

Also with a commercial grade LNB the output is not an "F" connector but an "N" type for the output to the receiver, and the coax used is not the standard RG-6 type, but 75 ohm commercial grade coax.

 

[Fisty McB]

Have any Romanian (based on satesco's given location) or other European for that matter----- wireless mobilephone operators obtained licences to operate in the 3.4 to 3.7GHZ range yet? Here in North America things are still in the planning stages. Nothing has been deployed in a large scale way in the field across the countries yet.

In the UK all the four Mobile Network Operators hold spectrum licences in this frequency block, they were obtained in an auction last year - the intention is to have these frequencies ready to use for rolling out 5G networks in the near future. There are also blocks in this band used by UK Broadband (now owned by Three) which is being used for both portable and fixed access LTE based broadband in London and Swindon under the "Relish" brand. In Ireland blocks in the same frequency spectrum are being used for fixed wireless broadband services, one of the most popular services being "Imagine".

As far as I know many countries in mainland Europe have something similar in place with varying levels of coverage. In general using the 3.4 to 3.8GHz band for terrestrial use in Europe is less problematic right now due to C Band satellite being used very little for feeds, network distribution & and DTH services in comparison to the rest of the world - the big exception being Russia who still extensively use C Band for domestic distribution. For everything else Ku Band dominates, with a small amount of activity on Ka. BUD's never really caught on over here. Of course, for those in Europe wanting to receive C Band satellite signals this isn't of much help.

 

[Terryl]

Over here in the US almost all of the small market CATV company's use "C" band for the prime programming channels and feeds, like HBO and Showtime and others, interference on these feeds from 125W, 127W and 131W would not be tolerated, the FCC would get some very angry letters and complaints.

 

[satesco]

...

As far as I know many countries in mainland Europe have something similar in place with varying levels of coverage. In general using the 3.4 to 3.8GHz band for terrestrial use in Europe is less problematic right now due to C Band satellite being used very little for feeds, network distribution & and DTH services in comparison to the rest of the world - the big exception being Russia who still extensively use C Band for domestic distribution. For everything else Ku Band dominates, with a small amount of activity on Ka. BUD's never really caught on over here. Of course, for those in Europe wanting to receive C Band satellite signals this isn't of much help.

I took the liberty of emphasising your text without your consent,because I'm agreeing to it.Unfortunately I could say,and I hope I am not mistaken,that I am one of the victims of this use by the mobile operators of the C-band.And that's because Europe does not have a similar regulation as in the USA. At least there,even if the satellite operators disagree,at least you know what you can expect.
And as they say, what is not used,is a good for all

 

[s-band]

@satesco If the problem is in-band and only interfering with things on actual frequencies of the interference, a filter will remove both wanted signals and interference. If the interference is so strong that it affects other frequencies through blocking or intermodulation products, then a filter might help. Even if you use a filter, it won't have a brick wall edge to its response so there will not be a sharp cut off at the specified frequency. Unfortunately it may be that only a big hole with a fence around has a chance, assuming your dish can still 'see' the sky! Good luck.

 

[Terryl]

If you look at the speck's for the BPF-C filters from Norsat they have good attenuation around 60 dB starting at 3.6 GHz for the BPF-C-1, even more for the BPF-C-2 that runs down to 80 dB at 3.5 GHz, as they are band pass filters, the insertion loss at the band pass is only .5 dB.

Not too bad but it would cost a bit.