Lets Talk LTE Interference

Reception, channel detection, network issues, CableCARD setup, etc.
NOYB
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Joined: Thu Dec 12, 2013 2:12 am

Lets Talk LTE Interference

Post by NOYB »

I have some mixed feelings about posting this because I don't want to promote SD LTE filter sales. But there seems to be some misunderstandings about LTE interference and the use of an LTE filter. Though by well meaning people I think it tends to mislead people into thinking they don't need a filter when they do. Perhaps some discussion may improve our understandings of the situation.

Much of the chatter seems to be that close proximity to cell tower(s) is prime reason to use an LTE filter. No argument with that really. But it seems to imply that an LTE filter is of little to no use if there are no close proximity cell tower(s). Which can be misleading.

Just about everyone in civilized society has a cell phone. To communicate they have to transmit a signal of significant strength to reach the cell tower. Being that the cell phone is many orders of magnitude closer to your OTA TV antenna it has significant potential to overdrive the TV receiver. Thus interfering with the reception of the TV signals. Furthermore, the more distant the cell tower is, the stronger the signal the cell phone has to transmit in order to reach the cell tower. Making it even more likely to overdrive the TV receiver.

In addition to this, in densely populated areas there are a lot more cell phones in close proximity to your OTA TV antenna (not just yours and family). And they are in frequent use.

Another misunderstanding seems to be that if the TV signals are strong and clean. Such as close proximity to TV tower(s). Then an LTE filer is not needed. But if the TV receiver is overdriven, it matters not how strong and clean the TV signal is. It can't get through an overdriven receiver.

In conclusion it is my opinion that just about every OTA TV antenna received signal should be passed through an LTE filter before entering a TV receiver or signal amplifier. The exception would be perhaps a TV receiver that doesn't pass RF higher than channel 36. Built-in LTE filter. Perhaps this will be the case for new TV receivers and signal amplifiers at some point in the future.

gggplaya
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Re: Lets Talk LTE Interference

Post by gggplaya »

NOYB wrote: Tue Feb 16, 2021 1:54 am The exception would be perhaps a TV receiver that doesn't pass RF higher than channel 36. Built-in LTE filter. Perhaps this will be the case for new TV receivers and signal amplifiers at some point in the future.
I think a built in LTE filter in Tv's would be a bad idea. The FCC could re-auction frequencies in the future. So who knows what the frequency spectrum will look like in the future.

nickk
Silicondust
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Re: Lets Talk LTE Interference

Post by nickk »

US model HDHomeRun tuners support cable TV up to 1GHz so we can't filter out 618+MHz.

The approach in Europe is to build the LTE filter into antennas.

Nick

NOYB
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Re: Lets Talk LTE Interference

Post by NOYB »

Probably could be but would require a dynamically applied filter depending on mode/what is tuned in. Probably not worth the cost for it to be built-in. Besides many antennas are split to multiple devices/tv's and thus should have an external filter anyway.

nickk
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Re: Lets Talk LTE Interference

Post by nickk »

BTW - we created the Silicondust LPF-608M LTE filter because at the time there were no other filters with the correct pass/block range (pass 608MHz block 618MHz). Most blocked at 700MHz or 600MHz.

For example the ChannelMaster CM-3201 filter I have here is labeled "Pass 5-599 MHz Block 600-2000 MHz". Channels 35 and 36 use bandwidth above 600MHz.

NOYB
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Re: Lets Talk LTE Interference

Post by NOYB »

I posted about that in different thread several months ago. CM said the 600MHz on the label referrers to the 600MHz LTE band. Not the the filter spec. That also coincides with actual test results that have been posted in the AVS forums. Where it is down about 3.3 dB at channel 36. That is similar to the measurements a reviewer on Amazon posted of the SD filter.

According to CW's review on Amazon with measured specs.
"Ch36 (602,608MHz): -2.2, -4.7dB respectively"

nickk
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Re: Lets Talk LTE Interference

Post by nickk »

NOYB wrote: Tue Feb 16, 2021 12:39 pm CM said the 600MHz on the label referrers to the 600MHz LTE band. Not the the filter spec.
The CM one I have here is labeled "CM-3201" and "Pass 5-599 MHz Block 600-2000 MHz". It doesn't say "600MHz LTE band" or have any other references to 600MHz on the filter.

nickk
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Re: Lets Talk LTE Interference

Post by nickk »

cm-3201.jpg
cm-3201.jpg (236.69 KiB) Viewed 243 times

NOYB
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Re: Lets Talk LTE Interference

Post by NOYB »

Have you actually measured the frequency response. Others have.
I have that device. I can see the label for myself. Labels are marketing, not specs.
I have copy of the spec sheet as well has actual measurement results done by a third party.
You obviously have access to necessary equipment to do actual side by side measurement comparison with the SD filter instead of just citing what the label (marketing) says. Why don't you?

signcarver
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Re: Lets Talk LTE Interference

Post by signcarver »

For me the channelmaster did indeed negatively affected things on 35 and 36, SD's filter did not even though being told that it (CM) should be 608.

nickk
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Re: Lets Talk LTE Interference

Post by nickk »

NOYB wrote: Tue Feb 16, 2021 1:25 pm Have you actually measured the frequency response. Others have.
I have that device. I can see the label for myself. Labels are marketing, not specs.
I have copy of the spec sheet as well has actual measurement results done by a third party.
You obviously have access to necessary equipment to do actual side by side measurement comparison with the SD filter instead of just citing what the label (marketing) says. Why don't you?
We have the problem of educating customers that they need to choose an LTE filter that passes 608MHz and blocks 618MHz. This is because there are a number of Chinese brand filters that pass to 600MHz but block channel 36 and cause significant problems for channel 35. These filters are not suitable for the US market but are still imported and sold as LTE filters.

The CM filter I tested works pretty well but we can't officially recommend a filter where the printed specs are the exact thing we have to warn customers to avoid - even if, as in this case, the filter is usable while the specs printed on it are wrong.

Hopefully CM will fix their labeling at some point. I like their amplifier products.

NOYB
Posts: 189
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Re: Lets Talk LTE Interference

Post by NOYB »

signcarver wrote: Tue Feb 16, 2021 1:37 pm For me the channelmaster did indeed negatively affected things on 35 and 36, SD's filter did not even though being told that it (CM) should be 608.
Frequency response comparison should be able to confirm that. But the only frequency response comparisons that seem to be publicly available do not. Suggesting that there may be other factors.

NOYB
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Re: Lets Talk LTE Interference

Post by NOYB »

nickk wrote: Tue Feb 16, 2021 2:10 pm
NOYB wrote: Tue Feb 16, 2021 1:25 pm Have you actually measured the frequency response. Others have.
I have that device. I can see the label for myself. Labels are marketing, not specs.
I have copy of the spec sheet as well has actual measurement results done by a third party.
You obviously have access to necessary equipment to do actual side by side measurement comparison with the SD filter instead of just citing what the label (marketing) says. Why don't you?
We have the problem of educating customers that they need to choose an LTE filter that passes 608MHz and blocks 618MHz. This is because there are a number of Chinese brand filters that pass to 600MHz but block channel 36 and cause significant problems for channel 35. These filters are not suitable for the US market but are still imported and sold as LTE filters.

The CM filter I tested works pretty well but we can't officially recommend a filter where the printed specs are the exact thing we have to warn customers to avoid - even if, as in this case, the filter is usable while the specs printed on it are wrong.

Hopefully CM will fix their labeling at some point. I like their amplifier products.
CM has changed the label.
Nobody asking you to recommend a competitor's product.
But you were clearly aware of label vs. spec/measured frequency response and still tried to pass it off as the label being the spec/frequency response. To me that is disingenuous.
If you want to pit your product against their product then do so in a head to head performance comparison. Not by citing labels/marketing.

nickk
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Re: Lets Talk LTE Interference

Post by nickk »

signcarver wrote: Tue Feb 16, 2021 1:37 pm For me the channelmaster did indeed negatively affected things on 35 and 36, SD's filter did not even though being told that it (CM) should be 608.
Out of interest, how long ago did you buy the CM filter?

I have to wonder if they quietly adjusted the frequency range from 600MHz to 608MHz at some point and didn't update the label.

nickk
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Re: Lets Talk LTE Interference

Post by nickk »

NOYB wrote: Tue Feb 16, 2021 2:18 pm But you were clearly aware of label vs. spec/measured frequency response and still tried to pass it off as the label being the spec/frequency response. To me that is disingenuous.
If you want to pit your product against their product then do so in a head to head performance comparison. Not by citing labels/marketing.
When a frequency range is printed on a filter I consider that to be the spec and the expected frequency response. Anything else is disingenuous.

Once the filter has been designed with the right frequency specs for the US market there won't be much difference between filters. We designed and released the Silicondust LPF-608M because at the time there were no other LTE filters that advertised the right frequency specs for the US market.
NOYB wrote: Tue Feb 16, 2021 2:18 pm CM has changed the label.
Thumbs up.

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