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  Satellite Internet forum › Wireless Internet - WiFi and WiMax › Filters to stop 5G interference into 4 GHz satellite downlinks.
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Filters to stop 5G interference into 4 GHz satellite downlinks.

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Admin1
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Dec 16th, 2019 at 11:35am  
In Nov 2019 the USA FCC chairman announced a proposal to sell 280 MHz of satellite frequencies (3.7-3.98 MHz) to 5G operators. The frequency sale auction is proposed starting late 2020.

This means that the only C band satellite range left clear is  4.0 to 4.2 GHz.

If the above comes to pass then a 5G base station transmitting in 3.7-3.98 MHz near a C band receive dish will cause severe interference into a broadband 3.625-4.2 GHz satellite receiver LNB.

You may already be using a pass band filter 3.7-4.2 to reduce WiMAX interference.  All tx/rx VSATs need a 6 GHz stop band transmit reject filters in front of the LNB to prevent damage to your LNB from your own transmit signals.

If you become affected by this interference problem then to stop this 3.7-3.98 MHz interference getting into your C band LNB you will need a new filter, but this will also stop you receiving C band signals below 4 GHz!

Advantech have developed pass band filters 4 - 4.2 GHz and 4.02 - 4 GHz. These are rectangular waveguide devices suitable to insert in front of the LNB. Flange: UDR40 CPR-229 FLAT.  Flange: PDR40 CPR-229 GROOVED.

The spec and pictures are here:
https://advantechwireless.com/wp-content/uploads/2019/12/PB-AWT-IRF-C-001-19339....

What is not clear is if the filter also acts as a 6GHz stop band filter for transmit reject purpose, so ask about this.

I hope this attempt by 5G to grab satellite frequencies only applies to the USA.

Best regards, Eric
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Reply #1 - May 11th, 2020 at 11:58am  
Bandpass filters to protect C band receive dishes from 5G interference

News from AsiaSat: 29 April 2020

Asiasat have developed waveguide bandpass filters to be inserted before the LNB at C band receive sites. There are critical for sites at teleports and cable TV headends.

...
Asiasat Link

Among AsiaSat’s bandpass filters, which have been developed locally, the BPF-3700S model was the first in the series launched and designed for the 5G spectrum requirements for Hong Kong SAR and China markets.

Other models include BPF-3800R and BPF-3800S for South Korea and Australia, BPF-3900S for the Middle East, with models BPF-3664, 3600, 3700T and 3900S lately introduced for other Asia-Pacific markets, providing optimised rejection and passband to reject 5G spectrum up to 3.6, 3.7 and 3.8 GHz.

I don't know the specifications or where to order these filters. If anyone knows please add your comment below.

Note that these filters have waveguide interfaces and are suitable only if you have a C band dish with waveguide connected LNA or LNB.  If you have an integrated LNBF as is typical for the many thousands of home and commercial TVRO sites then these filters are not for you.
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« Last Edit: May 12th, 2020 at 3:43pm by Admin1 »  
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Email me: eric@satsig.net

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