I recently experienced Bluetooth noise on a cheap Chinese AC-DC Integrated Amplifier/Radio/Etc. in my shack. As we know by now all the necessary / "unnecessary" components were remove by the manufacturer to save costs. I needed a filter to filter the bluetooth noise coming from the built in bluetooth module. I have a few old ADSL Filters lying around and I decided to test one of these filters to filter the Bluetooth noise. No this is not the ideal filter but I decided to install this filter. Lets first read what is the function of a ADSL filter:
"A low-pass filter, also known as an ADSL filter, filters out all high frequency signals. This ensures that your high frequency ADSL signals do not interfere with voice calls on the same line which use lower frequencies.
Asymmetric digital subscriber line (ADSL) is a type of high speed Internet connection that uses existing telephone infrastructure to deliver Internet service. Telephone equipment like phones and fax machines aren’t designed for ADSL signals. As a result, phones can interfere with Internet connections and vice versa. ADSL micro filters were created to keep normal phone signals and ADSL separated, even though they are running on the same wires. ADSL micro filters are installed between telephones and your phone jack.
ADSL filters prevent your Internet signal from interfering with the voice part of your phone line. When ADSL interference occurs, it typically sounds like a series of fast clicks. ADSL filters also ensure that your lines are terminated correctly by preventing signal reflections that can cause errors on your ADSL Internet connection.
If your ADSL Internet connection works correctly when your telephone equipment is disconnected from your phone line, but stops working when telephone equipment is connected to the line or is in use, then there might be a problem with your ADSL filter installation.
All telephone equipment and other non-ADSL devices that might use telephone lines (like home alarm systems) must be connected to a line that has been filtered at some point. How many filters you need and where they should be installed depends on how your phone wiring is laid out; just make sure that your ADSL modem is not on a filtered line while all other devices that use your telephone line are filtered.
A DSL filter or POTS filter is an analogue low-pass filter installed between analogue devices (such as telephones or analogue modems) and a plain old telephone service (POTS) line, in order to prevent interference between such devices and a digital subscriber line (DSL) service operating on the same line.
Without DSL filters, signals or echoes from analogue devices at the top of their frequency range (low end frequency) can result in reduced performance and connection problems with DSL service, while those from the DSL service at the bottom of its range (high end frequency) can result in line noise and other issues for analogue devices.
DSL filters are passive devices, requiring no power source to operate. A few high-quality filters may contain active transistors to refine the signal."
Now that you know more about ADSL Filters and their function you will realize that it is not an ideal filter for what I wanted to use it for. None the less I installed it and the bluetooth noise disappeared. However in the process I lost a bit of volume (audio) on the amplifier but for my purpose it is doing what I want it to do and the little volume lost does not effect my use of the amplifier.
Having a look at the filter their might be some components that can be used as ("filters") 1:1 transformers in a soundcard interface for RF radios. I have not tested this in practice but will do so when I experiment again with a soundcard interface.
Now onto the title of this topic: "Any other uses for ADSL Filters lying in the junkbox? If you have any suggestions please share them with us.
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