The search of the best filter to buy for a certain case is difficult because the distributors of these components do not provide a comparison of the frequency characteristics of different filters. Having such data would require manual work to get the pictures of the characteristics from the datasheets of the components.
Ideally there should also be tables of values of attenuation versus frequency so we could easily compare two or more products according to their attenuations, but such tables are not found anywhere in the datasheets, and we can bet that if we asked for these tables from the manufacturers of these products they wouldn't want to release these data as for them it is better to force engineers into looking at small and blurred plots until they give up and select a product that just looks good enough.
For this reason we didn't try AC filters before, but recently we found the time and patience to examine almost all the AC filters listed by one of the largest online shops of electronic components in Europe.
We considered only AC filters that are mounted on metal enclosures, we didn't consider filters that have to be soldered to printed circuit boards.
We discarded all the products that didn't have a plot of the attenuation versus frequency, either in picture format or included in the datasheet in PDF format.
We also discarded all products that didn't have a photo of the product, but these were just a few, and are probably not in production anymore, or they are used only in special cases.
Then we collected all the datasheets or pictures, and captured a picture of the attenuation plot for each product.
This was also complicated by the location of the plot inside the datasheet. For brevity the manufacturers group products according to their characteristics but the products must be found by the part number, and one has to go through several pages of plots and tables to find which plot is the correct one for a given part number.
After several days of work we collected a database of about 100 products complete with attenuation plots. Then we used this database to find the most convenient products to buy and try.
There is also the problem of the availability of a product at the distributor warehouse. We have built a connection between our database and the website of that distributor, but only for that distributor.
There is at least another well known manufacturer of AC filters, it is the Schaffner company, but we haven't considered it because the distributor we used doesn't sell all the products of this manufacturer, and because the products of this manufacturer look really like the ones of the other two manufacturers Schurter and TE Connectivity. Maybe in our next work we'll collect data about Schaffner products and see if there are some products that are worth trying.
If you need to select an AC filter then our database of filters characteristics could be useful to you. We now offer this information as a paid service, as we need to sustain our research. Feel free to contact us for prices and other details.
Filters applied to ADSL systems