Broadband filters

George_Michael

My elderly neighbour has recently asked me to have a quick look at their computer and router as their broadband is intermittently dropping off.
I found that they had 2 microfilters plugged into their master box in series with each other and the telephone and router cable were taken from the second filter.


I might be missing something but is there any possible reason why someone would have done this? and could having 2 filters in series cause any problems?
I've removed one of them but as the drop off is intermittent, I won't know for a day or two if this has resolved the snag.

stator

If it works at all then that means the router is on the unfiltered connection. If the phone is on an unfiltered connection then yes it might cause the problem. If the phone is on a filtered connection then I wouldn't expect this to be a major issue. However every cable/device you plug in between the router and the wall point will make the connection a little worse so it could be related. If one of the filters is dodgey then yes it could be the cause. Removing one of them is obviously the right thing to do.

psychic_teabag

AFAIK an ADSL filter is just a low-pass filter for the telephone part, and a high-pass for the broadband part. Presumably the second one is plugged into the telephone outlet of the first one, which should already have had the broadband frequences filtered out. Or at least attenuated strongly.

I can't think why you'd want to do this, and yes, I'd have thought that the broadband would suffer since it has had to pass through a low-pass filter. (Surprised it would even work at all.)

Maybe there's a case for having two filters in series if the phone was being affected, but you'd still want the router to connect to the first filter, so that it hasn't been through a low-pass filter.

MIL couldn't get broadband to work in a particular phone socket. Turns out it was on an extension lead which was plugged into the filtered output of the main socket. So that was in effect the same scenario, though with a length of extension cable between the two series filters. Once I plugged the extension directly into main socket, it all worked fine.

DoaM

Post #3 is essentially correct.

In the OP's situation, it may be that they have an old style master socket - one that doesn't have a split faceplate. OR it has a split faceplate but doesn't have a filtered faceplate fitted. In that situation, having a filter into the main socket and plugging the modem into the ADSL port of the filter should be fine. Similarly, plugging in a 2nd filter (into the phone port) and plugging the phone into the 2nd filter is fine.

Where the problem may lie is if ...

a) There is an extension phone socket wired to the back of the master socket faceplate; if there is a phone plugged into that extension without a filter then that could cause issues;

b) If there is a house alarm hard-wired to the phone line; this is often done behind the master socket and often doesn't include any filter; this could also cause issues.

System

George_Michael wrote: »

and could having 2 filters in series cause any problems?

Yes it could if the cable connecting the router to the filter was in the second filter plugged into the first because the first filter would be filtering out the ADSL signal to the second adapter.

Log into the router, check the system logs. If its not been dropping the connection and the issue is wifi connetivity try changing the wifi channel to anything other than 1,6 or 11 which is the default for most routers meaning half the neighbourhood will be on one of those three.