topic Re: Interesting effect of double filtering the phone - any thoughts in Broadband

Interesting effect of double filtering the phone - any thoughts

Oldjim — Mon, 16 May 2011 13:17:28 GMT

I went over to help one of my referrals who was having trouble with noise on the phone line.
As usual I took along a spare router/filter/corded phone etc.
Using the quiet line test with my phone there was no noise with or without the broadband connected.
Trying with their DECT phone gave a similar result.
I then tried with their main corded phone which is a special high amplification unit for the hard of hearing (I think it isn't UK phone as it uses a USA connection with an adapter) and at normal levels no problems with or without router connected but once the amplification was increased above half way there was a lot of crackling when the router was connected. I checked this with two different filters (a Speedtouch and a D-Link) with no improvement but then tried with the filters in series and the noise went away completely.
I must admit that I don't understand it but at least the problem was solved.

Re: Interesting effect of double filtering the phone - any thoughts

billnotben — Mon, 16 May 2011 13:28:13 GMT

Strange one that as everyone and their dog always say double filtering is a big no as they are supposed to cancel each other out or something else equally detrimental.
Just goes to show that trying any off the wall idea sometimes unexpectedly works.

Re: Interesting effect of double filtering the phone - any thoughts

HPsauce — Mon, 16 May 2011 13:57:27 GMT

No, double-filtering is GOOD!
Provided you do it right......
Many devices, typically SKY boxes, cause fewer problems when double-filtered.
The rules are simple:
plug the phone cable (or other suspect device) into a filter
plug that filter into a 2nd filter
plug that filter into the wall socket
The broadband cable MUST be in the filter directly plugged into the wall socket (i.e. not shared with the double-filtered phone)

Re: Interesting effect of double filtering the phone - any thoughts

stevewilk — Mon, 16 May 2011 14:06:49 GMT

Had crackling on my phone line for years kept having a go at SKY because you couldn't hear it with the router switched off changed to plusnet was still there even in test socket.
I changed master socket because even with the faceplate off there was still some sort of resistor inside. No more problems £9.99 from Maplins
Sorry SKY .
Steve

Re: Interesting effect of double filtering the phone - any thoughts

billnotben — Mon, 16 May 2011 16:46:15 GMT

Thanks HPsauce I get it.
Double filter phone = good
Double filter router = bad

Re: Interesting effect of double filtering the phone - any thoughts

198kHz — Mon, 16 May 2011 17:13:49 GMT

Interesting, Oldjim. Not come across that before, but I'd guess that perhaps some part of the amplifier circuit goes into RF oscillation at higher gain settings, either through a fault, or bad design.
If so, then the level of the RF is presumably high enough to pass one stage of filtering but not two.

Re: Interesting effect of double filtering the phone - any thoughts

markg140 — Mon, 16 May 2011 17:19:11 GMT

Typically the filter that ISP's provide with their service aren't of a terribly good quality.
We use ZyXel quality filters for all our circuit installs at work, much better than the standard rubbish tbh. Not saying it's gonna make a huge difference but always better to be using higher quality components.

Re: Interesting effect of double filtering the phone - any thoughts

HPsauce — Mon, 16 May 2011 18:27:35 GMT

Quote from: billnotben
Thanks HPsauce I get it.
Double filter phone = good
Double filter router = bad

Well sort of.
The phone outlet is filtered, the router outlet is unfiltered.
So plugging a router cable into the router socket of a second filter means it's actually filtered once.
Which is usually enough to kill it.

Re: Interesting effect of double filtering the phone - any thoughts

w23 — Tue, 17 May 2011 22:12:52 GMT

I have a different reason for double-filtering: my two-way phone adaptor (tequired for the phone + sky box) blocks the ADSL port on my ADSLNation faceplate, a 'dangly' filter moves it out of the way. I really should invest in a different shaped adaptor.

Re: Interesting effect of double filtering the phone - any thoughts

HPsauce — Wed, 18 May 2011 07:56:43 GMT

Quote from: walker23
I really should invest in a different shaped adaptor.

Leave it alone.
Double-filtering Sky boxes is a GOOD thing to do.

Re: Interesting effect of double filtering the phone - any thoughts

davidj66 — Wed, 18 May 2011 08:21:10 GMT

Quote from: HPsauce
Leave it alone.
Double-filtering Sky boxes is a GOOD thing to do.

The BEST thing to do with a Sky box is disconnect it from the phone line until you need to use interactive services. Sky don't care unless you have multiroom.
jim:green quote fixed mod:end

Re: Interesting effect of double filtering the phone - any thoughts

Anonymous — Wed, 18 May 2011 08:34:13 GMT

I know nothing about SKY boxes, but from the fact that you are describing the connection being made to the phone line then I assume that they contain an old style dial up modem.
So rather than attempting to over filter a piece of equipment that is causing apparent interference, would it not be better to make the connection another way ?
Would a SKY box be able to communicate via a VoIP adaptor, so you plug the SKY box into the VoIP adaptor's phone socket (unfiltered), and plug the other end into you router.
If this works then it would have the following benefits -
1) Potentially better ADSL as interfering device is no longer connected to the phone circuit.
2) SKY calls would be cheaper or free as they would be going via VoIP, especially if you get free Plusnet minutes on your broadband account.
3) Your landline phone will be free at all times as the modem wouldn't need access to the phone line.
4) No dodgy wiring issues due to double filters, or long extension phone cables to the SKY box which will be prone to interference from nearby TV, DVD, VCR, PVR, etc.

Just a thought

Re: Interesting effect of double filtering the phone - any thoughts

w23 — Wed, 18 May 2011 09:38:38 GMT

Quote from: davidj60
The BEST thing to do with a Sky box is disconnect it from the phone line until you need to use interactive services.

I did have it (Sky+ HD) disconnected for a while but after a few months it stopped working (said 'no signal'), I thought it was broken but I just happened to try reconnecting the phone line, I guess it 'phoned home' to verify my account status or something and the picture came back. I don't think these will work via a VOIP line as I'm sure the Sky small print says it must be connected to a BT landline.
The best thing to do with a sky box is probably to throw it out of the window (after disconnecting the telephone line) and cancel the subscription then spend the money on something more useful.

Re: Interesting effect of double filtering the phone - any thoughts

adamwalker — Thu, 19 May 2011 09:15:14 GMT

Quote
Double filter router = bad

The router side of a filter is just a pass-through so I can't see how that would cause a problem.

Re: Interesting effect of double filtering the phone - any thoughts

Oldjim — Thu, 19 May 2011 09:20:43 GMT

Except that a filter connection wouldn't fit to the router side of the first filter so bad

Re: Interesting effect of double filtering the phone - any thoughts

edgeways — Thu, 19 May 2011 10:38:09 GMT

Hi old jim,
Just noticed this thread.
For what its worth, I have been using double filtering for a long time (only one phone in use- a dect )
I found that it gives me a slight improvement to snr, which is very welcome on my long line.
Mike (edgeways)

Re: Interesting effect of double filtering the phone - any thoughts

HPsauce — Thu, 19 May 2011 10:49:18 GMT

Quote from: _Adam_Walker_
I can't see how that would cause a problem.

Just plug 2 together and look again, you'll see.

Re: Interesting effect of double filtering the phone - any thoughts

MJN — Thu, 19 May 2011 12:33:34 GMT

It might be more helpful, particularly for those that don't have/use plug-in filters, if you would explain what the observed problem is (and the reasonings why if you happen to know).
Mathew
jim:quote

Re: Interesting effect of double filtering the phone - any thoughts

Oldjim — Thu, 19 May 2011 12:36:43 GMT

Quote from: Oldjim
Except that a filter connection wouldn't fit to the router side of the first filter so bad