Line filters, which one..?

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TechnoGuy001

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#22152 18-May-2008 17:18

I have 3 line filters in the house and only really need 2 (I think), I have one (pic1 , pic2) for 1 phone in the living room.

and the other (Other2 pic1) which then has the phone/fax plugged in to it and another line filter in the ADSL port which then has a plug in the ADSL port of that one which goes over the roof to the router.

First off the reason I have the "2nd" line filter going into the "1st" is because it seemed to make my sync rate better (= better speed) and I can't plug the "2nd" line filter straight into the main phone-line because the plug on it is the wrong kind :(

Is the "2nd" line filter even a line filter....?

Question 1:

What exactly does a line filter do?

Question 2:

Do some line filters work better then others? if so which one do you recommend?

Question 3:

Am I supposed to have a line filter for just a phone? (but the line filter I have has both ADSL and phone ports on it)

Question 4:

I think thats all... for now.

Note: When I say "1st" or "2nd" I am talking about these 1st and 2nd ---\/

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#131697 19-May-2008 08:45

Hi, firstly voice and DSL signals share the same line, but use different freuquenies, voice uses 300-3400Hz, and DSL 25kHz through to 1.1MHz (or 2.2MHz in ADSL2+).

A DSL filter has two primary functions, this first and most important is to isolate POTs devices (Plain Old Telephone service) such as phones, Fax modem, old analog dialup modems, alarm systems, Sky decoder modems (all these various modems are just standard old analog voice band modems running at anywhere from (1200-56kbuad). All these voice band devices will typically short out frequencies above 4-5kHz, therefore effectively snuffing out the DSL signal. There degree of shorting can change and is often more dramatic during the lifiting of the handset, and when ringing is present.

Secondly the filter prevents DSL energy from being heard in POTs devices, ie without the filter you would hear quite clearly a swishing type sound, even with a filter a small residual can remain.

I should point out that a filter is only placed between the line and a POTs devcie, the DSL modem connects directly to the line. All the splitters/filters you show have both phone and DSL outputs, the DSL output is just the input line, ie a direct wire from input to DSL port. Therefore putting two filters in series as you have should not really cause any real problems, as you are just adding an extra bit of wire.

Some filters are better than others and this becomes more important the longer the line, I note your sync speed is quite low, what line attenuation and signal to noise does your modem report. The best solution is to install a central filter, there is only one Telecom certified filter (MM3200B, cost around $50-60 and need to be hard wired to the house wiring), these should be placed as close to the demarc (line entry point) as practical or at or before the first phone socket in the house. From there a seperate pair should be run to the site of the modem, you could use a 2nd pair in the phone cable to create a direct DSL only line to the modem.

Once concern I would have is you show a line cord that you say goes across the roof to the DSL modem, how long is this, flat line cords are not suitable for inserting in a DSL line for lengths more than 1-2meters.

Cyril

TechnoGuy001

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#131705 19-May-2008 09:45

Once concern I would have is you show a line cord that you say goes across the roof to the DSL modem, how long is this, flat line cords are not suitable for inserting in a DSL line for lengths more than 1-2meters.

It's about 7-10 meters. I guess thats a little long then.

I note your sync speed is quite low, what line attenuation and signal to noise does your modem report.
The sync speed ("Connection Speed") moves around alot, one day I can have 3776 (as right now) and another I can have 2100.

There probaly wont be any changes in our set up untill the weekend, too busy in the week :(

webwat

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#131953 20-May-2008 00:33

Your attenuation (and therefore distance from your place to Telecom) is quite high already so you want to plug your ADSL modem in directly to the jackpoint. Run an ethernet cable over the roof to whatever equipment your computers connect to — you might need to buy a cheap 5 port ethernet switch for the other side of the roof.

Why you have a 2nd RJ11 filter plugged into the unfiltered "DSL" port of your 1st filter beats me. Filters essentially block the phone noise from interfering with your ADSL, so you must plug every telephone/analogue/POTS type equipment into a filter one way or another. Try to get them tidy because eventually you will have a problem, and somebody at your ISP will ask you to check whats plugged into filters and whats not (I doubt anybody in your flat could give a straight answer with such a tangle there). By the looks of your tangle, I would keep it simple and plug every phone into its own filter. If you dont have a jackpoint for each phone, then use an adapter to share a single filter among 2 or 3 phones.

Perhaps we need a standard answer for this question because it comes up so frequently.

Time to find a new industry!

TechnoGuy001

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#132139 20-May-2008 18:52

Ok, I moved the router/modem around the house, to all the phone ports and had all phones unplugged and tried the internet on all of them and none of them had any change in sync rate, all where around 3616 - 4000.

So having the modem on that side of the house and using a LAN cable to my room, wont make any difference in speed, well none that is worth all that money.

I am still going to buy a Linksys modem/router and see how that goes (people say it makes some difference in speed, so I am hopeful :)

Thanks for your help thou.

cyril7

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#132141 20-May-2008 19:03

Hi, one real test you need to do, is to identify the first phone point in the house, most likely the Master one if still on 3wire cabling. You then need to plug you modem into that and remove the ongoing cable to the rest of the house wiring, so the cable stops at that point.

Your attenuation and S/N figures should provide line rates nearer to 6Mb/s, therefore it may be that some of the house wiring is providing unwanted reflections that are causing nulls in some carriers.

Cyril

TechnoGuy001

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#132146 20-May-2008 19:13

cyril7: Hi, one real test you need to do, is to identify the first phone point in the house, most likely the Master one if still on 3wire cabling. You then need to plug you modem into that and remove the ongoing cable to the rest of the house wiring, so the cable stops at that point.

Your attenuation and S/N figures should provide line rates nearer to 6Mb/s, therefore it may be that some of the house wiring is providing unwanted reflections that are causing nulls in some carriers.

Cyril

Yea that sounds like a good idea, I will do that in the weekend and post the results here.

You guys are much more helpful then Orcon was. I once emailed asking if I could do anything to get better speeds, and they said I was already getting max and thats about it :(

cyril7

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#132147 20-May-2008 19:18

If you do as described above, and assuming the cable from the demarc to the first socket is in good condition and cat3 (white sheath with two pairs within orange/white and blue/white) or standard telecom gel flooded black Ext 026 (underground) or Ext 026A (aerial) or a mix thereof then this will be the best you will get without getting Telecom to check out their side of the cabling.

Do you have any idea of the approx distance from your house to the local exchange, 47dB would indicate around 3.5km, does this add up or would it be significantly different to that.

Cyril

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TechnoGuy001

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#132149 20-May-2008 19:31

cyril7: If you do as described above, and assuming the cable from the demarc to the first socket is in good condition and cat3 (white sheath with two pairs within orange/white and blue/white) or standard telecom gel flooded black Ext 026 (underground) or Ext 026A (aerial) or a mix thereof then this will be the best you will get without getting Telecom to check out their side of the cabling.
Cyril

We shell see.

Do you have any idea of the approx distance from your house to the local exchange, 47dB would indicate around 3.5km, does this add up or would it be significantly different to that.

Well im not to sure but when I come home everyday I see a white ish box, which I think is it (I'll make a photo tomorrow) which could be about 3.5km if the wireing goes thou the other side of the street then comes to mine. looks like this:

cyril7

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#132152 20-May-2008 19:45

So what you are saying is the box is just down the corner <500m away and that box is 3-4km from the local exhange. What is more important is the code on the side of the box.

It could be that that box contains a remote access unit including a Conklin remote DSLAM, or maybe not. If it does not contain a Conklin then your line may be routed via that box directly back to the HVN (Havelock) exhange, so the line length may be 3-4km. If there is a Conklin in that box then you line attenuation would be only 10-20dB. So it sound like the former.

If the box has one of the following codes on the side then it is due for cabinetisation late next year so you should get very good speeds (ie >20Mb/s) once that happens assuming you are closer than 1km to that box.

HVN/AA, HVN/AD, HVN AF, HVN/AP, HVN/AQ, HVN/AR, HVN/AU, HVN/F, HVN/J, HVN/R.

Cyril

TechnoGuy001

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#132165 20-May-2008 20:35

So what you are saying is the box is just down the corner <500m away and that box is 3-4km from the local exhange. What is more important is the code on the side of the box.

I really wouldn't know where the local exchange is and if that box is even to do with the internet, but I will try and have a look closer look at it tomorrow.

If the box has one of the following codes on the side then it is due for cabinetisation late next year so you should get very good speeds (ie >20Mb/s) once that happens assuming you are closer than 1km to that box.

HVN/AA, HVN/AD, HVN AF, HVN/AP, HVN/AQ, HVN/AR, HVN/AU, HVN/F, HVN/J, HVN/R.

I shell have a look at that too tomorrow. (lets hope it's on there!)

TechnoGuy001

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#132544 22-May-2008 14:27

YAY it's "HVN/AA"

cyril7

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#132545 22-May-2008 14:37

Hi, assuming you are on that cabinet, reasonable but not always confirmed assumption, then you should be good. However have you done the test I mentioned.

Also, can I suggest that you rescale your images to a max width of around 500pixels, and compress them so they are at least a 10th their current size, page will load faster, internet will run faster etc etc

Cyril

TechnoGuy001

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#132548 22-May-2008 14:48

However have you done the test I mentioned.

This one: Hi, one real test you need to do, is to identify the first phone point in the house, most likely the Master one if still on 3wire cabling. You then need to plug you modem into that and remove the ongoing cable to the rest of the house wiring, so the cable stops at that point.

Not yet, I will get that done in the weekend.

Ah yes sorry about that, resized them (60% compression to, was at 80%).

TechnoGuy001

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#133030 24-May-2008 16:12

Ok done the test:

There is nothing on the phone line now, just the ADSL modem, and this is what we get:

I got up to 620KB/s !!!

Note: The "Noise Margin" has gone back up to 11-12 db and I haven't touched a thing.

manhinli

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#133034 24-May-2008 17:03

TechnoGuy001: Note: The "Noise Margin" has gone back up to 11-12 db and I haven't touched a thing.

That's good - a higher SNR is a sign of a good connection. I've got a SNR of 15dB DL, 11dB UL.

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