Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[burakkucat]

I thought the point about the Mk2 faceplate was that it was suitable for VDSL i.e. to 17.7 MHz ?   and though the RF3 had more bandwidth than the RF2 it wouldn't cover that. In fact the bandwidth ratio needed  for VDSL is extremely wide  for any such device and the RF3 is a low frequency core design i.e. not sectionalised or distributed ?

Again, I think a fellow Kitizen recently posted a description of the mode of operation of an RF3 . . . implying that it does not operate as a band pass filter. 

Ah ha! I've just found the thread. And the originator of that thread was (drum roll) . . . JGO!

[JGO]

" So is the consensus the MK2 plate is better than a run-it xte-2005 for keeping out RF on adsl2+? Or would I maybe be better to do xte-2005 + RF3? "

From your point of view you probably need something like that which attenuates even mode pickup on the overhead wires. The modem should have some rejection of it's own but manufacturers are coy about giving figures !
As to which is better,  suggest you need at least week long test with each to decide which is best. ( In my case if the speed is going to drop it is nearly always on a sunday evening, but on average only 1 week in 3.  I just check on monday and if necessarily switch the modem off for 5 secs and swear - most important !)

Now off topic :=
The RF3 etc aren't supposed to be bandpass filters, they are common mode rejectors, BUT  because of the limitations of magnetic cores etc each wire has some leakage inductance which doesn't couple with the other winding. The effect of this is a low-pass filter which limits the bandwidth ( REAL bandwidth in Hz!)  So the design inductance has to be limited, which curtails the low end useful frequency in order to get a desired high frequency performance.  (I understand the RF2, aimed at telephones ?  had to be scaled down for ADSL as the RF3)
VDSL has an enormous frequency range , about 608:1 as against 38 for ADSL1 & 2 and 76 for ADSL2. 200:1 is a more comfortable design range.

So I suspect a VDSL common mode filter is a  compromise - either sacrificing high end performance "The S/N is usually poor anyway at that end so no loss" OR low end " The high end is more susceptible pick up and low frequency interference comes in via power supply anyway".   Measured performance would be useful. 

 

[JGO]

P.S.

The I plate doesn't isolate the master socket as far as ADSL nor does it include micro filters so you need to add them at each socket - fragile ! . Thus a filtered faceplate is better for pickup on the extensions.
Reading the blurb on a Mk2 there is something about working up to 30MHz (?!) so it may be inferior to a MK1 for ADSL as opposed to VDSL. As you say you can always add a RF3 which at least is wall mounting.

Frankly without  test gear it ends up as suck it and see since interference can enter by several routes and you need to clobber them all.  (If it is half by one route you could eliminate one but the level will only drop substantially when you deal with both.)   
Good Luck

[badassgeek]

I had a significant improvement using the MK II faceplate (the vigor 120 I got as well which seems to hold well), there are still some small issues, but i also have an rf3 at hand, i was wondering if anyone had instructions on usage? I have some cat5e to play with so I want to give it a try and see what happens. Thanks :-)

[JGO]

The RF3 goes in the line,  before any splitting for phone and Broadband  but is made with terminal screws. Internally it is screw connections for input and V connectors for output.
 
Important point;  if you do filter the combined phone/BB line - don't put an extra twist as this will invert the polarity of the DC and upset the phone !

I found it convenient to cut a modem cable into two and insert the RF3 in it so I could plug it in and replace  the plain Mk1-faceplate-to-modem cable with a RF3'ed one quickly.  This is just my idea; if you want to screw it to the wall and hard wire it do so.

Incidentally, confirmation from another thread,  the RF2 slowed someone's ADSL speed. It was designed to keep RF out of phone full stop.( Broadband what's that ?) Probably N times as many turns on the coils as the RF3  since there was no need to compromise.     

[badassgeek]

The RF3 goes in the line,  before any splitting for phone and Broadband  but is made with terminal screws. Internally it is screw connections for input and V connectors for output.
 
Important point;  if you do filter the combined phone/BB line - don't put an extra twist as this will invert the polarity of the DC and upset the phone !

I found it convenient to cut a modem cable into two and insert the RF3 in it so I could plug it in and replace  the plain Mk1-faceplate-to-modem cable with a RF3'ed one quickly.  This is just my idea; if you want to screw it to the wall and hard wire it do so.

Incidentally, confirmation from another thread,  the RF2 slowed someone's ADSL speed. It was designed to keep RF out of phone full stop.( Broadband what's that ?) Probably N times as many turns on the coils as the RF3  since there was no need to compromise.   

So A-B as normal on the screw connectors, I guess the unmarked one is A, as I see only B and E that is marked there. Extra twist?

[JGO]

 "Extra Twist ?"
Yes - if you reverse the polarity of the 50v you'll screw up ! One reason I put it in the BB only wiring where no 50v.

Suggest you use something like DSLstats to look at the bits/tone to get an idea what happens to the  response over the bandwidth before and after. If the Faceplate Mk 2 has a RF4 the results might be "interesting" !

[burakkucat]

"Extra Twist ?"
Yes - if you reverse the polarity of the 50v you'll screw up ! One reason I put it in the BB only wiring where no 50v.

  b*cat has to comment. In reverse order:

• The nominal 50 VDC is still present on the pair leading to the modem.
• The polarity of the pair is actually, nowadays, irrelevant as far as any connected equipment is concerned. (Although I always ensure that the B-wire is more negative than the A-wire.)

[JGO]

" The nominal 50 V DC is still present on the pair leading to the modem."

 Quick check with ohmeter and a Microfilter agrees with you !  BUT  WHY ?
That branch is supposed to be  a High Pass filter which blocks DC in my language ? What is the point of extra components, which all cost money  ?

"The polarity of the pair is actually, nowadays, irrelevant as far as any connected equipment is concerned. (Although I always ensure that the B-wire is more negative than the A-wire.) "

OK so it doesn't matter, thanks for the information.

[burakkucat]

" The nominal 50 V DC is still present on the pair leading to the modem."

 Quick check with ohmeter and a Microfilter agrees with you !  BUT  WHY ?
That branch is supposed to be  a High Pass filter which blocks DC in my language ? What is the point of extra components, which all cost money  ?

The only High Pass filter present in the circuit will be inside the actual modem. There is just a Low Pass filter within either a micro-filter or a centralised filter.

Attempted ASCII art:

Code: [Select]

---- Incoming pair ---- Low Pass filter ---- Telephony Circuitry
              |
              |---- Broadband Modem Circuitry


[JGO]

  Corr !



Thank you very much for the clarification.

[Black Sheep]

I love B*Cat ...... he knows everything and makes it easy to understand. 

[burakkucat]

I love B*Cat ...... he knows everything and makes it easy to understand. 

   (Thank you for the complement.)

[roseway]

 

[badassgeek]

How would I avoid reversing the polarity?