Topband: 2Wire, Inc. 3800HGV-B Gateway. RFI --Problem fixed for now….

[Frank Davis]

This is a further update on RFI mitigation efforts here related to the 2Wire 3800HGV-B Gateway modem.  This modem is used  for HD  IPTV and internet access over a high speed line. The updated RF hardened 3801 version of this modem refrred to me by K2AV is not being made available here because BellAliant is moving to fibre optics based delivery systems in this area within a few months.

My own mitigation techniques involved placing a number of 2.4" #31 toroids on the power cable for the modem and also the VDSL CAT5 cable that feeds the modem .... I was successful in stopping my line from crashing but only if I limited my ACOM1010 to 500W out on 160/80/40m.  

The BellAliant technician told me that placing the ferrites on the CAT5 feeding the modem caused  a significant number ( hundreds of '000's on a continual basis.) of FEC (forward error correction) events to begin happening on my line.  I was not aware of these errors as they did not present themselves on the TV screens.   The service provider did not like these errors on the line and wanted to eliminate them.  Today the techs visited again and placed a new 3 pair shielded drop wire from the pole to my house. After much investigation and trial and error he installed a TII Network Technologies filter/splitter (http://www.tiinetworktechnologies.com/repository/datasheetlibrary/NYMDS086-0411.pdf) at the point where the drop wire enters the wiring closet a few meters from the shack area.   

He referred to it as a "business filter" meaning it is generally used in business locations were internet access maybe required at a specific workstation and not others.  It splits the line between POTS and Internet .   Only after this filter was placed did the RFI stop and the line would stay up when I run 700W from the amp.  There are still ferrites on the power cord to the modem but not on the CAT5 cable to the modem. The techs explanation was that this robust filter was "blocking" stray RF induced into the house telephone wiring and CAT5 drops coming back from various parts of the house  to the common terminal block in the wiring closet.  Deduced from a couple of hours of isolating various feeds etc.   There is a lot of wire as each room in the house has a CAT5 cable and a telephone drop and RG6 cable.

In any event for now I can run 700W into my Inv L and 80/40OCF dipole without making the line crash.    Still have a bunch of ferrite on the AC lines to the rig and amp and also on various AC power line feeds in the wiring closet where the modem and the house electrical entrance panel is located. 

I pass this on for the info of others facing RF issues with VDSL modems.

Frank VO1HP
www.vo1hp.ca


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Don't have the time to go into my personal extensive experience with this
one, but there is a 2-Wire  3801 gateway now, with improved circuitry,
hugely upsized cache for forward error correction for vast improvement of
error handling, and knowledge of issues with ham band interference.  You
may find that your methods do not get everything, and the 3801 will be your
answer.

Both my own and my next-door neighbor's 3800 would give up the ghost and
reboot with my 1500 watts on 160 and 80.  Much predecessor activity later,
they replaced both our gateways with 3801's and it has been over a year
with ZERO ham related issues.

73, Guy

On Sun, Jan 29, 2012 at 2:35 PM, Frank Davis <fdavis at nfld.net> wrote:

>
 I posted the note below on the 3830 list in my report on results  CQWW160.

>

>
 Today I investigated the problem and discovered the problem existed on

>
 80&40M as well

>
  where I use an OCF Dipole with a 4:1 balun and separate home brew toroid

>
 choke.  On

>
 160 I Use a backyard Inv L with 30 radials of Random lengths and a ferrite

>
 bead choke.

>

>
 The Gateway Router is installed in the wiring closet near the shack where

>
 the AC

>
 entrance and breaker panel is located.  All the CAT5 wiring for the house

>
 also terminates in this

>
 Central point for connection to the router.   I used the SPEEDTEST.NETsite to 

>
 monitor the

>
 High speed line as I adjusted the power in these antennas.  On all three

>
 of these bands the line would

>
 Crash at 100 w output.  The crash on 80&40 was dramatic whereas on 160 the

>
 line ( router) would stop

>
 And then try to recover indicating that the impact of the RF was greater

>
 on 80&40.

>

>
 Upon investigation I found that the output power cord to the router had

>
 been wedged in behind some AC

>
 Power 12/2 wires coming out of the panel.  Just on spec I rerouted the

>
 cable away from the panel

>
 And the AC wires.  To my great surprise upon testing with rig at 100w I

>
 discovered that on 160 m

>
 The line crash had stopped!  With the amp on, the line would crash at

>
 about 300w.   So on 160m some kind of

>
 common mode currents we're induced into the router power cable just by its

>
 proximity to the

>
 Household C wires!   By the way on 80&40 the dramatic line crashes did not

>
 stop by the

>
 Change in location of the power cable. (OCF dipole used on these bands)

>

>
 To cut to the conclusion I proceeded to use all the 2" toroids (#31

>
 material) I had on hand plus some

>
 #43 snap on beads to isolate as many AC power cords as possible in the

>
 shack....in particular

>
 The AC lInes to the rig and amp and the router power block.  Guess I

>
 should have done this

>
 previously. The greatest impact was realized I when I used three toroids

>
 in a stack and would the

>
 CAT5 cable from the high speed line modular jack to the router with a many

>
 turns as possible.

>

>
 The line does not crash now at power levels of 500-600w on the three low

>
 bands.  Common mode

>
 Currents were entering the router over its power cable an also the high

>
 speed line CAT5 cable.

>
 I need to place toroids on the drops feeding the TV's and the shack PC as

>
 well.

>

>
 I pass it this experience on in the event that it might help others

>
 encountering similar issues.

>
 I have read K9YC's excellent paper several times and have it to be a very

>
 valuable and practical

>
 Guide.

>

>
 73 Frank

>
 VO1HP

>

>

>

>

>

>
 ____________________________________________________________________________

>
 Limited optg time - self-imposed for domestic bliss! It seems my new

>
 IPTV wireless router (Brand: 2Wire, Inc. 3800HGV-B Gateway)

>
 does not like the ACOM 1010 running at full power. It would crash during

>
 every exchange causing loss of TV and internet access. Sometimes it might

>
 recover between Q's depending. Only after my XYL had retired for the

>
 evening

>
 on Sat could I really get into the contest. Further investigation needed

>
 to see if I

>
 can mitigate the problem.

>

>

>
 Sent from an iPad2

>
 _______________________________________________

>
 UR RST IS ... ... ..9 QSB QSB - hw? BK

>

_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK