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

Jim Brown jim at
Fri Feb 3 20:47:21 PST 2012

On 2/3/2012 3:29 PM, Frank Davis wrote:
> 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 difference between 500W and 700W is only 1.5dB, so if it's clean at 
500W, it should not take much to make it clean at 700W!

> 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.

That does not make sense unless the CAT5 was mechanically distorted by 
the winding.  That would disturb the impedance at bit, but a LOT of 
errors doesn't make sense to me. The ferrites form a common mode choke, 
which the differential circuit should not see.

>    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.

Was it twisted pairs? Twisting is what matters.  CAT5/6/7 is very good 
twisted pair.

>   After much investigation and trial and error he installed a TII Network Technologies filter/splitter ( 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.

Good move.

73, Jim K9YC

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