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
> (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.
Good move.
73, Jim K9YC
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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