[RFI] 160M RFI - 4 khz combs-

HankP pfizenmayer at q.com
Sat Dec 19 23:45:59 EST 2015

RE: the earlier message about 160 M carriers popping up with keying 

I found the following about VDSL2 : 

DMT divides signals into 247 separate channels, each 4 kilohertz (KHz, or 1,000 
cycles per second) wide. One way to think about it is to imagine that the phone 
company divides your copper line into 247 different 4-KHz lines and attaches a 
modem to each one. You get the equivalent of 247 modems connected to your 
computer at once! 

Each channel is monitored and, if the quality is too impaired, the signal is 
shifted to another channel. This system constantly shifts signals, searching 
for the best channels for transmission and reception. In addition, some of 
the lower channels (those starting at about 8 KHz) are used as bidirectional 
channels, for both upstream and downstream information. Monitoring and 
sorting out the information on the bidirectional channels, and keeping up 
with the quality of all 247 channels, makes DMT more complex to implement 
than other carrier technologies, but also gives it more flexibility on 
lines of differing quality. 

They do use channels in the 160 meter band and other ham bands and even 
talk about RF ingress issues from hams and RF egress to hams. 

Sounds like what I may have - although I have not hard any modulation on those 
carriers , perhaps they are just "holding places" . Question is why it just started up 
a few days ago - will try to find out something from Centurylink but they have been 
very hard to deal with on other issues. Unable to ever reach anyone past the filters . 

Walking the alley with a homebrew ferrite rod ant and my little IC R10 rx the carriers do 
peak at each pole that has a drop .COX cable lines also run the same pole line - 
not inconceivable it might be something they are doing . Both plants are really sloppy 
with rats nests of wires and unused drops just cut off and hanging .. 

Hank K7Hp 

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