[RFI] ADSL carrier frequencies

HP pfizenmayer at q.com
Wed Jan 10 01:35:36 EST 2018

Are there any ADSL gurus out there who can help me understand what is going on . 

Everything I read about DMT ADSL is that the subcarriers are 4.3125 khz. spacing . 
Also the comment is that it will appear as wide band noise since the carriers amplitude 
and phase are rapidly changing . 

Here in Phoenix / Centurylink my area has overhead wiring . - I have carriers at 
precisely 4 khz spacing for instance on 40 meters - 7004.783 , 7007.783 ,7015.783 etc etc. 
If there is "wideband noise" on 40 meters - I cannot seperate it from my ambient . 

I do have severe wide band "hiss" starting below 20 meters and extending thru 15 meters 
which might be VDSL - this noise raises my ambient about 15 dB as I swing the beam toward 
the source or have it off the ends of the elements. 

About a year ago the carriers were extremely strong on 160 meters (as much as -75 dBm) 
and had the same 4 khz spacing . Tthese were finally reduced to close to my ambient noise level 
after months of hassles with Centurylink even after a Denver Engineer had identified the exact 
customer source of the carriers by turning off customers as I monitored the carriers . I had identified 
that area to one of two houses myself with my handheld 160 M DF setup. 
The issue was a modem feeding an open pair to that customer which made it run wide open . 

Recently a new cable was run and now there are 40 meter carriers as above 5 to 15 dB out 
of my ambient noise of about -110 dBm .There are apparently several sources .since I can 
null different sets of carriers off the ends of my rotatable dipole at different bearings. 

I hope the reflector does not remove all paragraph spaces . 

Hank K7HP 

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