[RFI] ADSL carrier frequencies
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 .
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