|
Ive been playing at noise mitigation here at WE2 X PQ
Wasilla Alaska and Im pretty happy Ive got 137kHz down to a finite level where I
cant really mitigate it any further - the noise level is effectively S3 per se
and the contributed by sideband noise from Loran and other on air qrm/n.
Sideband noise from Loran is plainly audible.
500 kHz has been another matter - The meter sits at S5 or
so on SSB in 2.8kHz BW - The noise is proven to be from my ADSL ITU
G.992.3 feed from my local Telco - My feed is from an underground (UG)
feed then a twisted pair into the house (of wooden frame construction) then into
a distributed UTP star and seried connections to RJ connections around the house
including my ADSL modem.
The noise bandwidth appears around 150kHz up to 1 MHz
which would appear to be the "downlink' towards me power
bandwidth.
The fix isnt pretty but its to limit the length of the
ADSL feed before it meets an ADSL filter or filters - in my case this is to site
the ADSL modem close to where it comes out of the ground then place the modem
there and then filter the RF out and only feed the audio to 4kHz round the
house. I put a wireless Linksys at the same location of the ADSL modem -
filtering the heck out of power as we go - so all office comms are via
wireless.
Ill let you know how it goes but initial indications are
by effectively shortening the ADSL "antennae" - that the my noise level has
dropped to S2 and this isnt ADSL white noise - I cant distinguish any pattern to
the noise so presume its dispersed by coding.
ps Im limited to 512 K down so this is a pretty expensive
and slowish ADSL connection for those who live in the "boonies" -
So if you have a "Whiteish noise" view of 500 kHz or
MF and you have some negative influence from ADSL.
Laurence KL1 X
| 