Topband: 160m noise

[Garry Shapiro]

I modified a 100 kHz Loran loop to 1.85 MHz, mounted it on ski racks on my
car and cruised the neighborhood looking for low frequency noise
sources---those rolling off below 4 to 7 MHz, which are not usually expected
to be due to power company hardware. The loop exhibits a very sharp null,
which I have not previously had the use of in tracking 160 noise.

I found that most poles with transformers--and ground wires to the
transformer--are radiating, but that they vary greatly in amplitude. Some of
these sources appear perhaps to emanate from telephone lines (!)---ADSL? But
the big surprise was to return home and get a huge indication from....my own
shack. The source was my LInksys 4-port Router/Switch---or the Network
Interface Cards (NIC's) in the computers. The noise appears to be common
mode radiation remanating from the CAT 5 cables connecting the computers to
the router/switch.

I presume--but cannot be certain--that the CAT 5 cables, consisting of
twisted pairs, are reasonably balanced at 1.8 MHz. If this is a reasonable
presumption, the radiation must be due to source or load impedance imbalance
in either the NIC's (the same in each computer) or the Linksys
router/switch. The cable radiation is picked up by my antennas, a conclusion
based upon:

* the radiation is detectable >>100m away.
* the resultant interference is somewhat different with each lowband
antenna.

My problem is that I cannot conclusively identify the NIC or Linksys as the
culprit without wholesale substitution. My inquiries to Linksys have
resulted in the usual nonsense one receives from "Technical Support" (sic)
from vendors. In this case, Linksys regurgitated Part 15 back to me and
suggested a firmware upgrade (!) This is reminiscent of outsourced foreign
tech support people telling you to reboot Windows. I do not seem able to
convince them that this is a hardware problem.

Has anyone on this reflector experienced a similar problem? Can anyone offer
some insight --specific or general--re signal performance of NIC's or
routers in this context?

I ask this before replacing both the NIC's and the router.

Garry, NI6T