Re: Topband: 160m noise

[Mike Roden - W5JR <w5jr@bellsouth.net>]

I, too, have the noises on 160 and 10m and 2m.  Same at my Dad's shack.  I 
can almost assure you it is the router.  I can connect a single PC directly 
to the DSL Modem and have fewer issues.  I disconnect the other PC's from 
the router to compare similar to similar.

My best solution for 160 came when I installed an inv-L, further from the 
house.  The dipole hanging from under the eve also hears my TV set's RFI 
pretty bad (none of the Sony's, Samsung or Bose Lifestyle even thump from 
1kw CW just 30 feet from the antenna - truly amazing)

Adding some ferrites helped, especially on the wall-wart power line.  I 
have a couple of really inexpensive hubs that make HF unusable - so I took 
them to the office.

I've not had trouble with 160m RF getting into the Linksys, but the SMC I 
used prior would roll over at anything above 100w - a bad deal if using 
telnet packet cluster during a contest!  The ferrites helped in keeping the 
RF out most of the time.

As for VHF, the only solution was an outside antenna, away from the shack.

At 09:41 PM 11/3/04, Garry Shapiro wrote:
> 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
>
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Mike - w5jr@arrl.net - Alpharetta, GA 

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