[RFI] RF getting into 4-port wirelss router.

[Jim Brown]

On Sun,1/11/2015 8:53 PM, Kenneth G. Gordon wrote:
>> I guess the bigger question is - why is there so much RF in your shack to blowstuff up?
> The router is upstairs from my shack, at least 30 feet away. There does not
> appear to be ANY RF "in the shack", which is in the basement at the other
> end of the house from the router.

Lots of foggy thinking in this thread.

Again, what matters is proximity of the ANTENNAS to the victim 
electronics. If we transmit to an antenna, we SHOULD have RF in the 
shack -- having no RF in the shack means that the antennas are not 
working! When that RF gets into equipment, it is the fault of THAT 
EQUIPMENT or its wiring or both.

There's an antenna system defect that can put more RF in the shack 
without making the antenna work better -- common mode current on the 
feedline that finds a sink in the earth by way of the shack earth 
connection, or to the power system line if the shack lacks that earth 
connection. THAT'S the primary reason for using a beefy common mode 
choke at the antenna feedpoint.

Another point I failed to mention in my earlier post. The DSL signal is 
carried in differential mode on the telephone line as modulation of 
carriers up to several MHz -- that is, IN THE SAME RANGE as our 160M and 
80M band. DSL equipment AND WIRING must be carefully designed and 
implemented to resist coupling onto the differential pairs, AND onto 
wiring inside the DSL equipment (that is, the circuit board). Good board 
layout can strongly reject that coupling, simple dumb mistakes can cause 
VERY STRONG coupling. Henry Ott has a great treatment of these issues in 
the latest edition of his classic EMC text. http://www.hottconsultants.com/

73, Jim K9YC