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
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|