Topband: pulse noise

[W7lr@aol.com]

For some time I've experienced pulse noise on 160m.  It occurs on certain 
discrete frequencies and is low level.  I've turned things off in the house 
with no effect.
I have a EWE receiving system giving 6 directions, and the pulse noise is 
greater in one direction (towards Europe from Montana).  Here are some 
examples.
This evening (0130z) the background noise level is between 2.8 and 3.2 (using 
the bar graph s meter of the TS850 and two narrow cw filters).  All pulse 
noises are about s 3.4    This evening the pulses are like long dashes, some 
slight drops in "signal".
In the morning the nature of the pulses are different, for example listening 
for
JT1/K4ZW this morning on 1905.5 the pulses were on/off about 1 second 
duration.
1905 and 1906 were pretty clear.  The background noise level is less in the 
morning, around s1 to s2.  An odd thing are the frequencies where the pulses 
occur.
For example, this evening on 1800.45  1800.82 1801.41  none until tuning to
1814.18 then more on 1824.46 1824.83 1825.80 and no more above that at least 
up into the "ssb" band.  I'm really scratching my head to wonder what could 
cause these or how to attack them.  Any ideas?  73 Bob W7LR