On 29 Mar 2014 at 12:28, Gary Smith wrote:
> Intermittent anything is hard enough to diagnose but something needs
> addressed. Any thoughts on what I might look at first before I start
> digging in?
My thoughts:
1) adding the good balun reduced the radiation from your feedline, thereby
reducing the level of RF getting to the furnace system.
2) SOMETHING in the furnace system is resonant...to some frequency,
multiple, or submultiple, of a ham band, or even a particular frequency.
Have you investigated trying to find a particular frequency at which this
thumping is worst? (Might be particularly annoying to your family to do so.) If
there is such, that might give you a clue (or "clew" for our UK friends).
FYI, when I am on one particular frequency in the 40 meter band, our GFCI
that feeds the clothes washing maching trips. Also (and I have not yet
tracked the exact frequency which does this) sometimes (there's that word
again...) my operations wipe out all the settings in our wireless router and I
have to reinstall those.
(I have not yet installed the necessary ferrite snap-on chokes on the lines
going into and out of the router, but will.)
Perhaps (as others have mentioned) installing ferrite snap-on chokes on the
thermostat wires, and on every other wire going into and out of your furnace
may help? At least the results of doing that might give you another clue/clew.
;-)
Have you tried making absolutely certain that the entire furnace is properly
grounded?
Is this a hot-air furnance, or a hot-water or steam type? Perhaps, if a hot air
type, a plenum is resonant?
What I find especially intriguing is the MECHANICAL causes of that
thumping. Most innersting. I wonder what that is? :-?
I would be interested to hear if you can MAKE it thump on each key-down
while on CW.
Ken W7EKB
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