"HiFi" speakers have been known to thump in rhythm with the sending of CW when
the amp is OFF!
Not sure what is actually thumping, but the idea of finding a panel that's
doing it might be of value.
* * * * * * * * * * *
* 73 - Mac, K2GKK/5 *
* (Since 30 Nov 53) *
* Oklahoma City, OK *
* USAF, Ret (61-81) *
* * * * * * * * * * *
> From: Gary@ka1j.com
> To: rfi@contesting.com
> Date: Sun, 30 Mar 2014 11:33:17 -0400
> Subject: Re: [RFI] Thumper & not the rabbit
>
> A couple of reasons, Main one is the 97 year old who lives here and
> gets scared and very vocal it will cause damage to the heating unit
> requiring replacement of the part and the loss of heat until the
> expensive repair is done. This is not an unjustified concern &
> demand.
>
> The other is I couldn't feel which part is thumping but more to my
> interest, why is it thumping, it's not a hum, its a loud thump. Some
> electronic component is creating slamming in a way it never does in
> normal operation.
>
> I need to find the problem and address that.
>
> Gary
> KA1J
>
> > Why not figure out exactly which panel of sheet metal is thumping, and then
> > either pull it tight by attaching a thin cable to it with a sheet metal
> > screw and tying it off to a wall, or pushing against it by wedging a 2x4 or
> > something against it?
> >
> > Chris
> > KF7P
> >
> >
> >
> >
> > On Mar 30, 2014, at 1:16 , Gary Smith wrote:
> >
> > Some interesting thoughts. It's for sure RFI that's involved and I am
> > ordering a fairly large quantity of ferrite clamps which I plan to
> > attach to each coax termination & origin in my system. I'll have some
> > left over to try and resolve things like this.
> >
> > The most mysterious part to me is how it is a thumping sound just
> > like a large sheet is energized in a kinetic nature and vibrating
> > against resistance creating a drum like sound using the enclosure as
> > the drum head. Very unexpected. The leads to the unit are pretty
> > tight and I think it would be a good idea to make loops of matching
> > zip cord through the ferrite snap-ons and solder them in series to
> > the existing control wires.
> >
> > This will be a good first step and then mention was made about the
> > unit being properly grounded. I haven't looked at that as it was
> > installed by a local heating company and I will have to be sure they
> > did that.
> >
> > The tribander is at arm level on the top of the roof of this 1 story
> > ranch and if it were higher, there would surely be less rfi to
> > contend with. Can't do higher at this time but I've been considering
> > hardline, I wonder if this would be of more benefit to reduce the
> > RFI? issues or if its the RFI getting into the equipment from wiring?
> > Still, there was a very marked improvement in thumping with that new
> > balun in line.
> >
> > Thank you for the attempts to help.
> >
> > 73,
> >
> > Gary
> > KA1J
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