Topband: A ham who uses his own weight in ferrites

Tod -MN tod at
Mon Jan 4 13:31:13 PST 2010


I marveled at the number of ferrite cores as well when I first read the
article. Re-reading it I think I found that he lived very close to an AM
broadcast station which seemed to have common mode signals on everything.

I think he went a bit overboard -- at least from the point of view of
someone who does not have that much common mode interference. To eliminate
the common mode stuff he generated I would think a lot fewer cores would be

I am still thinking about how best to pick up small amplitude common mode
signals and look at them with a spectrum analyzer. That, I would think,
might really give one a good idea about just how effective the ferrite core
chokes are. Regrettably, my test equipment is in Idaho and I am in Minnesota
this month so I can do nothing but speculate. Maybe in February I can see
what my common mode issues are, if any,

I do use type 31 cores and have measured the effects of 1,2 3 and 4 turns
through the DX Engineering large beads. They are very good at choking RF on
80m with 3 turns and even better with two beads in series each with three
turns of coax through it. In series means that each bead forms a choke and
the chokes are in series not that the same turns go through both of the

73, Tod, K0TO

> -----Original Message-----
> From: topband-bounces at 
> [mailto:topband-bounces at] On Behalf Of Carl Clawson
> Sent: Sunday, January 03, 2010 12:52 PM
> To: Topband Reflector
> Subject: Topband: A ham who uses his own weight in ferrites
> I stumbled across this article on common mode noise somewhere:
> Looking at the extensive choking at this station, I am 
> astounded. For example, I've never heard of anyone choking 
> entire mains branches at the breaker panel (his Fig. 14). 
> Maybe I just haven't paid enough attention.
> But...
> Not that I plan to start knocking holes in my walls and 
> filling junction boxes with ferrite any time soon, but I'm 
> curious how far others have had to go.
> 73 & thanks,
> Carl WS7L
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK

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