Topband: Toroidal common mode choke

[Tom W8JI]

> On paper I agree but what about real world? Topbanders seemed to do quite 
> well with the old 43 mix and the resultant lower impedance.
>
> How much is good enough?

That's a good point.

It seems we tend to go to extremes of black and white and abandon common 
sense or reasoning in everything we do these days. That pattern has crept 
into some very simple things, perhaps so one answer fits all and no one ever 
says "it depends".

> I havent changed any of the 43 material in the house since they removed 
> the noise from each consumer device; some have been in place for over 30 
> years going back to the prior QTH. As new stuff is added I use 31 mix, 
> seems to work the same.

I've never been a big proponent of peppering a system with beads, because 
often a common-mode series impedance by itself is the least efficient way to 
do mitigation. It takes a terrible CM signal levels to cause problems, if 
connectors are good and the antenna is a reasonable distance away. If the 
antenna isn't a reasonable distance away, then correcting the source is 
often better.

It's really a big soup of things, and I think some of this has gone beyond 
sensible solutions. I lived years without problems without any ferrite 
cores, BUT I grounded feeders sensibly and looked at the system. It all 
about ratios and changes in CM impedances.

Once something fixes something, it all seems the same. After all, fixed is 
fixed.

Correct me if I am wrong, but it seems we think noise all comes from common 
mode and if we add increased suppression things get better and better with 
nearly no limits. We become almost anorexic with suppression. What really 
happens is once antenna noise dominates, which can even happen without any 
suppression at all in many systems, all the rest is a wasted effort. In 
other systems once the feedline has reasonable suppression, direct radiation 
takes over. We can add a billion beads to the feeder and nothing changes.

There should be more focus on telling people how to find problems, and less 
on treating every system the same.

I was visiting a friend and he told me stories about building massive bead 
strings a few feet long on Yagi antennas!! Someone should stop the bead 
madness enveloping us, and get us back to rational thought.

73 Tom