Jim GM4DHJ ... wrote:

"Roger Hayter" wrote in message
...
Brian Reay wrote:

The Natural Philosopher wrote:
On 10/06/2019 08:15, Brian Reay wrote:
The Natural Philosopher wrote:

A lot of unearathed metalwork floats at 110vAC due to there being RF
filter caps to live and neutral from the metal case.


It shouldn't be designed like that, it is pointless. It doubles the Z
between L&N to dump noise via the C's (C's in series rule) and
introducing
the stray 110Vac point. As I posted in another group, this situation
can
arise due to a fault condition if, for example, the earth at the plug
(top)
is lost or somewhere else before the filter.

It isn't pointless from an RF POV.





Read what I posted, carefully. The two C's would be in series, halving
the
overall value (assuming they are the same), that doubles the impedance Z
to
decouple the noise. One C would between L&N would be more effective and
avoid the stray 110V AC point.

It would be more effective for possible differential noise, but totally
ineffective for common mode noise, which is more likely. As someone
said it is common to have both, as well as coupled series inductors and
further capacitors if it is a posh mains filter.

don't know what you are all arguing about other than you love it and try to
belittle people.....it felt like the voltage that goes up the cable to the
LNB as I have felt it many times sticking my finger across the inner and
outer of the plug...it is not static and doubt if it is the other things you
are discussing...anyway pack it in until I get back down with a new free LNB
....... you all want to show how cleaver you all are except roger and that
is why I keep going on about professionals in ham radio......I think the
voltage is going into the duff side of the LNB ie the dead horizontal and
somehow appearing on the outer of the plugs etc....anyway I will let you all
know and I will tell the truth about my findings......

Sorry to disappoint you, but I find it a little difficult to know how
you get the DC voltage to appear on the cable outer unless that
particular cable is disconnected from the receiver, or one of the
receivers is disconnected from the mains. Unless this is the case I am
going with the majority and guessing you have a faulty LNB *and* a bit
of mains leakage on the receiver chassis. BICBW. See if the tingling
goes when you've replaced the LNB?

--

Roger Hayter