BartC wrote:
"tony sayer" wrote in message
...
In article , BartC scribeth

I never solder those things, and I expect the tiniest amount of
capacitance
will do the job. Actually, I often only have to hold the plug near
the RF
socket on a TV, and I start to get a picture, on an analogue set at
least.

(In fact, I'm just done a test on a digital TV, disconnecting the RF
lead at
a joint: if the outer screen is in contact, I start to get a picture
when
the inner core is 2 or 3 mm away from the centre pin! So the signal
can jump
an air gap of a tenth of an inch, and from one point to another,
while an
unsoldered wire will have a 1 or 2cm length in a hollow tube so a
greater
capacitive effect)


Sorry but thats not very good practice or science come to that. If in
the RF I work in we had unsoldered joints there would be fires and
smoke;!..

The signal from a TV aerial is at microscopic power levels. And I do
tend to bend the inner core of the coax to make sure it makes contact
inside the hollow pin of the plug.

But if it doesn't, doesn't it just form a tiny capacitor? (And I
wouldn't be surprised if the first thing the signal encountered inside
the TV was an actual 10pf or 100pf series capacitor.)

10pf is a fair bit more than a wire inside a hollow pin.

And the FIRST thing is generally a 75ohm load, actually.

If the cable is separated from that, you can get nasty cable resonances.
Especially on LONG cables........